Policy Guidelines
Primary lung cancer is one of the most common malignancies. In the United States, approximately 226,650 individuals are diagnosed, and more than 124,730 deaths occur annually. Approximately 87 % of lung cancers are NSCLC and 13% are SCLC.
Specific molecular treatments for patients based on certain genetic mutations have been developed. Currently, EGFR, ALK, ROS1, BRAF, and NTRK-positive cases of NSCLC have FDA-approved targeted therapies (i.e. specific treatments for specific mutations), whereas HER2-, MET-, and RET-positive cases are treated with off-label therapies. Therapies for other mutations such as RAS, PTEN, AKT1, and PIK3CA mutations are currently in development. Still other genetic biomarkers, such as PD-L1 expression and microsatellite instability (MSI) testing may contribute to the management of NSCLC cases.
EGFR tyrosine kinase mutations are observed in approximately 15% of NSCLC adenocarcinoma cases in the United States and occur more frequently in nonsmokers. The presence of an EGFR mutation usually confers a better prognosis and may be treated by EGFR tyrosine kinase inhibitors. (TKIs) such as erlotinib.
ALK tyrosine kinase translocations are present in approximately 4% of NSCLC adenocarcinoma cases in the United States and occur more frequently in nonsmokers and younger patients. In advanced-stage NSCLC, the presence of an ALK translocation maybe treated by ALK TKIs such as crizotinib. Other effective TKIs include ceritinib, alectinib, brigatinib, and lorlatinib. Studies have indicated that treatment with these therapeutic TKIs significantly prolongs progression free survival.
ROS1 is a receptor tyrosine kinase that acts as a driver oncogene in 1 to 2% of NSCLC cases by a translocation between ROS1 and other genes, such as CD74. ROS1 translocations are usually associated with younger patients, and individuals who have never smoked tobacco. Since the ALK and ROS tyrosine kinases are significantly homologous, the ROS1 tyrosine kinase is treatable by ALK TKIs such as crizotinib.
HER2 (ERBB2) is an EGFR family receptor tyrosine kinase. Mutations in HER2 have been detected in approximately 1 to 3% of NSCLC tumors. These mutations are most frequent in exon 20, resulting primarily in adenocarcinomas. These mutations are more prevalent among individuals who have never smoked tobacco.
BRAF is a downstream signaling mediator of KRAS that activates the mitogen-activated protein kinase (MAPK) pathway. Activating BRAF mutations have been observed in 1 to 3% of NSCLC cases and are usually associated with smokers. BRAF inhibition with oral small-molecule TKIs has been used to treat this version of NSCLC.
MET is a tyrosine kinase receptor for hepatocyte growth factor (HGF). MET mutations include MET exon 14 skipping, MET gene amplification and MET and EGFR co-mutations. Tepotinib has shown evidence of promise in treating MET-exon 14 skipping cases. Crizotinib, an ALK/ROS inhibitor, has also been used to treat MET-exon 14 skipping cases of NSCLC. Other MET-specific, therapies are under investigation, such as glesatinib and savolitinib. For those with MET amplication, capmatinib or crizotinib are suggested lines of treatment, but are not yet approved for this indication by the FDA and continue to be a line of active research.
The RET gene encodes a cell surface tyrosine kinase receptor that may be translocated in adenocarcinomas. These mutations occur more frequently in younger patients and in individuals who have never smoked tobacco. Off-label RET inhibitors, such as alectinib, have been used to treat RET-positive cases of NSCLC. In addition, the FDA has approved selpercatinib and pralsetinib for advanced NSCLC in adult patients.
RAS mutations, in either KRAS or NRAS are associated with NSCLC. Activating KRAS mutations have been observed in approximately 20 to 25 % of lung adenocarcinomas in the United States and are generally associated with smoking. The presence of a KRAS mutation has a limited effect on overall survival in patients with early-stage NSCLC. NRAS is homologous to KRAS and associated with smoking as well; however, NRAS mutations comprise only 1% of NSCLC cases. The clinical significance of NRAS mutations is unclear, and no effective targeted therapies exist at this time.
PIK3CA, AKT1, PTEN are the three genes involved in the same pathway. PIK3CA encodes the catalytic subunit of phosphatidyl 3-kinase (PI3K), AKT1 acts immediately downstream of PI3K, and phosphatase and tensin homolog (PTEN) inhibits AKT by dephosphorylation. Oncogenic alterations in this pathway include gain-of-function mutations in PIK3CA and AKT1, and loss of PTEN function. PIK3CA mutations may also cause resistance to EGFR TKIs in EGFR-mutated NSCLC. Small-molecule inhibitors of PI3K and AKT are being developed, but clinical efficacy of these agents against specific molecular alterations is unknown.
Other genetic biomarkers include PD-L1 assessment and microsatellite instability (MSI) testing. Programmed death-1 ligand (PD-L1) expression testing via immunohistochemistry (IHC) is used to guide therapy for patients with NSCLC. Tumor cells present PD-L1 to T-cells to inhibit the immune response by downregulating cytokine production and T-cell proliferation, thereby allowing these tumor cells to evade immune system activity. Monoclonal antibody therapy (immune therapy) has been developed to inhibit this pathway and overcome this mechanism of immune system evasion. Tumor PD-L1 protein expression through immunohistochemistry can be ordered to pinpoint first-line treatment options for NSCLC outside of chemotherapy.
Microsatellites are short tandem repeat sequences located throughout the genome. However, these sequences are subject to instability caused by faulty mismatch repair genes. This has historically been reported in other cancers, such as Lynch syndrome, and has been reported in NSCLC. MSI testing may be used to evaluate NSCLC cases.
Precision oncology is now the evidence-based standard of care for the management of many advanced NSCLCs. Expert consensus guidelines have defined minimum requirements for routine testing and identification of epidermal growth factor (EGFR) and anaplastic lymphoma kinase (ALK) mutations) in advanced lung adenocarcinomas. Targeted use of TKIs based on certain genetic mutations has consistently led to more favorable outcomes compared with traditional cytotoxic agents. The concept of targeted testing has been approved by the FDA, as package inserts for drugs such as erlotinib specify use for EGFR mutations and other drugs such as pembrolizumab have gained approval for specific types of tumors (in this case, high-MSI tumors). Proprietary tests are available for identification of relevant mutations, including larger genetic panels. Foundation One’s 324-gene panel and Oncomine’s 23-gene panel are both FDA-approved as companion diagnostics for non-small cell lung cancer targeted therapies. Recently, Guardant 360 CDx was FDA-approved for use as a companion diagnostic to identify NSCLC patients with EGFR mutations who may benefit from Tagrisso (osimertinib). The company Cobas has a diagnostic approved to identify patients with metastatic NSCLC who might benefit from Tarceva® (erlotinib) based on formalin-fixed tissue preparation to identify EGFR mutation; a Cobas assay was also FDA approved as a companion diagnostic using liquid biopsy and circulating-free tumor DNA.
Clinical Utility and Validity
Lin et al. (2017) evaluated the association between EGFR and EGFR-TKI efficacy in stage IV NSCLC patients. In this study, 94 patients were assessed. The authors calculated a 74.5% objective response rate and a 97.9% disease control rate for EGFR-TKI treatment. The authors concluded that EGFR-TKI therapy resulted in survival benefits for EGFR-mutant patients regardless of “gender, smoking history, pathologic type, type of EGFR mutations, brain metastasis and timing of targeted therapy.”
Li et al. (2017) examined the effect of number of EGFR mutations on the efficacy of EGFR TKIs. In this study, 201 patients with EGFR mutations were evaluated. These patients were quantitatively separated into “low” and “high” groups based on “amplification refractory mutation system (ARMS) method optimized with competitive blockers and specific mutation quantitation (ARMS+)”. The cutoff value was determined by a receiving operating characteristic analysis in a training group and further validated in another group. The investigators found the median progression-free survival (PFS) to be 15 months in the high group compared to the two months in the low group. Similar results were reported in the validation group. The authors concluded that the abundance of EGFR mutations was significantly associated with objective response to EGFR TKIs. However, they also noted the abundance of EGFR T790M mutation may adversely affect PFS rather than objective response rate.
Wang et al. (2017) investigated the effect of ALK rearrangements on NSCLC patients. The authors reviewed 15 studies including 4981 patients. The study found that ALK positive (ALK+) patients faced better prognoses (hazard ratio 0.81 of ALK negative patients) except in the non-smoking population (hazard ratio 1.65). ALK+ patients also experienced a significantly higher objective response rate in pemetrexed-based chemotherapy, but not with EGFR-TKI treatment.
Gainor et al. (2016) performed a study evaluating the efficacy of PD-L1 blockades on EGFR and ALK positive patients. The study evaluated 58 patients; 28 had an EGFR or ALK mutation whereas 30 were wild-type. The investigators found only one of the 28 patients (3.6%) with either mutation had an objective response whereas seven of the 30 (23.3%) wild-type patients had an objective response.
Planchard et al. (2016) evaluated the efficacy of the FDA-approved combination of daBRAFenib plus trametinib on previously treated BRAF-mutant metastatic NSCLC. The study included 57 patients; 36 of these patients achieved an overall response. However, serious adverse events were reported in 32 of these patients. The authors concluded that this combination may represent a robust therapy with a management safety profile in BRAF-positive NSCLC patients.
Singal et al. (2019) examined the electronic health records (EHR) of 4064 individuals with NSCLC from 275 different oncology practices to explore “associations between tumor genomics and patient characteristics with clinical outcomes…” They note that 21.4% of these individuals had a mutation in EGFR, ALK, or ROS1, and that patients with driver mutations who had targeted therapies had significantly improved overall survival times than individuals who did not have targeted therapies (median of 18.6 versus 11.4 months, respectively); moreover, a tumor mutational burden (TMB) of 20 or higher was associated with improved overall survival for patients on PD-L1-targeted therapy than those patients with a TMB less than 20. The authors concluded that they replicated similar associations from previous research “between clinical and genomic characteristics, between driver mutations and response to targeted therapy, and between TMB and response to immunotherapy.
Siena et al. (2019) reported integrated data from three clinical trials focusing on entrectinib. Patients had either ROS1-driven or NTRK-driven cases of NSCLC. Out of 53 patients with ROS1 mutations, approximately 80% responded to entrectinib. Out of 54 patients with NTRK mutations, approximately 60% responded. The authors considered entrectinib to be “tolerable with a manageable safety profile,”
and concluded that “entrectinib induced clinically meaningful durable responses in [patients] with ROS1+ NSCLC or NTRK+ solid tumors with or without CNS disease.”
Volckmar et al. (2019) assessed the “feasibility and clinical utility of comprehensive, NGS-based genetic profiling for routine workup of advanced NSCLC”. The authors based their study on the first 3000 patients seen in their facility. Of the patients tested, the authors identified 807 patients eligible for “currently approved, EGFR-/BRAF-/ALK- and ROS1-directed therapies”, while 218 additional cases with MET, ERBB2 (HER2) and RET alterations could “potentially benefit from experimental targeted compounds”. Other co-mutations such as TP53 and STK11 were also frequently identified, which may be potentially useful predictive and prognostic tools. The authors also noted logistical successes, such as reliability, low dropout rate, fast turnaround times, and minimal tissue requirements. Overall, the authors concluded that this diagnostic approach demonstrated “practicability in order to support individualized decisions in routine patient care, enrollment in molecularly stratified clinical trials, as well as translational research.”
Signorovitch et al. (2019) aimed to evaluate the “budget impact of increased use of CGP [comprehensive genomic profiling] using a 324-gene panel (FoundationOne) vs non-CGP (represented by a mix of conventional molecular diagnostic testing and smaller NGS hotspot panels) and the number needed to test with CGP to gain 1 life year”. The authors developed a decision analytic model to assess the financial impact of increased CGP in advanced non-small cell lung cancer (NSCLC). The study included two million covered lives, of which 532 had advanced NSCLC. Of these patients, 266 underwent molecular diagnostic testing. An increased in CGP among those tested (from 2%-10%) was associated with a $0.02 per member per month budget impact, of which $0.013“was attributable to costs of prolonged drug treatment and survival and $0.005 to testing cost”. Overall, the addition of one life year was met with 12 patients tested. The authors concluded that a 2%-10% increase in CGP use was associated with a “modest budget impact, most of which was attributed to increased use of more effective treatment and prolonged survival.”
In a prospective study, Peled et al. (2020) investigated the clinical utility of early cell free deoxyribose nucleic acid (cfDNA) analysis using Guardant 360 CDx in treatment-naive NSCLC patients. Ten patients were studied and the median time from blood draw to receiving the cfDNA results was 9 days. Actionable biomarkers were identified in four of the ten patients by both biopsy analysis and cfDNA analysis. Overall, three patients received biomarker-based treatment (one osimertinib, one alectinib, and one crizotinib). The authors concluded that "cfDNA analysis should be ordered by the pulmonologists early in the evaluation of patients with NSCLC, which might complement the tumor biopsy.”
Al-Ahmadi et al. (2021) studied the overall impact and racial differences of NGS testing in NSCLC patients. The study tested 295 patients with Stage IV NSCLC using the Foundation One assay and genomic differences were compared by race. "Patients undergoing NGS testing had significantly longer survival of 25.3 months versus those who did not undergo sequencing with a median survival of 14.6 months (P=.002) irrespective if they received targeted therapy or not. In addition, there was no difference in NGS results based on race. However, African American patients had a higher rate of mutations in PBRM1, SETD2, TSC2, and FBXW7. Overall, there is no racial difference in NGS utilization and testing does increase survival.”
Boeckx et al. (2020) convened a small study of 46 never-smoking, non-small cell lung cancer (NSCLC) patients to investigate genomic alterations in non-smoking individuals. There are few genomic studies focused primarily on this subgroup of patients with NSCLC who have never smoked. Whole exome and low-coverage whole genome sequencing were performed on tumors and matched germline DNA. Fewer somatic mutations, genomic breakpoints, and a smaller percentage of the genome with chromosomal instability in lung tumors were observed in non-smokers compared to smokers. In addition, TSC22D1 was noted as a potential driver gene of NSCLC. The frequency of mutation of TP53, which is associated with negative long-term outcomes, was lower in those who were never-smokers than in smokers. That said, they found driver genes such as EGFR and ERBB2, as well as amplifications in MET were higher in never-smokers. The authors c concluded there was a “more favorable prognosis for never smokers with NSCLC.”
Qi, et al. (2024) studied the clinical validity of the Oncomine Dx Target (ODxT) Test to identify HER2 NSCLC. Tumor samples from patients enrolled in two clinical trials were used. Commercially available tumor samples were also used. The authors compared the results of the Oncomine Dx Target Test with the assay used in the clinical trials. The Oncomine Dx Target Test had a positive precent agreement of 100% and a negative precent agreement of 99.1%. “The ODxT Test results were highly concordant with clinical trial assays.” The authors concluded that “The ODxT Test detected HER2 mutations in NSCLC with high analytical and clinical accuracy and identified HER2m populations with response rates similar to populations identified by [clinical trial assays], supporting clinical utility of the ODxT Test to inform treatment decisions for HER2m NSCLC.”
Chen, et al. (2024) studied the clinical validity and utility of circulating tumor DNA (ctDNA) NGS as a tool for targeted treatment of advanced NSCLC. The authors conducted a systematic literature review and meta-analysis including 20 studies. For the detection of any mutation, the sensitivity of ctDNA was 0.69 and the specificity was 0.99. Sensitivity varied by gene: 0.29 for ROS1, 0.38 for RET, 0.47 for MET, 0.59 for ALK, 0.60 for BRAF, 0.68 for EGFR, and 0.77 for KRAS. The authors concluded that “ctDNA testing demonstrated an overall acceptable diagnostic accuracy in patients with [advanced NSCLC], however, sensitivity varied greatly by driver mutation.”
Guidelines and Recommendations
National Comprehensive Cancer Network (NCCN)
In the Version 3.2025 update for NSCLC, NCCN states, “Numerous gene alterations have been identified that impact therapy selection. Testing of lung cancer specimens for these alterations is important for identification of potentially efficacious targeted therapies, as well as avoidance of therapies unlikely to provide clinical benefit.” NCCN then expounds on their stance, providing a set of “several methodologies that are generally considerations for use” that is delineated below:
- Next-generation sequencing (NGS) is used in clinical laboratories. Not all types of alterations are detected by individual NGS assays and it is important to be familiar with the types of alterations identifiable in individual assays or combination(s) of assays.
- It is recommended at this time that when feasible, testing be performed via a broad, panel-based approach, most typically performed by (NGS). For patients who, in broad panel testing don’t have identifiable driver oncogenes (especially in never smokers), consider RNA-based NGS if not already performed, to maximize detection of fusion event.
- Real-time polymerase chain reaction (PCR) can be used in a highly targeted fashion (specific mutations targeted). When this technology is deployed, only those specific alterations that are targeted by the assay are assessed.
- Any method that interrogates sequences other than a subset of highly specific alterations (eg, NGS) has the potential to identify variants of uncertain significance (VUS). Any variant classified as a VUS, even if in a gene in which other variants are clinically actionable, should not be considered as a basis for therapy selection.
- Other methodologies may be utilized, including multiplex approaches not listed above. Fluorescence in situ hybridization (FISH) analysis is utilized for many assays examining copy number, amplification, and structural alterations such as gene rearrangements, FISH may have better sensitivity for gene amplification events in some circumstances.”
In order “To minimize tissue use and potential wastage, the NCCN NSCLC Panel recommends that broad molecular profiling be done as part of biomarker testing using a validated test(s) that assesses a minimum of the following potential genetic variants: ALK rearrangements; BRAF mutations, EGFR mutations, ERBB2 (HER2) mutations, KRAS mutations, MEex14 skipping mutations, NTRK1/2/3 gene fusions, RET rearrangements, and ROS1 rearrangements. Both FDA and laboratory-developed test platforms are available that address the need to evaluate these and other analytes. Broad molecular profiling is also recommended to identify rare driver mutations for which effective therapy may be available, such as high-level MET amplifications.
The NCCN also states that “First-line targeted therapy options are recommended for eligible patients with metastatic NSCLC and positive test results for actionable driver mutations such as: ALK, BRAF, p.V600E, EGFR, METex14 skipping, NTRK 1/2/3, RET and ROS1. “Second-line targeted therapy is recommended for patients with metastatic NSCLC and positive test results for EGFR exon 20 insertions or KRAS p.G12C mutations.”
In the 2022 NCCN update, the NCCN clarified that “any variant that is classified as VUS should not be used to select targeted therapy even if the VUS occurs in a gene in which other variants are clinically actionable.”
The NCCN Panel added important information about general standards for biomarker testing in eligible patients with NSCLC. They noted that broad molecular profiling is molecular testing that “identifies all of the classic actionable driver mutations described in the algorithm [eg. ALK, BRAF, EGFR, ERBB2 (HER2), KRAS, METex14 skipping, NTRK 1/2/3, RET, ROS1] using either a single assay or a combination of a limited number of assays—and optimally also identifies the emerging actionable molecular biomarkers, including high-level MET amplification. Tiered KRAS testing approaches, based on the low prevalence of co-occurring biomarkers, are acceptable.”
EGFR mutations
EGFR mutations are most often assessed using RT-PCR, and NGS. EGFR mutation status is important for determining use of tyrosine kinase inhibitor (TKI) therapies. EGFR mutations include, but are not limited to, exon 19 deletions, p.L858R point mutation, p.L861Q, p.G719X, p.S768I0, exon 20 insertion variants, and p.T790M. As a category 1 recommendation, EGFR mutation testing is recommended for advanced or metastatic disease, including adenocarcinoma, large cell, and NSCLC NOS. As a category 2A recommendation, it is recommended to consider it for individuals with squamous cell carcinoma who have never been smokers, small biopsy specimens, or mixed histology.
ALK gene rearrangements
ALK gene rearrangements are most often assessed using FISH, but IHC can also be effective. The NCCN states that NGS can detect ALK fusions, but PCR is less likely to detect any ALF fusion with a novel partner(s). The most common fusion partner for ALK is EML4; however, many other partners have been isolated and identified. Like EGFR, ALK status is used in determining whether TKI therapies are appropriate. As a category 1 recommendation, ALK testing is recommended for advanced or metastatic disease, including adenocarcinoma, large cell, and NSCLC NOS. As a category 2A recommendation, it is recommended to consider it for individuals with squamous cell carcinoma who have never been smokers, small biopsy specimens, or mixed histology.
ROS1 rearrangements
In NSCLC, ROS1 rearrangements can result in inappropriate ROS1 kinase signaling. Similar to ALK, FISH break-apart testing is often used, but this methodology “may under-detect the FIG-ROS1 variant.” IHC requires confirmatory testing because it has a low specificity for ROS1. PCR, if used, can be unlikely to detect novel fusion partners. The use of NGS can detect ROS1 fusions, but DNA based NGS is prone to under detection of ROS1 fusions. ROS1 status is important for responsiveness to oral ROS1 TKIs. As category 2A recommendations, ROS1 testing should be performed for advanced or metastatic disease, including adenocarcinoma, large cell, and NSCLC NOS; it should be considered in individuals with squamous cell carcinoma with small biopsy specimens or mixed histology. Entrectinib has been noted as a preferred treatment option for ROS1 rearrangements in advanced or metastatic NSCLC by the NCCN since 2019. However, it should be noted that “Targeted real-time PCR assays are utilized in some settings, although they are unlikely to detect fusions with novel partners.”
BRAF point mutations.
Sequencing methods, especially NGS, and rtPCR are most often used for detecting BRAF point mutations. BRAF V600 mutations are associated with responsiveness to certain combination therapies. Many BRAF mutations have been identified in NSCLC, but the impact of these mutations is not well-understood as of date. As category 2A recommendations, BRAF testing should be performed for advanced or metastatic disease, including adenocarcinoma, large cell, and NSCLC NOS; it should be considered in individuals with squamous cell carcinoma with small biopsy specimens or mixed histology.
KRAS point mutations.
Like BRAF, sequencing methods are used in the identification of point mutations within the KRAS gene. For NSCLC, the most common KRAS mutations are located in codon 12 even though other point mutations may occur elsewhere. KRAS mutations have been linked as a prognostic indicator of poor survival and can impact EGFR TKI therapy. The NCCN states, “KRAS mutations do not generally overlap with “EGFR, , ROS1, BRAF, and ALK genetic variants. Therefore, a tiered approach using KRAS testing may identify patients who may not benefit from further molecular biomarker testing. A newly designed oral KRAS G12C inhibitor was found to be effective in use against the KRAS p.G12C mutation, but this class of inhibitor has not been evaluated for any other mutations.
MET exon 14 skipping variants.
NGS-based testing, particularly RNA-based as it provides improved detection, is used to detect METex14 skipping events. Immunohistochemistry is not used. Oral TKI therapy is used to address a METex14 skipping mutation when detected. The NCCN states that “NGS-based testing is the primary method for detection of METex14 skipping events; RNA-based NGS may have improved detection. IHC is not a method for detection of METex14 skipping.”
RET
FISH break-apart probe methodology is one appropriate method used to detect a RET mutation, though it may under-detect some fusions. NCCN also states that “Targeted real-time reverse-transcriptase PCR assays are utilized in some settings, although they are unlikely to detect fusions with novel partners. NGS-based methodology has a high specificity, and RNA-based NGS is preferable to DNA-based NGS for fusion detection.” Sequencing methods such as NGS and rtPCR are effective but rtPCR has difficulty detecting fusions with novel partners. RNA-based NGS has better fusion detection capability than DNA-based NGS. Regardless of fusion partner, RET mutations are responsive to oral RET TKI therapies.
ERRB2
The ERBB2 gene encodes for HER2. ERBB2 mutations, amplifications, and alterations, have been identified in various tumor types. NCCN states “While targeted PCR techniques can be utilized to examine ERBB2 mutations, the diversity and spectrum of mutations are best surveyed using NGS-based approaches.” Additionally, “At this time, there is no recommendation regarding specific IHC antibody clone for HER2 staining in NSCLC.”
NTRK gene fusion
The NCCN has an NTRK gene fusion positive algorithm where larotrectinib is to be used as a first-line therapy if the gene fusion was discovered prior to first-line systemic therapy. If the NTRK gene fusion was discovered during a different first-line systemic therapy, then they recommend completing the planned systemic therapy, including maintenance therapy, and then follow this first-line therapy up with larotrectinib. As a category 2A recommendation, the NCCN recommends NTRKgene fusion testing to be included as part of molecular profiling for all forms of advanced or metastatic disease, including adenocarcinoma, large cell, NSCLC NOS, and squamous cell carcinoma. “The NCCN NSCLC Panel recommends larotrectinib and entrectinib (both are category 2A) as either first-line or subsequent therapy options for patients with NTRK gene fusion-positive metastatic NSCLC based on data and the FDA approvals. As of the v3 2020 update, both agents are considered “preferred” first-line therapies for patients with NTRK gene fusion-positive metastatic disease.
PD-L1
PD-L1 is expressed on tumor cells; its presence is used to determine possible pembrolizumab therapy. The FDA has approved IHC use for assessing PD-L1. The FDA-approved companion diagnostic for PD-L1 guides utilization of pembrolizumab in patients with NSCLC and is based on the tumor proportion score. As a category 1 recommendation, PD-L1 testing is recommended for all cases of advanced or metastatic disease, including adenocarcinoma, large cell, NSCLC NOS, and squamous cell carcinoma. NCCN states that, in comparison to TMB, “PD-L1 expression level is a more useful immune biomarker than TMB for deciding how to use immunotherapy, because test results are obtained more quickly, less tissue is needed for testing, and data demonstrate relative reproducibility across platforms and individuals.” However, “While some clones for PD-L1 IHC are FDA-approved for specific indications, use of multiple IHC tests is not necessary, provided any individual IHC test has been internally validated for comparability for categorical results against the FDA-approved clone.”
Tumor Mutational Burden (TMB)
NCCN reports that “In 2020, the NCCN Panel deleted tumor mutational burden (TMB) as an emerging immune biomarker based on clinical trial data and other issues.” Preliminary data from PFS from CHECKMATE 227, a phase 3 randomized trial with a complex design, had suggested that TMB might be a useful immune biomarker for deciding whether to use immunotherapy in patients with metastatic NSCLC, but updated data indicated that “overall survival was improved with nivolumab plus ipilimumab regardless of TMB or PD-L1 expression levels”. Furthermore, “Several trials have shown that high TMB levels do not correlate with PD-L1 expression levels in patients with NSCLC”. This lack of clinical data, coupled with technical problems with measuring TMB—including “: 1) lack of agreement on the definition of a cut off for designating high TMB levels; and 2) lack of standardization of TMB measurements across laboratories”—drives the NCCN Guidelines to “not recommend measurement of TMB levels before deciding whether to use nivolumab plus ipilimumab regimens or to use other ICIs, such as pembrolizumab.”
Emerging biomarkers to identify novel therapies.
The NCCN lists the following emerging biomarkers to identify novel therapies for patients with metastatic NSCLC.