The current state of molecular testing in the treatment of patients with solid tumors, 2019
The world of molecular profiling has undergone revolutionary changes over the last few years as knowledge, technology, and even standard clinical practice have evolved. Broad molecular profiling is now nearly essential for all patients with metastatic solid tumors. New agents have been approved based on molecular testing instead of tumor site of origin. Molecular profiling methodologies have likewise changed such that tests that were performed on patients a few years ago are no longer complete and possibly inaccurate today. As with all rapid change, medical providers can quickly fall behind or struggle to find up-to-date sources to ensure he or she provides optimum care. In this review, the authors provide the current state of the art for molecular profiling/precision medicine, practice standards, and a view into the future ahead.
Mục Lục
Molecular Testing and Its Evolution
Comprehensive molecular profiling of patient tumors has been widely studied over the last few years in a variety of cancers, leading to the development of a new discipline termed “personalized” or “precision” medicine. Molecular profiling is becoming standard practice for most patients with advanced disease, replacing the historical treatment paradigm of prescribing standard chemotherapy based upon the tumor’s organ of origin, histology, and stage. This approach has allowed oncologists to reorganize the way they think about cancer and to make treatment recommendations based upon genomic drivers of tumorigenesis. In some cases, this has produced dramatic, positive outcomes, including complete remissions, even in the setting of treatment-refractory disease, delighting both patients and their caregivers.
The molecular profiling field is evolving rapidly. We are now shifting our focus from a few small, predictive, disease-specific, evidence-based tests—chosen “a la carte”—to broader panel testing that measures levels of changes in myriad “genes or gene products.” These genomic changes can serve as biomarkers of both response prediction (indicating tumor and patient outcome/response to a specific therapy) and a patient’s prognosis (describing innate tumor aggressiveness, which aligns with patient survival regardless of treatment received). Increasing numbers of biomarkers have been identified for which targeted drugs are being discovered and exploited therapeutically. Scientific advances go hand-in-hand with technological advances, which lead to improved therapeutic choices, all of which have garnered US Food and Drug Administration (FDA), Centers for Medicare & Medicaid Services (CMS), and insurance company attention. Growing acceptance of evidence-based biomarker testing for the purpose of targeting treatment to solid tumors has ensued. Notably, Foundation Medicine’s FoundationOne CDx assay, which tests for several well-known markers using next-generation sequencing (discussed later in this review), was recently approved by the FDA and concurrently accepted by the CMS.1, 2
To facilitate cancer therapy, it is important to distinguish between germline abnormalities and somatic abnormalities. A very good example of this is the recently incorporated BReast CAncer gene () germline testing for all patients with pancreatic cancer. Germline testing involves an extensive coverage of , whereas current somatic testing covers only certain regions of that gene. As mutation analysis evolves into whole exome sequencing, coverage of germline and somatic testing will be similar if not identical. Given the increased need for somatic testing in patients with pancreatic cancer, it is possible that whole exome sequencing will replace germline testing in guidelines to come. As these “standard” tests evolve, they make the choices facing patients and providers more complex while providing hope that harnessing this knowledge will translate into substantial benefits for patients, including cancer cures and prevention.
Molecular Profiling and Its Methodology
Molecular profiling refers to the assessment of DNA, RNA, and/or proteins within an individual patient’s cancer using cells obtained from a tumor biopsy or through the capture of tumor cells circulating in the bloodstream, with the latter being less well established as a methodology. The term “molecular profiling” was initially applied to DNA analysis but evolved with advances in technology to take on a broader meaning to encompass analyses of RNA and proteins. DNA-level alterations do not necessarily lead to biological alterations, thus making examination at the “multiomic” (transcriptome and proteome) level imperative. This multipronged analysis results in the generation of an inordinate amount of data that can be processed only with the help of bioinformatic methodology. Bioinformaticians combine a host of scientific and mathematical data to create a computer infrastructure that assists in the analysis and interpretation of biological data and picks out correlations between certain gene mutations and response to a specific therapy.3 Currently used molecular profiling techniques are as follows:
DNA and RNA
- (PCR) is used to amplify and detect DNA and RNA sequences. Standard PCR involves the amplification of one or more copies of a chosen DNA sequence to produce millions of copies and enable detection and analysis. Reverse transcription PCR converts RNA templates into complementary DNA for molecular analysis.
- (ISH) localizes and determines a specific DNA or RNA sequence in a tissue section (in situ) or in circulating tumor cells using a labeled complementary DNA, RNA, or modified nucleic acid strand probe. This technique detects gene deletions, amplifications, translocations, and fusions. Gene fusions commonly occur in epithelial cancers as a result of genomic rearrangements or abnormal mRNA processing. ISH techniques include chromogenic ISH and fluorescence in situ hybridization (FISH).
- (CISH) uses brightfield microscopes for label detection.
- uses fluorescence microscopes for label detection.
- examines strands of DNA to identify mutations by analyzing long, contiguous sequencing reads. This DNA sequencing takes place according to the selective incorporation of chain-terminating dideoxynucleotides by DNA polymerase during in vitro DNA replication. This was the primary sequencing method used for well over 20 years and, although it is still widely used, next-generation sequencing (NGS) is now preferred for multigene/variant assessment.
- is a high-throughput technique that rapidly examines and more broadly detects DNA mutations (often used for circulating tumor DNA), copy number variations (CNVs), and gene fusions (using an RNA sequencing panel) across the genome. NGS can be performed on a range of cancer types using blood, solid tissue, and bone marrow samples. Precise tissue collection and workup are necessary for accurate results. Laboratory regulatory agencies constantly provide updated guidance documents pertaining to the design, development, and use of NGS-based tests, recognizing the importance of NGS in cancer diagnostics and therapeutics.
- detects and quantifies mutations, methylation, etc, through sequencing by synthesis—a method that performs DNA sequencing by detecting the nucleotide that is incorporated by DNA polymerase.
- detects changes in DNA (eg, the length of a specific DNA sequence) or RNA to indicate the presence or absence of an inserted or deleted genomic sequence.
Protein
- uses the principles of antibody binding to proteins to determine the levels of protein expression in tissue samples. Tumor-related proteins of interest can include tumor-specific antigens, protein products of oncogenes and tumor suppressor genes, tumor cell proliferation markers, and enzymes.
Molecular Profiling Assays and Why Physician Oncologists and Pathologists Should Be Familiar With Them
Modern approaches to tumor profiling assess DNA, RNA, and proteins to form a detailed molecular map to guide more precise and individualized treatment decisions. Because the field of molecular profiling is continually evolving, physician education is vital. Clinical oncologists and pathologists benefit greatly from an understanding of the technology involved, possibly even gaining hands-on experience in molecular profiling assays and their interpretation. Any treating physician should know what, when, and how to test and how to make subsequent informed, patient-personalized treatment decisions.4, 5 Correct interpretation of profiling results is critical; many fear that overinterpretation or misinterpretation will lead to treatment of patients with ineffective but expensive therapies, negatively affecting not only patient lives but also the health care budget. Laboratories offering broad molecular profiling services should be suitably Clinical Laboratory Improvement Amendments (CLIA)–certified for this exact purpose to ensure quality control (see CLIA-approved laboratories offering molecular panel analysis, below). However, even CLIA-certified laboratories do not use identical methodologies and techniques, which can still lead to variable results. Reproducibility is key, and the rationale behind assay cutoff limits should be strong. Even before a patient sample is submitted for profiling, the pathologist or the treating physician—whoever plays the lead role in any particular institution—must ensure quality-controlled tissue sample collection.6, 7 Reputable molecular testing laboratories will advise on the exact set of tumor profiling tests to perform, how to process samples, and how to interpret the final generated report, which is created to inform physicians of treatment choices for their patients. Still, physician education is key to such a critical set of processes.
Biomarker Testing in the Clinic
Targeted therapies are showing efficacy in the right subgroups of patients. Of course, these subgroups must be defined, and this process is becoming more accurate and efficient with evolving molecular testing methods and broader use in research and in the clinic. As this process improves, treatment options will improve for an increasing number of patients while eventually emerging as a more cost-effective, generally beneficial option compared with the currently accepted trial-and-error treatment model.
The biomarker information within Tables 1 through 2.12 is based mainly on the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology (NCCN Guidelines), NCCN Biomarkers Compendium (NCCN.org, Accessed February 6, 2019), and FDA recommendations and approvals (for the full definitions of all genes, please see the Supporting Information). Although the NCCN Biomarkers Compendium details not only predictive but also prognostic, diagnostic, screening, monitoring, and surveillance markers, the focus of this current review is on predictive biomarkers that can be used to guide treatment decisions. Within Tables 1 through 2.12, the classifications in the “evidence” columns are based on the level of clinical evidence available and the degree of consensus among NCCN panel and other experts. In some cases, clinical evidence comes from large, well-designed, randomized controlled trials, but in many cases, it is mostly based on data from indirect comparisons among randomized trials, phase 2 or nonrandomized trials, multiple smaller trials, retrospective studies, or merely clinical observations. In some cases, substantial clinical data are lacking and evidence comes from clinical experience alone. On the basis of all these factors and how compelling the data are, the evidence is rated as:
Table 1.
Predictive Microsatellite Instability/Mismatch Repair Testing for Any Solid Tumor
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
MMR
Expression
See in the text
IHC
dMMR and MSI-H tests on available tissue are recommended to predict response to pembrolizumaba
Lower level; wide acceptance
All
, , , or
Mutation (= dMMR expression)
NGS
Where applicable, dMMR and MSI-H tests are used together to identify whether a patient should undergo further mutation testing for Lynch syndromeb
MSI
Testing (changes in short repeated DNA sequences)
See in the text
PCR, NGS
dMMR and MSI-H tests on available tissue are recommended to predict response to pembrolizumaba
Lower level, wide acceptance
All
Where applicable, dMMR and MSI-H tests are used together to identify whether a patient should undergo further mutation testing for Lynch syndromeb
Table 2.1.
Currently Recommended Predictive Molecular Testing for NSCLC
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
ALK
Gene fusion
Metastatic workup
FISH, NGS, RT-PCRa
Response to oral ALK TKIs; alectinib has improved efficacy over crizotinib in first line
High-level, wide acceptance
Adenocarcinoma, large cell, NSCLC NOS
Fusion protein expression
IHCb
Together with testing in “never smokers” or small/mixed histology specimens
Response to oral ALK TKIs, eg, crizotinib
Lower level, wide acceptance
Squamous cell
T790M
Mutation
Metastatic workup
NGS, multiple mutation testing
Resistant to EGFR TKIs
High-level, wide acceptance
Adenocarcinoma, large cell, NSCLC NOS
exon 21 (L858R, L861), exon 20 (S768I), exon 18 (G719X, G719)
Mutation
Metastatic workup
NGS, multiple mutation testing
Sensitive to EGFR TKIs
High-level, wide acceptance
Adenocarcinoma, large cell, NSCLC NOS
Lower level, wide acceptance
Squamous cell
exon 19
Deletion
Metastatic workup
NGS, multiple mutation testing
Sensitive to EGFR TKIs
High-level, wide acceptance
Adenocarcinoma, large cell, NSCLC NOS
Lower level, wide acceptance
Squamous cell
exon 20 7p12
Insertion mutation
Metastatic workup
NGS, multiple mutation testing
Likely resistant to EGFR TKIs
High-level, wide acceptance
Adenocarcinoma, large cell, NSCLC NOS
Lower level, wide acceptance
Squamous cell
Fusion rearrangement
Metastatic workup
NGS, FISH, RT-PCR
Responsive to ROS1 TKIs
Lower level, wide acceptance
Adenocarcinoma, large cell, squamous cell, NSCLC NOS
PD-L1
Protein expression ≥50%
Metastatic workup
NGS, multiple mutation testing
Response to pembrolizumab in first-line; FDA approved treatment15
Lower level, wide acceptance
Adenocarcinoma, large cell, NSCLC, squamous cell NOS
Mutation
Metastatic workup
Gene sequencing
Resistance to EGFR TKIs. Gives poor prognosis compared with wt
Lower level, wide acceptance
All NSCLC
Mutation, V600E
Metastatic workup
NGS, pyrosequencing, AS-PCR
Emerging targeted agents19
Lower level, wide acceptance
All NSCLC
Mutation
Any time
NGS, multiple mutation testing
Emerging targeted agents20
Lower level, limited acceptance
All NSCLC
Amplification, mutation
Any time
NGS, FISH
Emerging targeted agents21
Lower level, wide acceptance
All NSCLC
Fusion, rearrangement
Any time
NGS, FISH, RT-PCR
Emerging targeted agents22, 23
Lower level, wide acceptance
All NSCLC
Table 2.2.
Currently Recommended Predictive Molecular Testing for Colon and Rectal Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
/a
Mutation
Workup for metastatic disease (suspected or proven)
NGSb
Avoid cetuximab or panitumumab treatment in patients who have tumors with and mutations (exons 2, 3, and 4 in both)
NCCN indicate , but many believe classification is
Metastatic synchronous adenocarcinoma (any T, any N, M1), suspected or documented;
Metachronous metastases by CT, MRI, and/or biopsy, documented
a
Mutation V600E
Workup for metastatic disease (suspected or proven)
NGS, pyrosequencing, AS-PCRb
Cetuximab or panitumumab treatment is not recommended in patients who have tumors with V600E mutations unless given with a BRAF inhibitor such as vemurafenib
NCCN indicates , but many believe classification is
Metastatic synchronous adenocarcinoma (any T, any N, M1), suspected or documented;
The use of irinotecan in combination with cetuximab or panitumumab plus vemurafenib is recommended in all patients with previously treated mCRC
Metachronous metastases by CT, MRI, and/or biopsy, documented
Table 2.3.
Currently Recommended Predictive Molecular Testing for Gastric, Esophageal, and Gastroesophageal Junction Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
Gene amplification
Workup any time
(F)ISH
Particularly if trastuzumab therapy is being considered
Lower level, wide acceptance
Gastric, esophageal, and gastroesophageal junction cancers
PD-L1 (CD274) and HER2 protein
Expression
Workup any time for suspected or documented, inoperable, locally advanced, recurrent, or metastatic adenocarcinoma
IHC, FISH
HER2-negative status corresponds with higher PD-L1 expression rates; together with MMR, HER2 is a potential biomarker for anti–PD-L1 therapy
Lower level, wide acceptance
Gastric, esophageal, and gastroesophageal junction cancers
Table 2.4.
Currently Recommended Predictive Molecular Testing for Pancreatic Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
and
Mutation (somatic and germline)
Initial workup if the patient has a strong family history on initial diagnosisa
NGS
A known germline mutation could help guide therapy (eg, PARP and other DDR enzyme inhibitors). In October 2018, olaparib was approved for the treatment of patients with germline -mutated, metastatic pancreatic cancer that has not progressed after first-line, platinum-based chemotherapy
Nine percent of pancreatic cancers harbor a germline or somatic or mutation, and this has an impact on response to therapy. testing in patients who are still responsive to cytotoxic therapy is becoming standard practice. The use of PARP inhibitors, specifically olaparib, in these patients is an option
Pancreatic adenocarcinoma
Table 2.5.
Currently Recommended Predictive Molecular Testing for Prostate Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
and
Mutation (somatic and germline)
Initial workup: If the patient has a strong family history on initial diagnosisa
NGS
A known germline mutation could help guide therapy (eg, PARP and other DDR enzyme inhibitors)
Lower level; wide acceptance
Prostate cancers
If the patient has metastatic, castration-resistant disease
Germline mutation
Initial workup showing strong family history
If patient has metastatic castration-resistant disease
NGS
NCCN guidelines recommend inquiring about known / mutations in a patient’s family for prostate cancer early detection6163/2 and is recommended
Lower levelb
Prostate cancers
Known / and germline mutations could help guide therapy with PARP and other DNA damage–response enzyme inhibitors
Table 2.6.
Currently Recommended Predictive Molecular Testing for Endometrial Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
ESR1 (ER)
Expression
In the stage III, IV, and recurrent disease settings
IHC
ER positivity predicts response to endocrine therapy
Lower level, wide acceptance
Uterine neoplasms, endometrial carcinoma
PMS2 (Lynch syndrome, MMR gene)
Expression
Upon diagnosis or upon recurrence if not previously tested
IHC
Loss of positivity indicates MMR, possible Lynch syndrome, and susceptibility to checkpoint inhibitors
Recommended by SGO Clinical Practice Statement
Uterine neoplasms, endometrial carcinoma
Table 2.7.
Currently Recommended Predictive Molecular Testing for Ovarian Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
and
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
,
Mutation
Recurrent disease; initial workup if the patient has a strong family history on initial diagnosis
NGS
Include other homologous recombination pathway genes and MSI or DNA MMR; helps guide therapy (eg, PARP or other DDR enzyme inhibitors; chemotherapy response)
Lower level, wide acceptance
Ovarian cancer
Table 2.8.
Currently Recommended Predictive Molecular Testing for Breast Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
ER
Expression
Noninvasive, invasive, early stage, metastatic
IHC
Predictor of response to endocrine therapy
High-level, wide acceptance
Noninvasive and invasive breast cancer, stage I-IV
PR
Expression
Invasive, early stage, metastatic
IHC
Predictor of response to endocrine therapy
High-level, wide acceptance
Invasive breast cancer, stage I-IV
Gene amplification
Invasive, early stage, metastatic
ISH
Predictor of response to HER2-targeted therapy such as trastuzumab, pertuzumab, lapatinib, or trastuzumab emtansine
High-level, wide acceptance
Invasive breast cancer, stage I-IV
HER2 (ERBB2)
Protein expression
Invasive, early stage, metastatic
IHC
Predictor of response to HER2-targeted therapy such as trastuzumab, pertuzumab, lapatinib, or trastuzumab emtansine
High-level, wide acceptance
Invasive breast cancer, stage I-IV
and
Germline mutation
Metastatica
NGS
Predictor of response to PARP inhibitor
High-level, wide acceptance
Invasive breast cancer, stage IV
Oncotype Dx
Gene expression
Hormone receptor-positive, HER2-negative
RT-PCR
Prognostic for recurrence in lymph node–negative ER-positive/HER2-negative; predictive of chemotherapy benefit in lymph node–negative ER-positive/HER2-negative
High-level, wide acceptance
Stage I, II ER-positive/PR-positive, HER2-negative
Table 2.9.
Currently Recommended Predictive Molecular Testing for Central Nervous System Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
1p19q Co-deletion75
Chromosome deletion
Preadjuvant therapy
FISH, PCR
Also prognostic and diagnostic: helps confirm the oligodendroglial character of tumors with ambiguous histologic features; the 1p19q co-deletion provides a good prognosis and predicts response to alkylating chemotherapy alone and in combination with radiation
Lower level, limited acceptance
Adult, low-grade, infiltrative, supratentorial astrocytoma/oligodendroglioma; anaplastic gliomas/glioblastoma
,
Mutation
Preadjuvant therapy glioma workup
NGS, IHC
Also prognostic and diagnostic: and mutations are related with a favorable prognosis and help in clinical trials; infiltrative gliomas that are wild-type or are likely aggressive tumors; or mutations are associated with survival benefit when treated with radiation or alkylator chemotherapy and are commonly associated with promoter methylation
Lower level, limited acceptance
Adult, low-grade, infiltrative, supratentorial astrocytoma/oligodendroglioma; anaplastic gliomas/glioblastoma
76
Promoter methylation
Preadjuvant therapy
Methylation-specific PCR, pyrosequencing
Also prognostic: strongly associated with 75 wild-type tumors; used for risk stratification in clinical trials; used in treatment decisions for elderly patients with high-grade gliomas (grades III-IV); any patient with an promoter-methylated glioblastoma obtains greater benefit from treatment with temozolomide than patients without promoter methylation
Lower level, limited acceptance
Adult, low-grade, infiltrative, supratentorial astrocytoma/oligodendroglioma; anaplastic gliomas/glioblastoma
Table 2.10.
Currently Recommended Predictive Molecular Testing for Sarcomas
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
, a
Amplification
At diagnosis
NGS
Possible clinical trial with CDK4/CDK6 inhibitor
Wide acceptancea
Well-differentiated liposarcoma, dedifferentiated liposarcoma
a
Mutation
At diagnosis
NGS
Possible trial with IDH1 inhibitor
Wide acceptancea
Chondrosarcoma
Table 2.11.
Currently Recommended Predictive Molecular Testing for Head and Neck Cancers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
PD-L1
Protein expression
Metastatic workup
IHC
Recurrent, unresectable, or metastatic (with no surgery or radiation therapy option); second-line or subsequent therapy options: pembrolizumab for PD-L1–positive disease
Lower level, wide acceptance
Cancer of the nasopharynx
Table 2.12.
Currently Recommended Molecular Testing for Melanomas: Predictive and Risk Assessment Biomarkers
BIOMARKER
TEST DETECTS
WHEN
TECHNOLOGY
RECOMMENDATIONS
EVIDENCE
CANCER TYPE
BRAF
Gene mutation, V600E
Workup any time
NGS, pyrosequencing, AS-PCR
Not recommended for patients with cutaneous melanoma who otherwise have no evidence of disease (except to guide therapy)
Lower level, wide acceptance; PREDICTIVE
Melanoma
Protein expression
IHC
Gene mutation
Workup for metastatic or recurrent disease
NGS, pyrosequencing, AS-PCR
Ascertain alterations in and from either biopsy of the metastases (preferred) or archival material if targeted therapy is under consideration
Lower level, wide acceptance; PREDICTIVE
Melanoma
Protein expression
IHC
Mutation
Workup for metastatic or recurrent disease
NGS
Ascertain alterations in and from either biopsy of the metastases (preferred) or archival material if targeted therapy is under consideration
Lower level, wide acceptance; PREDICTIVE
Melanoma
Mutation
Follow-up; risk assessment (predisposing mutation)
NGS
If the individual has personal or familial incidence of 3 or more cases of invasive melanoma or a mix of invasive melanoma, pancreatic cancer, and/or astrocytoma, consider testing with other genes that can harbor melanoma-predisposing mutations (eg, , , , and )
Lower level, wide acceptance; RISK ASSESSMENT
Melanoma
1. Based upon high-level evidence, there is uniform NCCN and other expert consensus that the intervention is appropriate (high-level, wide acceptance).
2A. Based upon lower level evidence, there is uniform NCCN and other expert consensus that the intervention is appropriate (lower level, wide acceptance).
2B. Based upon lower level evidence, there is some NCCN and other expert consensus that the intervention is appropriate (lower level, limited acceptance).
Infrequent but Important Site-Agnostic Biomarkers
Microsatellite instability-high tumors and DNA mismatch repair
Microsatellite instability (MSI) is the result of inactivation of the DNA mismatch repair (MMR) system and is characterized by a high frequency of frameshift mutations in microsatellite DNA. In a portion of tumors, MSI is caused by germline mutations in one of the MMR genes (, , , or ), which results in hereditary Lynch syndrome. However, the majority (80%) of MSI cases are sporadic, often because of hypermethylation of the gene promoter.8, 9
MSI-high (MSI-H) has been found in as many as 24 primary cancer types, most of which are displayed in Table 3,10, 11 and appears to be a generalized cancer phenotype in about 4% of all adult cancers. Tumor MSI-H status is prognostic (patients with early-stage cancers that are MSI-H have a better prognosis than those with microsatellite stable tumors) as well as predictive—many MSI-H tumors are exquisitely sensitive to PD-1/PD-L1 inhibitors.12, 13
Table 3.
Frequency of MSI-H Status Across Cancer Types
% MSI-H (NO./TOTAL NO.)
CANCER TYPE
VANDERWALDE 201810
BONNEVILLE 201711
All cancer types
3.0 (342/11,348)
3.8 (425/11,139)
NSCLC (adenocarcinoma/squamous cell carcinomab )
0.6 (12/1868)
0.5-0.6 (6/1065b )
Colorectal adenocarcinoma
5.7 (80/1395)
–
Colon adenocarcinoma
–
19.7 (85/431)
Rectal adenocarcinoma
–
5.73 (9/157)
Pancreatic adenocarcinoma
1.2 (6/518)
0.0 (0/183)
Esophageal and esophagogastric junction carcinoma
0.0 (0/189)
1.6 (3/184)
Gastric adenocarcinoma
8.7 (16/184)
19.1 (84/440)
Liver hepatocellular carcinoma
2.7 (2/73)
0.8 (3/375)
Gastrointestinal stromal tumors (GIST)
0.0 (0/52)
–
Ovarian surface epithelial carcinoma (serous cystadenocarcinomac )
1.1 (17/1517)
1.37 (6/437c )
Nonepithelial ovarian cancer
1.8 (1/56)
–
Endometrial carcinoma
17.6 (155/879)
31.4 (170/542)
Cervical cancer (squamous cell carcinoma/endocervical adenocarcinomad )
3.6 (6/168)
2.6 (8/305d )
Breast carcinoma
0.6 (6/1024)
1.5 (16/1044)
Prostatic adenocarcinoma
2.1 (4/191)
0.6 (3/498)
Bladder cancer
0.0 (0/143)
0.5 (2/412)
Glioblastoma (multiforme)
0.7 (3/427)
0.3 (1/396)
(Skin cutaneous) melanoma
0.0 (0/345)
0.6 (3/470)
Head and neck squamous carcinoma
0.0 (0/111)
0.8 (4/510)
Sarcoma
–
0.78 (2/255)
At present, the FDA has granted approval for practitioners to administer the PD-1 inhibitor pembrolizumab for the treatment of patients with unresectable or metastatic, MSI-H or MMR-deficient (dMMR) solid tumors (site-agnostic). Currently, the approval is for patients with tumors that have progressed after prior treatment who have no satisfactory alternative treatment options, as well as for patients with MSI-H or dMMR colorectal cancer (CRC) after progression on a fluoropyrimidine, oxaliplatin, and irinotecan, and in the first line for non–small cell lung cancer (NSCLC).14, 15 In 2017, the FDA granted accelerated approval of single-agent nivolumab, another PD-1 inhibitor, for the treatment of adult and pediatric patients older than 12 years with MSI-H or dMMR CRC. Subsequently, in 2018, the FDA granted accelerated approval to a combination of nivolumab plus ipilimumab (a CTLA-4 inhibitor) for treatment of the same set of patients.16, 17 See Table 1 for MSI/MMR biomarker testing recommendations.
Neurotrophic receptor tyrosine kinase
Members of the neurotrophic receptor tyrosine kinase (NTRK) fusion oncogene family, , are most prevalent in rare adult cancer types and in several pediatric cancers, although they can occur in a very small proportion (approximately 1%) of commonly occurring cancer types in adults, including NSCLCs, CRCs, head and neck cancers, thyroid cancers, bladder cancers, gliomas, and malignant melanomas (Table 418). , , and fusions and the proteins they encode (neurotrophin receptor kinase A [TRKA], TRKB, and TRKC, respectively) are observed at an increased frequency in highly aggressive cancers such as glioblastoma multiforme, and recognition of their potential oncogenic activity led to the use of this fusion family as a predictive biomarker as well as a drug target.25
Table 4.
NTRK Frequencies in Selected Cancers
NTRK GENE
TUMOR TYPE
FUSION PARTNERSa
FREQUENCY (NO./TOTAL NO.)b
, n = 7
Gliomas
, ,
0.3% (3/982)
Colorectal carcinoma
0.2% (2/1272)
Cervical carcinoma
1.5% (1/68)
Lung adenocarcinoma
0.0% (1/4073)
, n = 10
Gliomas
, , , , , (n = 2), (n = 2),
0.9% (9/982)
Lung adenocarcinoma
0.0% (1/4073)
, n = 8
Gliomas
,
0.2% (2/982)
Lung adenocarcinoma
0.0% (2/4073)
Secretory carcinoma (breast)
0.1% (1/769)
Uterine sarcoma
0.2% (1/478)
Cancer of unknown primary
0.4% (2/227)
Larotrectinib is an oral and highly selective TRK inhibitor that was granted accelerated approval by the FDA on November 26, 2018, for the treatment of adult and pediatric patients with metastatic or unresectable solid tumors that have an fusion without a known acquired resistance mutation ( kinase domain mutations, including solvent front mutations). Patients must have a cancer that has progressed after treatment and/or have no satisfactory alternative treatment for their disease.26 The approval of larotrectinib is the second tissue-agnostic FDA approval, after pembrolizumab, for the treatment of cancer.
Another TRK inhibitor named entrectinib (RXDX-101) was granted a breakthrough therapy designation by the FDA in 2017, although it has not yet been approved for use as a treatment for adult and pediatric patients who have -positive, locally advanced or metastatic solid tumors that have either progressed after prior therapies or have no acceptable standard therapy options.27, 28
fusion testing has evolved massively over the last year or 2, and new discoveries are constantly being made using a range of different assays. The fusions displayed in Table 418 are taken from a study that was originally published in 2018. Although comprehensive at the time, this table does not contain the complete list of fusions known today, in 2019. IHC has been used as an initial screening tool to inform highly sensitive but less available and more expensive molecular testing methodologies.29–31 However, it is now clear that IHC does not have sufficient sensitivity to detect all existing fusion-encoded proteins, meaning that tumor samples should certainly be assayed using FISH or NGS from the get-go.18 In conclusion, clinicians need to be aware of all 3 TRK targets and arrange adequate testing for all of them.
Germline alterations and their testing
Gene mutations can be somatic or germline; the former spontaneously occur after birth, and the latter are inherited (ie, present at birth). Tumor genetic (somatic) testing detects mutations that may actually be germline alterations, but germline alterations require confirmation in matched normal samples (eg, DNA extracted from white blood cells, buccal swabs, or cultured skin fibroblasts) from the tumor-bearing host. Suspected germline mutations and genetic testing are relevant to cancer treatment and prevention. There is potential for patients to develop tumors at other sites or for family members to develop cancer, particularly early-onset malignancies.
Table 532 lists the somatic mutations that may be germline. This table indicates the cancer types for which germline testing should be carried out if the specified somatic mutations are found in a patient’s tumor profile.
Table 5.
Best Known Somatic Mutations That Could Also Be Germline Mutations
GERMLINE OR SOMATIC MUTATION
RARE GERMLINE-ASSOCIATED SYNDROME
MAIN CANCER APPLICABILITY
Li-Fraumeni
Sarcomas, and cancers of the breast and brain
, , , ,
Lynch
Cancers of the GI tract (particularly colorectal), endometrium, ovary, brain, breast, and renal pelvis
,
Hereditary breast, ovarian, prostate, and pancreatic cancers
Cancers of the breast, ovary, prostate, and pancreas
Cowden
Cancers of the breast, endometrium, and thyroid gland
,
Familial adenomatous polyposis
Cancers of the colon and rectum, small intestine, stomach, brain, bone, and skin
Hereditary diffuse gastric cancer
Cancers of the stomach and breast
,
Familial atypical multiple mole melanoma
Melanoma, pancreatic adenocarcinoma, and cerebral astrocytoma
Werner
Pancreatic endocrine cancer and pituitary gland tumors
Retinoblastoma
Eye cancer, pinealoma, osteosarcoma, melanomas, and soft-tissue sarcomas
Multiple endocrine neoplasia type 2
Medullary thyroid cancer, and pheochromocytoma
Von Hippel-Lindau
Kidney cancers and multiple noncancerous tumors
Peutz-Jeghers
Cancers of the breast, colon and rectum, pancreas, and stomach and hamartomas
, ,
Familial paraganglioma
Paragangliomas and pheochromocytomas
Birt-Hoge-Dube
Chromophobe renal cell cancers
,
Tuberous sclerosis
Angiofibromas, angiomyolipomas, giant cell astrocytomas
Neurofibromatosis type 1
Optic gliomas and neurofibromas
Neurofibromatosis type 2
Schwannomas, meningiomas, gliomas, neurofibromas
Gorlin
Childhood primitive neuroectodermal tumors, skin basal cell carcinomas
,
Juvenile polyposis
Multiple noncancerous growths in the colon
There are 3 main categories of tumor genetic modifications with wide variation in the expectation that these reflect germline changes. The first comprises common tumor mutations associated with rare germline alterations. For example, mutations in are found in greater than 60% of lung cancers.33 Although mutations can be inherited in the Li-Fraumeni syndrome, such familial syndromes are rare. It is believed for the most part that there is little need for germline testing unless the personal or family history is suggestive of such a syndrome. The second category comprises moderately common somatic mutations that may be associated with familial syndromes. For example, in colon cancer, dMMR is found by routine MSI or IHC testing in about 12% of tumors.34 Molecular germline testing demonstrates that about one-quarter of these dMMR alterations are inherited. Hence tumor testing should lead to germline confirmation in patients and possibly further evaluation of family members. The final category comprises uncommon tumor mutations that often reflect germline mutations. As an example, patients with breast and ovarian cancers regularly have germline testing done for and , especially if the personal or family history is suggestive. With routine molecular genetic tumor testing, / mutations are being found in patients with other tumors where it is less expected. An analysis of 100 patients with pancreatic cancer found that 7 had mutations in , 4 of which were in the germline.35 Finding mutations in the tumor may aid in choosing therapy but requires germline testing for confirmation and consideration of genetic counseling for the family.
It has generally been considered that germline testing is not always needed if somatic tumor testing has been done. However, it must be kept in mind that molecular genetic tumor testing can miss a small percentage of inherited cases, where mutations are outside the hotspots covered in the somatic panel or large-scale deletions and duplications have occurred. Conversely, larger gene panel profiling may actually identify previously unknown, clinically relevant alterations that are germline, either de novo or inherited from parents, despite a lack of associated clinical history.36
In conclusion, taking into consideration the increasing availability of germline testing and whole exome sequencing to identify inheritable mutations, as well as the personal and family history of cancer and the potential need for genetic counseling, medical teams can help provide better treatment selection for patients with some types of cancer and help to create a systematic approach to hereditary risk.
Disease-Specific Biomarkers
In the subsections below and in Tables 2.1 through 2.12, we address the currently accepted genes or gene products that act as predictive biomarkers (and risk assessment markers in some cases) for each specific solid tumor. Details on when in the disease course the presence or levels of these markers should be assessed are also included. Under each of the following subsections, we also include some description of pertinent biomarkers in research. Compelling evidence suggests that these biomarkers will be listed in the NCCN “recommended” biomarker category in the foreseeable future.
Lung cancers
Lung cancer therapy continues to follow the genomic testing paradigm (see Table 2.115, 19–24). All patients with NSCLC should be tested for , , , , and PD-L1 at baseline before treatment. Patients with uncommon mutations of may also be treated with tyrosine kinase inhibitor therapy. Other recommended markers of interest include insertion 20 mutations, rearrangements, and exon 14 mutations. All of these targets are still being actively investigated in clinical studies and hold potential for patient treatment.
Gastrointestinal cancers
Colon and rectal cancers
Oncologists now recommend the assessment of several predictive markers in patients with CRCs (see Table 2.2). The ideal time to perform genomic testing for treatment purposes is a matter of some controversy and varies depending on disease stage. At the time of initial diagnosis of a stage I, II, or III tumor, it is reasonable to perform MSI testing. Patients with MSI-H, locally confined tumors have a better prognosis, and recommendations are for patients with MSI-H stage II tumors to forgo adjuvant therapy.37, 38 Additional evidence suggests that 5-fluorouracil (5-FU) and related agents, such as capecitabine, can actually worsen outcomes when delivered as single agents to patients with early-stage MSI-H CRCs.39, 40 Treatment with an oxaliplatin regimen is the standard of care recommended for MSI-H stage III CRCs. Finally, guidelines now recommend universal MSI testing in all stages of CRC to determine whether patients have a germline mutation indicative of Lynch syndrome.41 If both the tumor DNA and the patient’s germline DNA harbor an MMR defect, this indicates that the patient has Lynch syndrome. Oncologists need to refer these patients for genetic counseling and a discussion about potential testing of relatives. Such individuals should have screening for Lynch syndrome–associated cancers at an earlier age, and more intensive screening is called for than is recommended for individuals without such a cancer susceptibility mutation. There is additional evidence that the use of aspirin can reduce premalignant polyp formation in patients and their relatives with MSI-H tumors.43 Aspirin has also been associated with improved outcomes in patients with tumors that harbor mutations, suggesting a potential value for assessment of mutations in that gene.44 MSI testing is also an eligibility requirement for the current US intergroup trial of combined 5-FU, leucovorin, and oxaliplatin (FOLFOX) with or without atezolizumab, a PD-1 inhibitor, in patients with MSI-H stage III colon cancer.
In patients with advanced CRC, MSI testing is also indicated at diagnosis. Mutations in or overexpression of additional genes that are predictive of outcomes include and . Often, other than for mutations, the optimal time for this testing is when tumors become refractory to standard chemotherapy so that the assessment reflects the current status of the disease. Patients with MSI-H tumors are now eligible for therapy with PD-1–targeting, PD-L1–targeting, and/or CTLA-4–targeting immunotherapies after their disease becomes refractory to standard chemotherapy. Those with fusions are candidates for treatment with larotrectinib.26 Individuals whose tumors harbor a mutation are insensitive to treatment with and should not receive an anti-EGFR–targeted monoclonal antibody such as cetuximab or panitumumab.45 It is likely that additional genomic analyses that are currently underway or to be evaluated in future studies, involving whole genome or whole exome sequencing in cohorts of patients with known outcomes, will identify other mutations that have either prognostic or predictive utility.
as a CRC prognostic factor
mutational status is used as a strong predictor for overall survival (OS) at all stages of disease; patients with -mutated CRC have a generally poor prognosis.46–52 V600E is the best known mutation assessed using NGS.53 Compared with patients who have CRC with wild-type tumors, patients whose tumors manifest a mutation are generally older and more likely to be female. Such patients commonly have higher grade cancers at diagnosis, with a primary tumor that is more likely to be right-sided and to have a higher number of cancer-involved lymph nodes. These -mutated tumors are also more likely to be MSI-H.54
Gastric, esophageal, and gastroesophageal junction cancers
See Table 2.3.42
Pancreatic cancers
See Table 2.4.
Genitourinary cancers
Bladder cancers
In The Cancer Genome Atlas extended 2017 study carried out by Robertson et al, findings from the complete cohort of 412 muscle-invasive bladder cancer cases revealed that mutations in the DNA repair genes (n = 57; 14%) and (n = 40; 10%), and deletions in (n = 10; 2%) were significant.55
It was found that all nonsilent somatic mutations were missense, and many could be mapped within the conserved helicase domain. Dominant negative effects on ERCC2 function were observed.56 Thus, bladder cancer missense mutations in were associated with improved response to cisplatin-based chemotherapy. However, mutations are distributed across the gene, and the functional impact of most individual mutations is unknown. Recently, Li et al reported developing a microscopy-based assay that measures the nucleotide excision repair function of clinically observed mutations. Most helicase domain mutations impaired the function. In addition, a preclinical -deficient bladder cancer model showed that loss was sufficient to drive cisplatin sensitivity. Thus, was concluded to be a predictive biomarker in bladder cancer. Moreover, this study underscores the importance of combining genomic and functional approaches in a co-clinical trial to guide precision oncology for conventional chemotherapy agents. Current evidence presented here supports the idea that and are potentially useful markers in muscle-invasive bladder cancer.55–57
Prostate cancers
It was recently reported that patients with metastatic castration-resistant prostate cancer (mCRPC) harboring germline mutations in and have superior clinical outcomes after first-line treatment with abiraterone and enzalutamide (see Table 2.5).58 The authors suggested that this improved response is likely driven by mutations in , , and . Because these conclusions were based on only 9 patients harboring germline mutations and the study was not entirely prospective, these findings require prospective validation in larger patient cohorts. A separate, small, retrospective study found that all responders to poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitor therapy harbored mutations, whereas nonresponders did not.59 However, it was agreed that the functional relevance of mutations in DNA repair genes other than should be considered before committing to PARP inhibitor therapy.
At the American Society of Clinical Oncology 2018 meeting, De Bono et al60 reported preliminary findings from the KEYNOTE-199 phase 2 trial comparing responses to the immune checkpoint inhibitor pembrolizumab in patients who had mCRPC with or without tumor expression of PD-L1. Thus, pembrolizumab showed antitumor activity and disease control with acceptable safety in patients with docetaxel-refractory mCRPC, regardless of PD-L1 status. Of note, the response rate was numerically higher in patients with somatic or mutations (12%), indicating that these could be predictive markers of response to checkpoint inhibitors. It can be seen from Table 2.561 that testing of is NCCN recommended. Testing of is also suggested but not yet NCCN recommended.
Gynecologic cancers
Endometrial cancers
As noted above (see Microsatellite instability high tumors and DNA mismatch repair), the presence or absence of MSI should be determined through universal tumor molecular testing in every patient with uterine cancer (see Table 2.6).62 Approximately 2% to 5% of uterine cancers are because of Lynch syndrome, caused by germline mutations in , , , or . Abnormalities in should prompt hypermethylation testing, as this can also cause tumors to be MSI-H in the absence of a germline mutation. The detection of a germline mutation affects subsequent screening for colon and ovarian cancer and prompts cascade testing to identify other affected family members. The presence of MSI-H because of either a germline mutation or hypermethylation provides an indication for pembrolizumab in the setting of recurrent uterine cancer, based on site-agnostic FDA approval granted in 2017.13 Women with -aberrant endometrial cancers demonstrate a favorable prognosis and may require less aggressive therapy, although this remains theoretical at present. Identification of hotspot mutations in genes such as , , , and may correlate with biological behavior but are not yet targetable. Phase 2 data demonstrate activity of mTOR inhibitors in endometrioid carcinoma of the uterus, but these trials were not assay-directed to determine whether molecular testing can select for potential activity.64
Ovarian cancers
The presence of pathogenic mutations in -related genes identify an important subset of high-grade serous epithelial ovarian cancers that have a specific biology, natural history, and susceptibility to platinum and PARP inhibitors. The spectrum of mutations in this category includes those in , , , , , , , , , , , and (see Table 2.7).65–67 Patients with these mutations have an improved prognosis with a higher likelihood of platinum sensitivity and long-term survival. Homologous recombination (HR)–deficient (HRD) tumors act similarly to tumors that have -related mutations and may serve as a surrogate for platinum sensitivity. Identification of these mutations directly affects therapy, as patients should be considered for treatment with PARP inhibitors immediately after upfront therapy with platinum and a taxane, based on the improved progression-free survival (PFS) observed in the SOLO-1 trial (Olaparib Maintenance Monotherapy in Patients With BRCA Mutated Ovarian Cancer Following First Line Platinum Based Chemotherapy; ClinicalTrials.gov identifier NCT01844986).68 This international superiority trial showed a 70% reduction in risk of ovarian cancer progression in women with germline or somatic mutations who received maintenance olaparib after primary therapy with paclitaxel and carboplatin. Conversely, patients without -related mutations may be better served by antiangiogenic therapy with bevacizumab concurrent with upfront platinum and taxane therapy followed by maintenance bevacizumab therapy (Gynecologic Oncology Group study 0218 [GOG-7]).69, 70
In the recurrent setting, PARP inhibitors (olaparib and rucaparib) as monotherapy were first approved for ovarian cancer patients with mutations or HRD. This indication has now been expanded to include olaparib, rucaparib, and niraparib as switch maintenance therapy for patients with platinum-sensitive ovarian cancer who have responded to platinum in the second-line or third-line setting.65–67, 71
The identification of -related gene mutations is also necessary to perform cascade testing on family members to identify affected family members who may be candidates for risk-reducing surgery and surveillance to prevent subsequent ovarian, tubal, peritoneal, and breast cancer.
Evaluation of PD-1 and PD-L1 status is useful in patients with ovarian cancer because pembrolizumab is approved for patients with MSI-H tumors based on a site-agnostic label. Single-agent activity for PD-1 inhibitors has been limited in patients with ovarian cancer, but checkpoint inhibitors are under study in the JAVELIN trials. The combination of PARP inhibitors with checkpoint inhibitors has been investigated, and initial response rates of 25% to 30% have been noted. The larger ATHENA trial (A Study in Ovarian Cancer Patients Evaluating Rucaparib and Nivolumab as Maintenance Treatment Following Response to Front-Line Platinum-Based Chemotherapy; ClinicalTrials.gov identifier NCT03522246) of maintenance rucaparib and nivolumab therapy is currently accruing patients with ovarian cancer who have responded to front-line, platinum-based chemotherapy.
Although initial trial results using MEK inhibitors in the treatment of patients with low-grade serous carcinomas have been disappointing, multiple studies are ongoing investigating MEK inhibitor monotherapy and combination therapy. Other rare ovarian cancers have different molecular profiles, but targeted therapies remain largely unstudied.
Cervical cancers
The treatment of patients with recurrent cervical cancer has been problematic, and their prognosis is dismal. Bevacizumab was approved for recurrent disease in combination with platinums, taxanes, and topotecan; however, no molecular markers have yet been found that can predict patient treatment response. Pembrolizumab was FDA-approved in 2018 for patients with recurrent and metastatic cervical cancer who had disease progression on or after chemotherapy and whose tumors expressed PD-L1, based on a 14% objective response rate seen in KEYNOTE 158 (Study of Pembrolizumab [MK-3475] in Participants With Advanced Solid Tumors; ClinicalTrials.gov identifier NCT02628067). Promising data also exist for single-agent nivolumab, which demonstrates a 26% response rate in the recurrent setting (ClinicalTrials.gov identifier NCT02488759). Trials evaluating combination therapy with nivolumab and ipilimumab are currently underway.
Breast cancers
The well-established biomarkers that drive treatment decisions for patients with breast cancers are estrogen receptor (ER) expression, progesterone receptor (PR) expression, and human epidermal growth factor receptor-2 (HER2) overexpression or amplification in the tumor (see Table 2.8). Determination of ER, PR, and HER2 status is recommended for all newly diagnosed invasive breast cancers and for any recurrences when feasible. These are routinely used to predict response to therapy and guide treatment planning for patients with breast cancer.
Some new markers that show promise for future use in breast cancer are the androgen receptor (AR), , and PD-L1. Overexpression of AR occurs in a subset of triple-negative breast cancers (TNBC).72 Clinical trials of AR-targeted treatments have shown promising preliminary results in patients with metastatic, AR-positive TNBC.73 Mutations in occur in the ligand-binding domain of the ER and can lead to a ligand-independent, constitutively active form of the ER. This is a potential mechanism of resistance to aromatase inhibitors. De novo mutations have been most commonly detected during or after treatment with aromatase inhibitors for hormone receptor-positive breast cancer.74 The treatment implication is to consider using selective ER downregulators that target ER directly in the setting of an mutation. The role of PD-L1 as a predictive biomarker for the treatment of patients with breast cancer using checkpoint inhibitors will be further delineated with several maturing trials evaluating immune checkpoint blockade in the treatment of breast cancer. In addition, multiparameter genomic assays, such as Oncotype DX (Table 2.8), MammaPrint, and Prosigna (formerly called PAM 50), are being used routinely for decision making in early-stage breast cancer. MammaPrint and Prosigna are prognostic for recurrence of tumors that are lymph node negative, have 1 to 3 positive lymph nodes, or are ER-positive but HER2-negative. Additional multigene assays used for consideration of adjuvant therapy in patients with breast cancer are EndoPredict and the Breast Cancer Index.
Central nervous system cancers
Although broad panels are often appropriate and especially meaningful in the metastatic setting when conventional therapy has failed, more limited panels may be a consideration (see Table 2.975, 76). This can be exemplified by central nervous system tumors, in which genetic alterations are not just prognostic or predictive, but diagnostic. Before 2016, the World Health Organization (WHO) classification relied strictly on histologic features to differentiate tumors of astrocytic and oligodendroglial lineage.77 Although patients have significantly different treatment paradigms and survival depending on which of these tumor lineages they harbor,78 occasionally features from both lineages can be found within the same tumor, resulting in a diagnosis of a “hybrid” oligoastrocytoma. This is further compounded by high interobserver discordance; thus, some institutions diagnose this entity more frequently than others.79 By combining both genotype and classical histologic findings, it is now possible to diagnose nearly all of these tumors to be compatible with either oligodendroglioma or astrocytoma. This has resulted in modifications to the WHO classification in 2016 to include both histologic phenotype and molecular genotype with consideration of mutation, 1p19q codeletion, loss, and mutation when diagnosing gliomas.75 Furthermore, epigenetic silencing of the promoter of the methyl-guanine methyl transferase gene by gene promoter methylation is frequently tested because it is highly prognostic and also predictive, correlating with a response to or benefit of alkylating agent chemotherapy.76
It has been found that most glioblastomas have potential actionable genomic alterations.80, 81 A recent NGS analysis using a 315-gene panel found that, of 43 patients, 95% had at least 1 therapeutically actionable genomic alteration of a median of 4.5 genomic alterations per patient. The most common genomic alteration detected was in (40%). Genotype-directed treatments were prescribed in 13 patients, representing a 30% treatment decision impact. Treatment with targeted agents—including everolimus as a single agent and in combination with erlotinib, afatinib, palbociclib, trametinib, and BGJ398—elicited no response.82
A fusion between Brevican () and is a potent oncogenic driver of high-grade gliomas and confers sensitivity to entrectinib.83 A case report of a – fusion in glioneuronal tumors highlights its clinical importance as a novel, targetable alteration,84 and an open-label, multicenter, global phase 2 basket study of entrectinib for the treatment of patients with locally advanced or metastatic solid tumors that harbor , , or rearrangements (ClinicalTrials.gov identifier NCT02568267) is currently recruiting glioma patients.
For pediatric low-grade gliomas, V600E is a potentially highly targetable tumor mutation, which was detected in 17% of patients who exhibited poor outcome on receipt of chemotherapy treatment.85 In a recent evaluation of dabrafenib in a phase 1/2 trial that included 32 children with relapsed or refractory, low-grade gliomas, findings of an objective response rate of 38% and stable disease in another 44% of patients are extremely exciting. It is encouraging that these drugs could be effective agents that allow us to replace chemotherapy entirely for pediatric glioma.86
Other central nervous system types for which molecular profiling has a role include ependymoma ( fusion), diffuse midline cerebellar gliomas (histone 3 mutations), medulloblastoma ( vs activated), and ependymoma ( amplification). Although many of these tumors inevitably recur and a broader panel may be useful at some point in the course of the disease to define clinical trial options, obtaining a limited panel that contains the molecular alterations considered within the WHO criteria remains a reasonable option.
We certainly see the potential implication of molecular profiling for a routine part of therapeutic decision making beyond classification and prognostic prediction for patients with glioma. Of other mutations tested, the epidermal growth factor gene variant vIII encodes a promising molecular target. amplification could be useful in the treatment of glioblastomas. However, agents targeting EGFR signaling pathways have displayed limited or no therapeutic efficacy in glioblastoma clinical trials. ABT-414 (an investigational, anti-EGFR monoclonal antibody drug conjugate) alone87 or in combination with temozolomide showed a trend toward improved survival and was safely administered with radiation therapy.88, 89
The V600E mutation, which is analyzed using NGS, is predictive and prognostic for low-grade pediatric glioma. This mutation is frequently found in gangliogliomas and in about two-thirds of grade II xanthroastrocytomas. It is assumed that this alteration constitutively activates the RAS/RAK/MEK/ERK kinase pathway. When BRAF kinase inhibitor treatment effects are validated within low-grade glioma, the drug could transform the V600E mutation from a diagnostic marker to predictive marker of response to therapy.90
Sarcomas
Sarcomas are heterogeneous cancers comprising over 50 diverse histological subtypes (see Table 2.10). As a group, they have a low occurrence incidence and are considered rare cancers. Although there is some crossover, pediatric and adult sarcomas have distinctly different histologies as well as different genetic drivers. The majority of genomic variations (translocations, CNVs, complex karyotypes, etc) provide important predictive diagnostic information rather than potential therapeutic targets. Thus, (for Ewing sarcoma), (alveolar rhabdomyosarcoma), (monophasic synovial sarcoma), (biphasic synovial sarcoma), and (myxoid liposarcoma) fusions are diagnostic markers that should be tested at initial workup using RNA sequencing techniques, particularly FISH. There are several prominent exceptions to this diagnosis-only rule in gastrointestinal (GI) stromal tumors, in which mutations in (particularly exon 11) and are notable biomarkers for therapeutic intervention with the tyrosine kinase inhibitors imatinib and sunitinib.
Head and neck cancers
PD-1 is highly expressed in head and neck squamous cell carcinomas (HNSCCs) and, in 2016, the PD-1 inhibitors nivolumab91 and pembrolizumab92 were both approved for the treatment of HNSCC that has metastasized or recurred on or after treatment with platinum chemotherapy (see Table 2.11). PD-L1 testing is now recommended in patients undergoing workup for metastatic HNSCC, with the intention of offering pembrolizumab as a treatment option to those with PD-L1–positive tumors.
is reportedly overexpressed in between 90% and 100% of HNSCCs.93 Accordingly, cetuximab is an approved targeted therapy for this disease and is usually administered regardless of mutation testing. HNSCCs can develop resistance to cetuximab. Activation of other EGFR family members (HER2, HER3) can play a role in this resistance, as can c-MET, insulin growth factor receptor (IGFR), and PI3K.94 is frequently mutated in HNSCC and plays a key role in the progression of HNSCC.95, 96 Targeted agents against all these markers have been developed and have undergone or are undergoing various phases of clinical testing. Human papillomavirus (HPV)-related HNSCCs are increasing in incidence and have different oncogenic processes compared with HPV-unrelated HNSCCs. Patients with HPV-positive HNSCCs respond better to treatment and have a better prognosis than their HPV-negative counterparts. Therefore, for the sake of disease diagnosis, treatment, and management, it is useful to accurately discriminate between the HPV-positive and HPV-negative HNSCCs, which can be done through tumor P16 testing by IHC; thus, P16 positivity corresponds to HPV positivity.97
Melanomas
To date, the only FDA-approved predictive biomarker in patients with advanced melanoma is genotyping (see Table 2.12). Approximately one-half of melanomas that originate from cutaneous primary sites will harbor a V600 mutation.98 This leads to constitutive activation of the MAPK pathway and increased cell proliferation, metastasis, and survival mechanisms. Vemurafenib, dabrafenib, and encorafenib are BRAF-targeted therapies that preferentially inhibit cells harboring the V600 mutation. It is important to be aware that selective inhibitors of BRAF encoded by mutant V600 can cause paradoxical activation of the MAPK pathway in cells that are V600 wild-type (particularly if they harbor a mutation). This effect occurs through RAF dimerization, leading to increased cell proliferation rather than inhibition.99 The combination of selective BRAF inhibitors with MEK1/MEK2 inhibitors is now FDA approved only for patients with V600-mutant melanoma. In patients with resected, stage III, V600E/V600K–mutant melanoma, dabrafenib plus trametinib improves relapse-free survival by 53%.100 Similarly, dabrafenib plus trametinib and other BRAF/MEK inhibitor combinations have demonstrated objective response rates of up to 68% in patients with unresectable advanced V600E/K mutant melanoma.101
Other oncogenic driver mutations have been identified in melanomas for which targeted therapies have demonstrated clinical activity. mutations (and amplifications) have been identified in up to 20% of patients with advanced melanoma, particular those with chronic sun-damaged, acral, or mucosal melanoma subtypes.102, 103 Of note, mutations are often seen across multiple exons, and hotspot mutations are not typically observed. This patient population has a reported response rate to imatinib of 21% to 29%.104–106 Higher response rates were seen in individuals whose melanoma harbored exon 11 and 13 mutations. Another important oncogene, , is mutated in approximately 20% of melanomas—most commonly at the Q61 position.107 Direct targeting of NRAS has proven difficult, but clinical activity has been demonstrated by targeting the downstream MAPK pathway with MEK1/MEK2 inhibitors. The MEK inhibitor binimetinib showed superior clinical outcomes compared with dacarbazine.108 However, the objective response rate of binimetinib was only 15%, and this agent has not yet been approved by the FDA for this indication.
With regard to predictive biomarkers for immune checkpoint therapies in melanoma, several have shown enrichment for greater clinical activity, mostly in post hoc or retrospective analyses, but have not been approved by the FDA for routine clinical use.109 These include positive PD-L1 IHC, immune gene expression profiles, and high tumor mutational burden (TMB) (see The role of TMB—an emerging biomarker, below) by targeted exome sequencing. For example, response rates to anti-PD-1/PD-L1 therapy were 81%, 36%, and 10% for patients whose tumors had >23.1 mutations per megabase (MB), 3.3 to 23.1 mutations per MB, and <3.3 mutations per MB, respectively.110 However, patients with low or negative biomarkers can still benefit from immune checkpoint therapies, and some studies have shown marginal differences between groups. The PD-L1 IHC analyses from the Checkmate 067 study demonstrate this concept well: response rates were 43% and 58% with nivolumab monotherapy in patients whose tumors had <5% PD-L1 staining versus >5% PD-L1 staining, respectively.111 Biomarkers may be useful in the application of nivolumab/ipilimumab combination therapy over nivolumab monotherapy for patients with melanoma based on Checkmate 067 study data. Improvement in PFS with the combination approach was best seen in patients whose tumors harbored a V600 mutation or had <1% PD-L1 staining (hazard ratios, 0.62 and 0.68, respectively).
The Gray Area Between Research and Clinical Practice
Core clinical markers in current use by expert molecular profiling laboratories, the frequencies of these markers in a range of tumor lineages, and assay types used for their assessment can be found in Table 6 (Caris Molecular Intelligence). Many of the markers and their assays in Table 6 are essentially still classified as belonging in a “research” category, and the NCCN has not yet recommended universal testing for these genes. Nevertheless, they have been reported as actionable and useful by a general consensus of experts in the research community. Because the use of broader gene panels and full-scale NGS is still in the gray area between research and clinical practice, it comes burdened with benefit-to-cost ratio controversies. The field is also evolving rapidly, with fluidity existing in the classification of genes as clearly, possibly, or unlikely to be relevant to treatment considerations.
Table 6.
Caris Molecular Intelligence Core Clinical Marker Frequencies for Tumor Lineages
NSCLC
ANAL CANCER
COLORECTAL CANCER
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
MSI
NGS
10
1893
0.5
TML
NGS
6
91
33.0
NGS
1744
3427
50.9
TML
NGS
712
4557
15.6
PD-L1
IHC
63
191
33.0
NGS
146
3427
4.3
PD-L1 (22c3)
IHC
2541
5658
44.9
NGS
22
92
33.0
NGS
285
3427
8.3
ALK
IHC
10
4606
0.2
NGS
10
92
33.0
NGS
600
3427
17.5
NGS
84
4606
1.8
MSI
NGS
0
40
0.0
NGS
14
3424
0.4
CNV
84
4606
1.8
PERITONEAL CANCER
Fusion
32
1272
2.5
Fusion
84
4606
1.8
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
MLH1
IHC
5840
6132
95.2
ISH/fusion
10
4606
0.2
NGS
42
87
48.3
PMS2
IHC
5719
6097
93.8
NGS
10
4606
0.2
NGS
24
87
27.6
MSH2
IHC
6011
6121
98.2
Fusion
19
4164
0.5
NGS
10
87
11.5
MSH6
IHC
5947
6104
97.4
Fusion
14
4186
0.3
NGS
2
87
2.3
MSI
NGS
83
1346
6.2
Fusion
19
4164
0.5
NGS
4
87
4.6
TML
NGS
247
3400
7.3
PTEN
IHC
7792
12,618
61.8
NGS
1
87
1.1
HER2
IHC
161
8708
1.8
NGS
165
4606
3.6
NGS
3
87
3.4
CISH
129
4460
2.9
(L858R)
NGS
174
4659
3.7
MLH1
IHC
190
192
99.0
PD-L1
IHC
196
6405
3.1
(exon 19 del)
NGS
260
4659
5.6
PMS2
IHC
189
192
98.4
PTEN
IHC
5334
11,407
46.8
T790M
NGS
62
4773
1.3
MSH2
IHC
189
192
98.4
SMALL BOWEL CANCER
tertiary
NGS
3
4659
0.1
MSH6
IHC
187
192
97.4
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
NGS
70
4606
1.5
MSI
NGS
1
27
3.7
NGS
100
183
54.6
NGS
1319
4606
28.6
TML
NGS
1
87
1.1
NGS
3
183
1.6
Fusion
3
3797
0.1
PD-L1 (SP142)
IHC
7
211
3.3
NGS
14
183
7.7
NTRK
IHC
35
2031
1.7
PTEN
IHC
252
393
64.1
NGS
26
183
14.2
NGS
219
4606
4.8
NGS
1
183
0.5
NGS
0
4606
0.0
MLH1
IHC
88
96
91.7
NGS
9
4761
0.2
MSH2
IHC
90
96
93.8
SMALL CELL LUNG CANCER
MSH6
IHC
89
96
92.7
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
PMS2
IHC
89
96
92.7
MSI
NGS
0
88
0.0
MSI
NGS
10
71
14.1
TML
NGS
13
205
6.3
TML
NGS
18
182
9.9
PD-L1
IHC
182
206
88.3
HER2
IHC
10
482
2.1
NGS
99
205
48.3
CISH
11
269
4.1
NGS
11
206
5.3
PD-L1
IHC
25
342
7.3
NGS
0
206
0.0
PTEN
IHC
264
526
50.2
NGS
0
206
0.0
Fusion
6
57
10.5
NGS
0
49
0.0
GASTROESOPHAGEAL CANCER
CHOLANGIOCARCINOMA
BLADDER CANCER
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
NGS
31
922
3.4
NGS
39
474
8.2
MSI
NGS
4
152
2.6
NGS
5
921
0.5
NGS
14
474
3.0
TML
NGS
58
361
16.1
NGS
50
921
5.4
NGS
35
474
7.4
NGS
21
364
5.8
NGS
6
922
0.7
NGS
23
474
4.9
NGS
12
364
3.3
NGS
3
921
0.3
NGS
82
474
17.3
NGS
17
364
4.7
NGS
15
921
1.6
NGS
16
474
3.4
NGS
0
364
0.0
NGS
2
921
0.2
NGS
13
474
2.7
NGS
0
364
0.0
NGS
44
921
4.8
NGS
30
474
6.3
NGS
43
364
11.8
NGS
7
921
0.8
MLH1
IHC
70
73
95.9
NGS
55
364
15.1
NGS
686
922
74.4
PMS2
IHC
69
73
94.5
NGS
23
364
6.3
NGS
30
922
3.3
MSH2
IHC
72
73
98.6
PD-L1
IHC
162
788
20.6
NGS
58
922
6.3
MSH6
IHC
72
73
98.6
PROSTATE CANCER
NGS
17
921
1.8
MSI
NGS
1
177
0.6
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
PD-L1
IHC
180
1804
10.0
TML
NGS
15
469
3.2
MSI
NGS
6
151
4.0
MSI
NGS
15
389
3.9
HER2/
IHC
40
1301
3.1
TML
NGS
15
416
3.6
TML
NGS
47
916
5.1
CISH
38
618
6.1
NGS
22
422
5.2
HER2
IHC
75
1431
5.2
PD-L1
IHC
78
934
8.4
NGS
6
365
1.6
CISH
168
1323
12.7
Fusion
2
131
0.0
NGS
26
365
7.1
NGS
34
462
7.4
Fusion
1
149
0.7
NGS
35
440
8.0
NGS
78
922
8.5
Fusion
7
149
4.7
PD-L1
IHC
25
811
3.1
PANCREATIC CANCER
HEPATOCELLULAR CARCINOMA
AR
IHC
1127
1213
92.9
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
Fusion
57
198
28.8
MSI
NGS
6
456
1.3
NGS
53
166
31.9
TML
NGS
18
1149
1.6
NGS
56
166
33.7
NGS
942
1164
80.9
NGS
8
166
4.8
NGS
2
1164
0.2
MSI
NGS
1
69
1.4
NGS
18
1164
1.5
TML
NGS
4
166
2.4
NGS
229
1164
19.7
PD-L1
IHC
26
366
7.1
HER2
IHC
38
2096
1.8
ISH
26
4063
0.6
PD-L1
IHC
222
2682
8.3
NGS
42
1164
3.6
NGS
13
1031
1.3
NGS
36
1031
3.5
RENAL CANCER
ENDOMETRIAL CANCER
BREAST CANCER (CONTINUED)
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
MSI
NGS
1
107
0.9
TML
NGS
282
1469
19.2
NGS
59
1960
3.0
TML
NGS
3
327
0.9
MSI
NGS
163
796
20.5
NGS
88
1960
4.5
NGS
33
333
9.9
MSI
Frag analysis
267
1831
14.6
NGS
160
2164
7.4
NGS
2
332
0.6
NGS
42
1841
2.3
NGS
32
2169
1.5
NGS
1
332
0.3
NGS
1137
1843
61.7
NGS
159
2164
7.3
NGS
6
333
1.8
NGS
823
1843
44.7
NGS
3
2164
0.1
NGS
60
332
18.1
NGS
745
1841
40.5
NGS
4
2164
0.2
NGS
0
332
0.0
NGS
21
1843
1.1
NGS
86
2169
4
NGS
46
332
13.9
CNV
61
1867
3.3
NGS
27
2164
1.2
NGS
5
332
1.5
MSH6
IHC
2273
2295
99
NGS
143
2169
6.6
NGS
2
332
0.6
MSH2
IHC
2301
2306
99.8
NGS
15
2164
0.7
NGS
153
333
45.9
PMS2*
IHC
1887
2293
82.3
NGS
1203
2169
55.5
PD-L1
IHC
117
630
18.6
MLH1*
IHC
1912
2298
83.2
GLIOBLASTOMA
OVARIAN CANCER
PD-L1
IHC
460
4502
10.2
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
CERVICAL CANCER
NGS
161
851
18.9
MSI
NGS
23
1484
1.5
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
NGS
3
851
0.4
TML
NGS
63
3434
1.8
MSI
NGS
2
116
1.7
NGS
17
851
2.0
NGS
238
2924
8.1
TML
NGS
20
305
6.6
MSI
NGS
1
265
0.4
NGS
180
2922
6.2
NGS
56
307
18.2
TML
NGS
28
847
3.3
NGS
63
3463
1.8
NGS
92
307
30.0
NGS
59
851
6.9
NGS
290
3463
8.4
PD-L1
IHC
191
802
23.8
NGS
18
851
2.1
NGS
158
3463
4.6
BREAST CANCER
NGS
8
851
0.9
NGS
253
3463
7.3
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
Methylation
828
1773
46.7
NGS
170
3463
4.9
MSI
NGS
5
779
0.6
1p19q
FISH
52
779
6.7
NGS
279
3458
8.1
TML
NGS
76
2146
3.5.0
vIII
Fusion
87
630
13.8
NGS
19
3452
0.6
PD-L1
IHC
389
5519
7
CNV
257
828
31
ER
IHC
7947
16,384
48.5
AR
IHC
5698
11,114
51.3
PD-L1
IHC
209
1346
15.5
PR
IHC
4698
16,353
28.7
ER
IHC
5598
9404
59.5
Fusion
8
404
2.0
PD-L1
IHC
748
8693
8.6
PR
IHC
3806
9362
40.7
Fusion
11
404
2.7
HER2
IHC
900
9299
9.7
Fusion
3
404
0.7
CISH
726
6087
11.9
Fusion
12
404
3.0
NGS
50
2169
2.3
Fusion
2
404
0.5
Fusion
1
404
0.2
SARCOMA
MELANOMA
UVEAL MELANOMA
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
MSI
NGS
6
350
1.7
MSI
NGS
0
293
0.0
MSI
NGS
0
22
0.0
TML
NGS
32
1025
3.1
TML
NGS
289
774
37.0
TML
NGS
3
97
3.1
NGS
63
1034
6.1
NGS
313
782
40.0
NGS
49
99
49.5
NGS
51
1036
4.9
NGS
20
801
2.0
NGS
43
99
43.4
NGS
1
601
0.2
NGS
27
782
4.0
NGS
48
99
48.5
NGS
0
1036
0.0
NGS
189
782
24.0
NGS
11
99
11.1
Fusion
3
28
10.7
NGS
197
782
25.0
PD-L1
IHC
21
139
15.1
Fusion
1
469
0.2
NGS
111
782
14.0
Fusion
3
470
0.6
NGS
47
782
6.0
Fusion
1
469
0.2
CNV
16
749
2.0
Fusion
1
28
3.6
PD-L1
IHC
452
1381
33.0
PD-L1
IHC
505
2386
21.2
HNSCC
BIOMARKERS
TECHNOLOGY
POSITIVE NO.
TOTAL NO.
PERCENT
MSI
NGS
1
164
0.6
TML
NGS
24
324
7.4
NGS
201
326
61.7
NGS
43
326
13.2
PD-1
IHC
250
340
73.5
PD-L1
IHC
255
721
35.4
Until recently, approved genetic testing involved a small group of genetic tests carried out in patients with specific cancers for a specific therapeutic purpose. Firmly established examples of mutational status being key to treatment recommendations include pan- testing (, , and ) in patients with CRC to direct the use of anti-EGFR therapies cetuximab and panitumumab45 and HER2 testing in patients with breast cancer to direct the use of anti–HER2-targeted therapies, such as trastuzumab,112 and tyrosine kinase inhibitor therapies, such as lapatinib.113 It took many years and a large number of trials involving many patients before pan- and HER2 testing became a standard treatment-predictive approach. Other examples of molecular testing used in standard clinical practice are detailed above (see Disease-Specific Biomarkers). However, as genetic testing evolved into whole genome sequencing, advances in computer technology allowed small-capacity assays to evolve into automated, high-throughput assays with large-scale data collection, classification, storage, and analysis. Thus, real-time, broad gene panel testing combined with relevant patient clinical data are now providing an unprecedented wealth of information. However, the interpretation of the meaning of results is limited by the finding that relatively small pools of evidence are available to validate most markers and their paired targeted therapies. Larger studies and collaborative efforts are certainly needed to further and more widely validate these broader panel markers and gene expression profiles and to integrate them and their targeted therapies into clinical practice (see Absence of Randomized, Controlled Clinical Trials, below). The immediate goal of testing is to translate genetic findings into potentially effective therapy decisions for today’s patients. Meanwhile, numerous proof-of-principle trials currently are in progress or in development. One key to accelerating the application of this knowledge is real-time national and international partnerships between cancer researchers and pharmaceutical companies to perform broad-panel profiling and elucidate targeted patient therapies. Concurrently, data pooling is mandatory using universal data-sharing capabilities to maximize the utility of these findings and generate large pools of evidence (see Data Sharing, below). Successes and failures alike will provide a more complete picture, and the result will take us steps closer to effective cancer treatment—and cures. This model is already in practice in the form of basket trials.
Oncology Basket Trials and Precision Medicine
Current oncology basket trials test therapies across a range of populations using biomarker-driven designs. Such trials choose biomarkers, which must have a clinically feasible assay, to attempt to enrich responses to a particular targeted therapy. The gathering of efficacy data across a range of populations translates to only one primary outcome endpoint, which simplifies the situation while increasing deductive power. These large-scale and small-scale, broad-panel molecular profiling trials include the National Cancer Institute’s Molecular Analysis for Therapy Choice (NCI-MATCH) trial, the American Society of Clinical Oncology (ASCO) Targeted Agent and Profiling Utilization Registry (TAPUR) study, and the European Organization for Research and Treatment of Cancer–Screening Patients for Efficient Clinical Trial Access (EORTC-SPECTA) program. These studies attempt to expand the boundaries of precision medicine and build evidence supporting the use of molecularly tailored therapy.
National Cancer Institute’s Molecular Analysis for Therapy Choice Trial
The novel, phase 2 NCI-MATCH (Molecular Analysis for Therapy Choice114) trial was initiated in August 2015 and is bringing public and private sectors together to enable access of physician researchers to investigational agents (in addition to approved agents) in an attempt to build the much sought-after evidence supporting the effectiveness of matching targeted therapy to patient molecular profiles. The primary aim of the NCI-MATCH study is to evaluate the proportion of patients with objective responses (ORs) to targeted therapies predicted to be mechanistically effective based on individual tumor genomic profiling. If the response rate to any mutation-matched therapy is at least 25%, this match will be tested in larger phase 2 trials. There are well over a thousand study locations across the United States, and pharmaceutical and biotechnology companies are providing targeted agents to enrolled patients across these sites. Patients are treated according to their profile (Table 7) and regardless of tissue origin or cancer type. New drugs of interest can be added to the “master” trial at any time. The trial is running under ClinicalTrials.gov identifier NCT02465060, where up-to-date information can be obtained.
Table 7.
Broadening Molecular Profiling Boundaries—Biomarker-Targeted Therapy Matches
TARGETED MUTATION
DRUG
NCI-MATCH trial: NCT02465060a
activating mutation
Afatinib
activating mutation
Afatinib
or mutations
Adavosertib (AZD1775)
FGFR pathway aberrations
AZD4547
, , mutation
Binimetinib
mutation
Capivasertib (AZD 5363)
mutation
Copanlisib
mutation
Copanlisib
loss
Copanlisib
amplification
Crizotinib
exon 14 deletion
Crizotinib
translocation
Crizotinib
translocation or inversion
Crizotinib
V600E/V600R/V600K/V600D mutation
Dabrafenib + trametinib
S768R, I638F, or L239R mutation
Dasatinib
inactivating mutation
Defactinib
mutation or deletion and PTEN expression
GSK2636771 (PI3Kβ inhibitor)
loss
GSK2636771 (PI3Kβ inhibitor)
mutation or fusion
Erdafitinib
amplification
Erdafitinib
, , gene fusions
Larotrectinib (LOXO-101)
Loss of or (by IHC)
Nivolumab
T790M or rare activating mutation
Osimertinib
, , amplification & Rb expression
Palbociclib
or amplification and Rb protein
Palbociclib
amplification ≥7 copy numbers
Pertuzumab + trastuzumab
or mutation
Sapanisertib
mutation
Sapanisertib
exon 9, 11, 13, or 14 mutation
Sunitinib
mutation
Taselisib
/ mutation
Trametinib
fusion or non-V600 mutation
Trametinib
mutation
Trametinib
amplification
Trastuzumab emtansine
/ mutation
Vismodegib
TAPUR trial: NCT02693535b
mutation, amplification or overexpression
Axitinib
, , , mutations
Bosutinib
, , mutations
Crizotinib
, , and (all wild type)
Cetuximab
, , , , , , , mutations
Dasatinib
inactivating mutations; mutations/deletions
Olaparib
MSI-high, high TML, and others
Nivolumab and ipilimumab
, , amplifications
Palbociclib
/ mutations; high TML
Pembrolizumab
1, 2, 3, , , , , mutations/amplifications
Regorafenib
, ,
Sunitinib
, mutations
Temsirolimus
amplifications
Trastuzumab and pertuzumab
V600E mutations
Vemurafenib and cobimetinib
Targeted Agent and Profiling Utilization Registry
The TAPUR study is an ongoing, nonrandomized, multicenter clinical trial that opened in 2016.115 This trial is testing the use of drugs already approved by the FDA that target a specific tumor mutation in individuals with advanced cancer outside of the drug’s approved indication. Patients with a range of solid tumors as well as lymphomas and multiple myelomas are eligible for enrollment. As with NCI-MATCH, treatment assignment in this study is based on an existing tumor mutation and not the organ from which the cancer originated. The study aim is to observe the real-world use of targeted therapies in any patient whose tumor tests positive for a selected genomic alteration that is known to be a drug target or has been shown to predict sensitivity to a drug available in this study. The primary outcome measure is the objective response rate (defined as the percentage of participants in a cohort with a complete or partial response at 8 weeks postbaseline or with stable disease at 16 weeks or later postbaseline according to RECIST (Response Evaluation Criteria in Solid Tumors) (for solid tumors), international uniform response criteria (for multiple myeloma),116 and Lugano criteria (for non–Hodgkin lymphoma).117, 118 Table 7 details the genomic alterations (biomarkers) and targeted therapies of interest at the time of submission of this article for publication, although markers and therapies are continually being refined as the study progresses. It is currently anticipated that TAPUR will enroll over 2500 patients in total. The trial is running under ClinicalTrials.gov identifier NCT02693535, where up-to-date information can be obtained.
European Organization for Research and Treatment of Cancer–Screening Patients for Efficient Clinical Trial Access
EORTC-SPECTA is a collaborative European molecular screening program that coordinates several disease-specific platforms with the aim of identifying actionable mutations and offering specific targeted therapy to patients (ClinicalTrials.gov identifier NCT02834884).119, 120 This is a large-scale basket trial that operates through one entry point that provides access to multiple studies and to high-quality, annotated material for research purposes and provides longitudinal follow-up of patients to understand progression patterns.121
Targets of Special Interest: Emerging and in Current Practice
There are several novel biomarkers of great interest, many of which have found a niche in common practice but are continuing to reveal exciting connections and uses. We expand on several these markers below.
Immune Markers and Immunotherapy
Programmed death–ligand 1 expression
122123124125, 12612742128129, 130
- First, performing a PD-L1 IHC assay on a single tumor site at one time point does not take into account the intrapatient tumor heterogeneity that can exist and the variability in PD-L1 expression that can occur over time.131132
- A second issue is the range of antibody assays that have been developed124133, 134
- A final issue is related to PD-L1 IHC scoring: how does one define a PD-L1–positive from a PD-L1–negative tumor? PD-L1 staining of immune cells in the tumor microenvironment, such as macrophages, gives a signal that is erroneously included in tumor PD-L1 assessment. This is the case for 22C3 and SP142 assays. To date, no approaches or thresholds reach sufficient sensitivity or specificity to be predictive of a high likelihood of response to a given drug. Providers need to be familiar with the individual PD-L1 assays and scoring used for each agent and tumor type when making patient decisions based on PD-L1 results.
The immune checkpoint PD-1/PD-L1 axis is a well-described inhibitory pathway that leads to T-cell exhaustion in the tumor microenvironment.Typically, PD-1 on tumor-infiltrating cytotoxic T cells interacts with PD-L1 on tumor cells, causing dampening of antitumor immunity (an adaptive immune response).Tumor types known to be immunogenic typically have relatively high rates of PD-L1 positivity.However, although greater clinical activity of anti–PD-1 agents (nivolumab and pembrolizumab) and PD-L1 agents (avelumab, atezolizumab, and durvalumab) has been consistently observed in patients with PD-L1–positive disease,some clinical trials have found that patients with low PD-L1–expressing tumors can derive significant benefit from anti–PD-1/PD-L1 agents. Therefore, PD-L1 IHC score alone is insufficient for patient selection in many tumor types. Assays have been developed to test for PD-L1 expression, including the PD-L1 IHC assay with 28-8 Dako (developed for nivolumab), 22C3 Dako (developed for pembrolizumab), SP142 Ventana (atezolizumab), SP263 Ventana (durvalumab), and 73-10 Dako (avelumab). These assays can be used as a tool for physicians to assess which patients might have the largest chance of benefitting from anti–PD-1/PD-L1 agents. However, because each inhibitor requires its own individual PD-L1 IHC assay, it is useful to have an upfront working knowledge of which targeted therapy is going to be used; otherwise the laboratory is required to run 5 different IHC tests, which raises costs and inefficiencies. There are several scenarios in which the FDA has mandated that PD-L1 positivity is required before anti–PD-1 agents are usable within approved indications. For example, patients with advanced, metastatic NSCLC can be treated in the front line with pembrolizumab monotherapy only if their PD-L1 tumor proportion score (TPS) is >50% (Table 2.1 ).In the second-line setting, pembrolizumab is FDA approved for adult patients with tumors (eg, gastric tumors) (Table 2.3 ) that have a lower positive TPS score (>1%).Interestingly, nivolumab has been approved as second-line therapy for select cancers regardless of their PD-L1 status.There is controversy over the use and reliability of PD-L1 IHC as a predictive biomarker. This is because of multiple factors:
Microsatellite instability and deficient MMR
Microsatellites are lengths of DNA sequence that contain single nucleotide (mononucleotide) or sections of 2 or more nucleotide (dinucleotide, trinucleotide, tetranucleotide, or pentanucleotide) repeats (see Microsatellite instability-high tumors and DNA mismatch repair). When microsatellites contain a clonal change in several repeated DNA nucleotide units, this results in MSI (tumors with such MSI are characterized as MSI-H, and this occurs when at least one of the MMR genes—, , , and —are inactivated, causing dMMR).10 Since MSI-H was established as a possible biomarker, the MSI status of a tumor has always required microdissection and PCR-based detection strategies. For practical purposes, MSI is equivalent to the loss of staining by IHC of at least one of the MMR genes because any lack of normal MMR protein expression signifies an abnormality in MMR and thus MSI. A sensitive and specific MSI assay by NGS has recently been developed that is comparable to the existing gold standard of PCR-based methods without requiring matched samples from tumor and normal tissues.10 MSI appears to be a generalized cancer phenotype in about 4% of all adult cancers in total. MSI-H tumors are associated with an improved prognosis in early-stage cancers. In Table 3,10, 11 MSI-H frequency data for several different cancer types are compared between 2 studies. In both studies, patient DNA was originally sequenced by NGS; however, the study by Bonneville et al11 obtained and retrospectively assessed sequencing data from The Cancer Genome Atlas (TCGA), the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database, and 444 other studies, whereas the study by Vanderwalde et al10 retrospectively assessed data from commercial comprehensive sequencing profiles performed on patient tumors by Caris Life Sciences. It can be readily observed from Table 310, 11 that the rate of MSI-H in tumors from different tissue types is not always consistent between studies. In particular, this can be observed for gastric cancers, endometrial cancers, breast cancers, and CRCs versus colon and rectal cancers. These study differences could be explained for the most part by sampling bias, the use of different data analysis techniques, or statistical variance. Vanderwalde et al10 certainly assessed a very sick patient population that was undergoing tumor profiling because of a bad prognosis and lack of obvious therapeutic options, whereas the patient population examined by Bonneville et al11 was not described as such and possibly consisted of patients with variable disease stages and prognoses; MSI-H patients tend to have a better prognosis than their microsatellite stable counterparts do, which would explain the lower percentage of MSI-H patients in the Caris data set compared with the TCGA data set. In addition, Vanderwalde et al10 combined colon and rectal cases in one analysis, possibly yielding a lower percentage of MSI-H than that seen by Bonneville et al11 for colon cancer alone. This highlights the potential for variability in biomarker assessment because of different assay types and technologies, not just for MSI but also across the biomarker board.
The role of TMB—an emerging biomarker
TMB is certainly an interesting marker, and evidence of its importance is growing. However, methodologies assessing TMB are not widely available at present, and most clinical laboratories do not yet offer this assessment in their assay repertoire. Immunogenicity is certainly associated with mutation load, suggesting that an increase in the number of somatic mutations present in tumor cells increases potential recognition by the immune system.135 Indeed, the presence of mutations in the tumor generates neoantigens (not expressed by normal cells), and the more mutations there are, the more the tumor is likely to be immunogenic. Furthermore, emerging evidence suggests that a high TMB is associated with increased clinical activity of immune checkpoint inhibitors.136–140 TMB was shown to predict immune therapy efficacy in patients with melanoma,138 NSCLC,140 and GI cancers.141 There is ongoing discussion regarding the definition of “high” TMB for predictive purposes. Most studies report ≥17 mutations per MB as high TMB, which is based on comparing TMB with MSI in patients with CRC. This, of course, also shows that high TMB is in strong concordance with MSI-high in CRC. However, although TMB is associated with dMMR, not all tumors with a high TMB are actually associated with MSI-H, and future studies should address this aspect.
MSI and MMR, TMB, and PD-L1
The relationship between TMB, MSI, and PD-L1 has recently been explored in a broad range of cancer types (Fig. 1).10 There is some overlap of all 3 markers in a few cancers. However, in most cancers, overlap is infrequent or does not exist at all, and 69.5% of all cancer cases were negative for all 3 biomarkers (7890 of 11,348 tested). A population of tumors exhibiting MSI-H status but low TMB and no PD-L1 expression was identified. Since MSI/MMR status alone or in combination with PD-L1 positivity became an accepted predictive marker in the FDA indication for checkpoint inhibitors, the finding that patients can test positively for only one of these markers obviously means that the number of patients now eligible to receive and hopefully benefit from checkpoint inhibition has been broadened. Until more is understood about how MSI, PD-L1, and TMB work together and how this interaction is clinically relevant, the only reasonable option is to continue to assay for all 3 markers and ensure that the number of patients who are given the chance to benefit from these drugs is maximized.
Figure 1Open in figure viewer
PowerPoint
10
Venn Diagram of the Relationships Between High Tumor Mutational Burden (TMB), High Microsatellite Instability (MSI-H), and High Programmed Death–Ligand 1 (PD-L1) for All Cancer Types.
Polybromo 1
PBRM1 is a non–MSI/PD-L1/TMB marker that could be predictive for response to checkpoint inhibitors. For example, clear cell renal cell carcinoma (ccRCC) responds to immune therapy but, unlike many other responsive human tumors, harbors a low burden of somatic mutations. Even so, ccRCC has relatively high immune cytolytic activity and a microenvironment with high immune and T-cell infiltration scores. In the past, large-scale sequencing studies demonstrated that loss of function (LOF) alterations are present in a large portion (up to 41%) of ccRCC tumors. Patients whose tumors had loss in both gene copies had significantly prolonged OS and PFS and manifested reduced tumor burden in response to immune checkpoint therapy compared with patients without loss (log-rank = .0074 and = .029, respectively). Miao et al summarized that, given the high prevalence of LOF in ccRCC, this genetic mutation has important implications as a molecular tool for considering immune therapy responsiveness in ccRCC and possibly across other cancer types.142
The Role of HRD as an Emerging Biomarker
Repair of DNA double-strand breaks by cells is mediated by the HR pathway or nonhomologous end-joining. HR is a complex DNA repair pathway involving multiple steps and has been reviewed extensively.143, 144 The and genes are critical for efficient double-strand DNA repair via HR and play an important role in the development and clinical progression of many cancers.145, 146 If a cell carries LOF mutations, it loses the ability to repair double-strand breaks by HR and is termed the HRD pathway. Such HRD cells are highly sensitive to DNA-damaging agents, such as platinum-based chemotherapies and other cytotoxic agents that can cause DNA strand breaks.147, 148 PARP plays a major role in DNA strand break repair. If PARP is inhibited, then cells ultimately die. Thus combining cytotoxic therapy with a PARP inhibitor can cause cell lethality.
Apart from mutations in the and genes, there are several other mechanisms associated with HRD. Defects in HR repair can be because of epigenetic changes such as promoter methylation, somatic mutations in key HR-related genes, and frequent copy number alterations.149 In addition, mutations in other genes may result in HR-defective tumors and include but are not limited to and .150–153
The most common approach to test for HRD is genomic testing for alterations in and on the basis that and germline and somatic mutations are known to cause HRD. Testing for additional genes involved in DNA damage repair through HR can also be done through commercial resources. Several other approaches have been developed to measure tumor DNA repair function.154 The myChoice HRD test is an NGS assay that uses DNA extracted from formalin-fixed, paraffin-embedded or frozen tumor tissue. A tumor can be characterized as HR-deficient or HR-nondeficient by combining the HRD score that it generates and its mutation status. HRD is defined as an HRD score ≥42 or the presence of a mutation in . As an example of its accuracy, the myChoice HRD assay was seen to identify 100% of BRCA-mutated tumors and 57% of non–BRCA-mutated tumors that had HR deficiencies in patients with platinum-sensitive, high-grade, serous or BRCA-mutated, recurrent ovarian cancer.65
The FoundationFocus CDx (Foundation Medicine, Inc) assay was used to detect both germline and somatic mutation types associated with response to PARP inhibitor therapy.155, 156 This modified NGS-based assay determined the percentage of genomic loss of heterozygosity, mutations in , and other HR genes in tumor tissue of patients with ovarian cancers taking part in the ARIEL PARP inhibitor rucaparib trial. A prespecified cutoff of ≥14% for high loss of heterozygosity was determined. FoundationFocus CDx is the first FDA-approved companion diagnostic assay for rucaparib for the treatment of advanced ovarian cancer.
As we understand more about HRD in various cancer types, the indications for the use of PARP inhibitors will likely be broadened. Certain cancers, including ovarian, fallopian tube, breast, primary peritoneal, and GI (specifically a subgroup of pancreatic adenocarcinomas and gastric/esophageal cancers), have been shown to harbor aberrations in genes involved in the HRD pathway. Mutations are seen not only in and but also in other relevant genes, such as , or .157, 158 Several PARP inhibitors have been FDA approved for the treatment of specific types of ovarian (olaparib, rucaparib, and niraparib), fallopian tube (olaparib and niraparib), breast (olaparib), primary peritoneal (olaparib and niraparib), and pancreatic (olaparib) cancers, but not yet for other GI cancers. However, at present, HRD testing before PARP-inhibitor therapy is not necessary.
Other Hot Markers in Research
Although it is not by any means an exhaustive list, some exciting new biomarkers and their targeted therapies are discussed below.
and Entrectinib
Entrectinib (RXDX-101) was granted a breakthrough therapy designation by the FDA in 2017 for use as a treatment for adult and pediatric patients with -positive, locally advanced or metastatic solid tumors who have either progressed after prior therapies or who have no acceptable standard therapy options (see also Neurotrophic receptor tyrosine kinase, above).27, 28 A trial studying the treatment of patients with solid tumors (breast cancer, cholangiocarcinoma, CRC, head and neck neoplasms, melanoma, neuroendocrine tumors, NSCLC, ovarian cancer, pancreatic cancer, papillary thyroid cancer, primary brain tumors, renal cell carcinoma, and sarcomas) that harbor an , , or fusion is ongoing (ClinicalTrials.gov identifier NCT02568267). In this trial, patients are assigned to different baskets according to tumor type and gene fusion. The primary outcome of the study will be the objective response rate to entrectinib.27
fusions may act as actionable targets in conjunction with other potentially targetable alterations, such as PD-L1–positive or MSI-H status, meaning that therapeutic combinations (TRK inhibitors plus immune checkpoint inhibitors, for example) are a promising strategy.159
and Erdafitinib
The fibroblast growth factor receptor (FGFR) family comprises part of a tyrosine kinase signaling pathway that plays a role in oncogenesis through gene amplification, activating mutations, or translocation in several tumor types. Erdafitinib is an orally administered FGFR family tyrosine kinase inhibitor. Earlier this year, the FDA granted Breakthrough Therapy Designation for erdafitinib in the treatment of urothelial cancer, which is based on data from a multicenter phase 2 clinical trial focused on evaluating the efficacy and safety of erdafitinib in the treatment of adult patients with locally advanced or metastatic urothelial cancer harboring specific mutations.160 The overall response rate was 42% in 59 patients for whom data were available.160 Erdafitinib is also under investigation in the NCI-MATCH trial as a treatment for patients with tumors that have an mutation, fusion, or amplification (Table 7).
Also in the NCI-MATCH trial, 5 of 50 patients with an aberrant FGFR pathway had a partial response to AZD4547 (another FGFR tyrosine kinase inhibitor).161 Two of these patient’s tumors had point mutations in , and 2 others had fusions, suggesting that these particular types of mutation have increased sensitivity to the drug, which warrants further study in this patient subtype.
Amplification and Exon 14 and Crizotinib
Aberrant activation of MET receptor tyrosine kinase signaling occurs in various cancer types as result of various alterations, including amplification and an exon 14 mutation. Crizotinib is an ALK/ROS1/MET inhibitor that is already FDA approved in -positive or -positive NSCLC but also has proven clinical activity in cases of exon 14 alterations and amplification. Preclinical studies have shown that inhibition of MET using crizotinib resulted in the inhibition of growth of cancer cells that possessed amplification both in vitro in cell lines and in vivo in preclinical models.162 In an updated phase 1 analysis of crizotinib in patients with low, medium, and high levels of amplification in advanced NSCLC, patients with high amplification showed clinically meaningful antitumor activity with rapid and durable responses. Crizotinib was generally well tolerated163 and is currently under study in the ASCO TAPUR trial for patients with tumors that have , , or mutations and in the NCI-MATCH trial as a treatment for patients with tumors that have a amplification, exon 14 mutation, translocation, or translocation or inversion (Table 7).
mTOR and Sapanisertib (TAK-228)
The mammalian target of rapamycin (mTOR) is a kinase encoded in humans by . mTOR exists as a core component in 2 distinct multiple-protein complexes, TORC1 and TORC2. These complexes regulate several different cellular processes, including cell proliferation, cell motility, cell survival, protein synthesis, autophagy, and transcription. Sapanisertib (TAK-228) demonstrated a reasonable safety profile as well as promising preliminary antitumor activity in a range of tumor types with aberrant .164 Tuberous sclerosis complex 1 and 2 ( and ) mutations are also observed in certain tumor subtypes and may be targeted by sapanisertib. The agent is under investigation in the NCI-MATCH trial as a treatment for patients with tumors that have or mutations (Table 7).
and Taselisib
In the NCI-MATCH trial, 65 patients with a mutated phosphatidylinositol 3-kinase gene () were treated with taselisib (a PIK3CA inhibitor) and, although there were no ORs to the drug, 24% of patients had prolonged stable disease for more than 6 months. Further research in selected cancer types is warranted.165
and Palbociclib
The cyclin-dependent kinases (CDKs) CDK4 and CDK6 play a crucial role in the G1-S phase transition during cell cycling. Palbociclib, an inhibitor of aberrant CDK4/CDK6, is FDA approved for the treatment of hormone receptor–positive, HER2-negative, advanced or metastatic breast cancer in combination with an aromatase inhibitor as initial endocrine-based therapy in postmenopausal women.166 Its effect on certain GI tumors is under investigation in the clinic.167 Palbociclib is also under investigation in the NCI-MATCH trial as a treatment for patients with tumors that have or amplification or , , or amplification (and Rb expression/protein in both study arms). The ASCO TAPUR trial is also investigating palbociclib in the treatment of patients with tumors that harbor , , or amplifications (Table 7).
and Dasatinib
DDR2 is a transmembrane receptor tyrosine kinase that plays a role in cancer progression by regulating the interactions of tumor cells with their surrounding collagen matrix. mutations are seen in several tumor types, including lung cancer, breast cancer, brain cancer, gynecologic cancer, and prostate cancer.168 The multikinase inhibitor dasatinib blocks DDR2 kinase activity to various degrees and is under investigation in the treatment of patients with tumors that possess a S768R, I638F, or L239R mutation (NCI-MATCH). The agent is also under investigation in the treatment of patients with tumors that harbor , or mutations (TAPUR trial) (Table 7).
Emerging Techniques
The Liquid Biopsy: Circulating Tumor Cells and Exosomes
Peripheral blood samples are a biomarker source by way of circulating tumor cells (DNA) and circulating nucleic acids or associated extracellular vesicles or exosomes.169–171 The use of liquid biopsy profiling has proven useful in selected clinical scenarios but, to date, despite its potential in the management of patients with most metastatic solid tumors, this technique has not established a firm role in standard practice. Obvious advantages include ease of access to the tissue through a simple blood draw. An additional advantage is that circulating samples may help reduce the problem of tumor heterogeneity as it reflects the sum total of the tumor. However, when blood and tumor tissue are concurrently collected and analyzed, results from circulating tumor cell analyses do not always match those obtained from tumor tissue analyses and thus are not always reliable.
Regarding extracellular vesicles or exosomes, a newly developed, minimally invasive ADAPT Biotargeting System characterizes complex biological systems in their inherent state(s) and relies on the fact that a large number of cells in the body secrete extracellular vesicles into the circulation, and the molecular composition of these “exosomes” correlates with the cell of origin. Through intercellular communication, exosomes play a part in controlling many tumor progressive processes, including immune evasion, angiogenesis, and metastasis.171 The ADAPT assay has been shown to have potential for biomarker identification and therapeutic use across most cancer types.171, 172
Community Hospital Molecular Testing and Assessment Program
Because 85% of cancer care is delivered in a community setting, it is imperative that the programmatic decisions concerning molecular testing for cancer include standardization, physician engagement, and application to point of care. Hoag Hospital (a large community hospital in Newport Beach, California) decided to embark on an initiative within the context of precision oncology and identified the need for molecular testing. A committee of interested physicians (including molecular pathologists) and administrators was formed, and a request for proposal was developed and put to several CLIA-certified vendors to outsource genomic testing. Certain specific qualifications were emphasized, such as price point; turnaround time; results reporting and support structure; portfolio of testing, including NGS, CNV, and IHC for protein analysis and fusion genes (all preferably using disease-specific panels); and preauthorization and billing services. Several meetings were required to reach a final decision. Once the vendor was selected and contracting was optimized, all tumor molecular testing was standardized, and all ordering and tissue processing was sent through the central pathology laboratory. It is important to note that this process had immediate benefit for the cancer programs because, before this arrangement, molecular testing was haphazard. Tumor tissue samples were being sent by individual physicians to multiple different laboratories/vendors without standardization of tissue collection and processing, and subsequent result reports were generally faxed and unavailable when needed for valuable treatment assessment in the standard clinical or research settings.
After vetting and education concerning this new molecular testing and assessment program at disease site committee and tumor board meetings, it was further decided that genomic testing would be reflexed and ordered by pathology for selected clinical stages of solid tumors. The initial pilot project for this reflex testing was in NSCLC stages IB through IV. Before this initial pilot of genomic reflex testing in lung cancer, approximately 50% of the tumors in patients with advanced lung cancer were being tested for even the minimal NCCN guideline biomarkers. Now, over 95% of advanced lung cancers undergo genomic profiling evaluation that has resulted in pervasive use at the point of care. An illustrated example of this was a recent patient’s lung cancer demonstrating an actionable mutation in . The success of this pilot study in reflex profiling has expanded to other cancer disease sites, such as advanced head and neck cancers, ovarian cancers, glioblastoma multiforme, sarcoma, and rare tumors. Over the past 18 months, more than 300 tumors have undergone clinical grade genomic profiling, and those data are readily available to the treating physician through web access. Importantly, physician education is a key component to the establishment of a comprehensive cancer molecular genomics program. Initiation of the more routine use of molecular markers and genomic profiling has stimulated interest and participation in the expanding clinical applications. Along with the assistance of molecular pathology, presentation of genomic data is now frequently requested, and this provides points of discussion in the cancer disease site tumor board meetings. In addition, this information has led to optimal patient selection and a definitive increase in referrals to the phase 1 clinical trials program.
Despite the successful implementation of this intuitional program in cancer molecular testing, challenges remain. These fall into several categories, such as reimbursement issues, evaluating the tumor genomic data for potential germline testing, paring results to clinical trial opportunities, and collecting and collating the genomic data to clinical information and outcomes, as well as the incorporation of new opportunities such as sequencing cell-free DNA or routine pharmacogenetic testing. The overall goal of this program was to provide added value and physician engagement in precision oncology. This is now a work in progress, but we are already evaluating the growth opportunity to enhanced patient care.
Challenges and Open Questions in Molecular Profiling
Absence of Randomized, Controlled Clinical Trials
One of the major challenges with the use of large panels or whole genome sequencing is the absence of randomized clinical trials demonstrating benefit. Although some retrospective analyses have appeared promising, in general, the field demands more evidence given the expense of drugs and genomic tests and potential harm from exposing patients to toxicity of drugs without proof of efficacy. A properly performed randomized clinical trial requires a large number of patients and needs to be a national study requiring significant resources to cover costs of testing, cost of drugs, and data analysis. It would be problematic to randomize patients to genomic profiling versus no testing. It is also complicated to compare standard therapy with molecularly assigned therapy in terms of comparing apples to apples and defining what the valid endpoints should be. It is clear that the gold standard is OS, but this may be affected by multiple lines of therapy and ultimate use of targeted therapy beyond a particular study. PFS is a reasonable endpoint but, if the randomization occurs at a time when there is effective standard therapy, then the impact of molecularly targeted therapy may be underestimated. With the era of precision oncology, there is opportunity to break new ground in trial design. In this regard, pooling N-of-one data that account for other factors described below, such as tumor heterogeneity, may allow for useful evidence to help patients even if it does not rise to randomization. In addition, the PFS ratio as defined by Von Hoff remains a good metric to determine benefit of molecularly assigned therapy.
Lack of Drugs
Another major challenge is the lack of availability of drugs for numerous drivers of various cancers. Examples of major drivers for which there are currently no approved drugs include mutated β-catenin, mutated , or mutated , among others. On the optimistic side, as drugs are discovered and developed, they can be offered retrospectively to patients who have actionable mutations. A related issue is the lack of drugs that effectively target emergent resistance mechanisms. There are some exceptions with mutated , , or .
Tumor Heterogeneity
It is clear that advanced cancers, especially those that have been treated, harbor significant tumor heterogeneity. This includes intralesion heterogeneity, interlesion heterogeneity, and interpatient heterogeneity, all of which complicate treatment recommendations and outcomes of studies.
Platform Heterogeneity
In clinical practice, there are several different available platforms for molecular profiling; each test has its own sensitivity and specificity. The scope of the testing varies in the number of genes, whether RNA or protein expression is assessed, and whether actionable fusions are readily detectable. Such heterogeneity makes it difficult to pool data from different platforms. The various commercial platforms or those performed within academic institutions are continuously evolving, further complicating the issue of platform heterogeneity. Thus older platforms that did not capture actionable targets for which there are effective therapies lead to data sets that may underestimate the value of genomic testing with respect to patient outcomes. Moreover, no study to date has shown that larger panels are worth doing over smaller targeted gene panels that are part of standard of care (eg, , , , and MSI in CRC). However, it is not unreasonable to expect that the many genomic changes representing the tail end of the curve of drivers may affect patient outcomes, especially if there are available drugs that target their pathways. With the emergence and popularity of liquid biopsy, this yet further adds complexity to the platforms. Of note, in the TAPUR study, which models real-life situations, liquid biopsy is acceptable for the identification of actionable targets to allow enrollment in a treatment arm.
CLIA-approved laboratories offering molecular panel analysis
Before a patient sample of any kind can be tested, the assay in question must be validated in a CLIA-certified laboratory. CLIA defines a clinical laboratory as any facility that performs laboratory testing on specimens derived from humans for the purpose of providing information for the diagnosis, prevention, or treatment of a disease or impairment. The CMS regulates all laboratory testing performed on humans in the United States through the CLIA program. In total, CLIA covers approximately 260,000 laboratory entities. The Division of Clinical Laboratory Improvement and Quality, within the Quality, Safety, and Oversight Group under the Center for Clinical Standards and Quality, has responsibility for implementing the CLIA program. The objective of the CLIA program is to ensure quality laboratory testing. Although all clinical laboratories must be properly certified to receive Medicare or Medicaid payments, CLIA has no direct Medicare or Medicaid program responsibilities.
Clinical laboratories must constantly evolve their test offerings to support the most recent advances in cancer care. For NGS tumor profiling assays, there are multiple commercially available kits with similar claims for gene content and sensitivity. Many factors contribute to the decision of which assays or customized solutions will best meet the needs of the laboratory, clinicians, and patient population. Kit costs, capital equipment expenditures, complexity of workflow, and turnaround time are all important factors that can be relatively easily compared and assessed between assay systems. However, the more important parameters for determining effective, personalized treatment for patients are accuracy, reproducibility, and sensitivity of the assay, and these can be much more challenging to critically evaluate but must be rigorously validated.173–176 The use of a highly multiplexed, consistent, and well-characterized reference material greatly facilitates the comparison of assay systems.177
Data Sharing
Given the numerous challenges described above and others, including limitations of electronic medical records, issues with intellectual property, commercial interests, Health Insurance Portability and Accountability Act of 1996 (HIPAA) regulations, and quality of clinical outcomes data, there are major difficulties with data sharing to expand data sets through larger sample size. In this regard, the Caris Precision Oncology Alliance has been addressing some of the issues through the CODE database, which is increasing the number of patients for whom analysis of clinical outcomes is possible as a function of clinical, genomic, or drug use. Other initiatives of national prominence include Orion, Project GENIE, the WIN Consortium, the Precision Medicine Exchange Consortium, and the Memorial Sloan Kettering (MSK) Cancer Alliance.
Timing
The ideal time to perform genomic testing to maximize its therapeutic value to individual patients with cancer remains a matter of controversy, and the evidence base on which to make recommendations is still evolving. Initially, physicians mainly ordered testing in patients with advanced disease who had exhausted standard-of-care treatment options to help inform choices for treatment with experimental agents. Trials are now underway in groups of patients with earlier stages of disease. For example, the newly activated, NCI-sponsored intergroup stage III colon cancer adjuvant therapy trial randomizes patients to standard adjuvant therapy with FOLFOX or FOLFOX plus experimental treatment with a PD-1 inhibitor. Only patients with MSI-H, stage III colon cancer will be eligible for randomization, and the eligibility determination mandates genomic testing for defective MMR in patients with localized disease. Commercial genomic testing now includes MSI testing in addition to a battery of genes relevant to tumor progression. The addition of MSI testing to these panels is a consequence of the recent approval of pembrolizumab and nivolumab. The agents are currently approved for the treatment of refractory tumors of any histology that exhibit defective MMR.141 In patients with advanced cancers, it is clear that the tumor genome continues to evolve with time and with the pressure exerted on cells by treatments that selectively favor the growth of treatment-resistant subclones.178 Investigators remain concerned about clonal evolution and often will recommend rebiopsy of tumors when patients have refractory disease to ensure that the genomic analysis used to make informed decisions about clinical trials with targeted agents is reflective of the tumor’s current biology.179 Others suggest testing at the first sign of advanced disease, as the efficacy of conventional chemotherapy is variable and strategies for salvage therapy may be required sooner rather than later. The use of “liquid biopsies” either on circulating tumor cells or on cell-free DNA has been touted as a method of assessing the tumor genome without the need for a repeat, invasive biopsy. This remains a research tool at this time and is not generally a part of clinical practice. Continued data analyses are urgently needed and will inevitably occur as more samples are tested and the practical application of these assessments are translated into treatment decisions.
Discussion
In 2019, optimum cancer care requires state-of-the-art molecular diagnostics, a solid knowledge base to interpret and apply the results, and a nearly constant awareness of changes on the horizon. The field is moving that quickly. Comprehensive testing performed on our patients at the beginning of 2019 is likely to be incomplete today. Drug approvals are no longer based solely on large phase 3 trials; these late-stage trials are being replaced by “basket” and “umbrella” trials, allowing us to ensure that the right drug is given to the right patient faster. Subsequent new regulatory and payer approvals seem to come daily. Precision medicine is now a part of our standard practice, but with this comes many new challenges. How do we deal with tumor heterogeneity, and will liquid biopsies satisfactorily replace tissue-based testing? Are we justified in, and can we afford, testing a large sample of patients, knowing that we will only rarely find the sought after “needle in the haystack?” How do we manage our patients’ expectations when there is so much press and hype surrounding our new discoveries? Can we afford to develop and ultimately to pay for increasingly expensive therapies targeting increasingly smaller proportions of patients? There is, of course, no turning back, but there is much work ahead.
Acknowledgements
Marion L. Hartley, PhD, provided invaluable writing and editing support, table and bibliography creation, author coordination, and article organization. These medical writing activities were supported by Caris Life Sciences.
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