MET Exon 14 Skipping in NSCLC: A Systematic Literature Review of Epidemiology,Clinical Characteristics,and Outcomes

IntroductionMET exon 14 (METex14) skipping is a rare oncogenic driver in non–small-cell lung cancer (NSCLC) for which targeted therapy with MET tyrosine kinase inhibitors (TKIs) was recently approved. Given the heterogeneity in published data of METex14 skipping NSCLC, we conducted a systematic literature review to evaluate its frequency, patient characteristics, and outcomes.MethodsOn June 13, 2022 we conducted a systematic literature review of publications and conference abstracts reporting frequency, patient characteristics, or outcomes of patients with METex14 skipping NSCLC.ResultsWe included 139 studies reporting frequency or patient characteristics (350,997 patients), and 39 studies reporting clinical outcomes (3989 patients). Median METex14 skipping frequency was 2.0% in unselected patients with NSCLC, with minimal geographic variation. Median frequency was 2.4% in adenocarcinoma or nonsquamous subgroups, 12.0% in sarcomatoid, and 1.3% in squamous histology. Patients with METex14 skipping NSCLC were more likely to be elderly, have adenocarcinoma histology; there was no marked sex or smoking status distribution. In first line of treatment, median objective response rate ranged from 50.7% to 68.8% with targeted therapies (both values correspond to MET TKIs), was 33.3% with immunotherapy, and ranged from 23.1% to 27.0% with chemotherapy.ConclusionsPatients with METex14 skipping are more likely to have certain characteristics, but no patient subgroup can be ruled out; thus, it is crucial to test all patients with NSCLC to identify suitable candidates for MET inhibitor therapy. MET TKIs appeared to result in higher efficacy outcomes, although no direct comparison with chemotherapy or immunotherapy regimens was found.     

Safety of MET Tyrosine Kinase Inhibitors in Patients With MET Exon 14 Skipping Non-small Cell Lung Cancer: A Clinical Review

MET exon 14 (METex14) skipping mutations occur in 3% to 4% of non-small cell lung cancer (NSCLC) cases. Currently, four oral MET tyrosine kinase inhibitors (TKIs) are in use for the treatment of patients with METex14 skipping NSCLC (tepotinib, capmatinib, savolitinib, and crizotinib). To support optimal management of METex14 skipping NSCLC in this typically older patient population, the safety profiles of these treatment options are reviewed here. Published safety data from prospective clinical trials with MET TKIs in patients with METex14 skipping NSCLC were reviewed. Treatment-related adverse events (TRAEs) occurring in ≥ 10% of patients were reported where feasible. Guidance on clinical monitoring and management of key MET TKI TRAEs and drug-drug interactions is provided. Across the clinical trials, safety data for MET TKIs were reported for 442 patients with METex14 skipping. Peripheral edema was the most reported TRAE (50%-63% of patients; grade ≥ 3: 1%-11%), followed by nausea (26%-46% of patients; grade ≥ 3: 0%-1%). TRAEs led to dose reductions in 33% to 38% of patients and to discontinuation in 7% to 14% of patients, across the MET TKIs. Considerations on interpreting available safety data are provided, along with insights into monitoring and managing specific MET TKI TRAEs of interest and drug-drug interactions. Overall, MET TKIs are tolerable treatment options for patients with METex14 skipping NSCLC, an older population for whom chemo- or immuno-therapy may not be an effective nor tolerable option. More data regarding the effectiveness of safety interventions and management strategies are needed.     

Emergence of Preexisting MET Y1230C Mutation as a Resistance Mechanism to Crizotinib in NSCLC with MET Exon 14 Skipping

IntroductionMET proto-oncogene, receptor tyrosine kinase gene exon 14 skipping (METex14) alterations represent a unique subset of oncogenic drivers in NSCLC. Preliminary clinical activity of crizotinib against METex14-positive NSCLC has been reported. The full spectrum of resistance mechanisms to crizotinib in METex14-positive NSCLC remains to be identified.MethodsHybrid capture–based comprehensive genomic profiling performed on a tumor specimen obtained at diagnosis, and a hybrid capture–based assay of circulating tumor DNA (ctDNA) at the time of progression during crizotinib treatment was assessed in a pairwise fashion.ResultsA METex14 alteration (D1010H) was detected in the pretreatment tumor biopsy specimen, as was MET proto-oncogene, receptor tyrosine kinase (MET) Y1230C, retrospectively, at very low frequency (0.3%). After a confirmed response during crizotinib treatment for 13 months followed by progression, both MET proto-oncogene, receptor tyrosine kinase gene Y1230C and D1010H were detected prospectively in the ctDNA.ConclusionEmergence of the preexisting MET Y1230C likely confers resistance to crizotinib in this case of METex14-positive NSCLC. Existence of pretreatment MET Y1230C may eventually modulate the response of METex14-positive NSCLC to type I MET tyrosine kinase inhibitors. Noninvasive plasma-based ctDNA assays can provide a convenient method to detect resistance mutations in patients with previously known driver mutations.     

MET IHC Is a Poor Screen for MET Amplification or MET Exon 14 Mutations in Lung Adenocarcinomas: Data from a Tri-Institutional Cohort of the Lung Cancer Mutation Consortium

IntroductionMNNG HOS Transforming gene (MET) amplification and MET exon 14 (METex14) alterations in lung cancers affect sensitivity to MET proto-oncogene, receptor tyrosine kinase (MET [also known by the alias hepatocyte growth factor receptor]) inhibitors. Fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) have been used to evaluate MET dependency. Here, we have determined the association of MET IHC with METex14 mutations and MET amplification.MethodsWe collected data on a tri-institutional cohort from the Lung Cancer Mutation Consortium. All patients had metastatic lung adenocarcinomas and no prior targeted therapies. MET IHC positivity was defined by an H-score of 200 or higher using SP44 antibody. MET amplification was defined by copy number fold change of 1.8x or more with use of NGS or a MET-to–centromere of chromosome 7 ratio greater than 2.2 with use of FISH.ResultsWe tested tissue from 181 patients for MET IHC, MET amplification, and METex14 mutations. Overall, 71 of 181 patients (39%) were MET IHC–positive, three of 181 (2%) were MET-amplified, and two of 181 (1%) harbored METex14 mutations. Of the MET-amplified cases, two were FISH positive with MET-to–centromere of chromosome 7 ratios of 3.1 and 3.3, one case was NGS positive with a fold change of 4.4x, and one of the three cases was MET IHC–positive. Of the 71 IHC-positive cases, one (1%) was MET-amplified and two (3%) were METex14-mutated. Of the MET IHC–negative cases, two of 110 (2%) were MET-amplified.ConclusionsIn this study, nearly all MET IHC–positive cases were negative for MET amplification or METex14 mutations. MET IHC can also miss patients with MET amplification. The limited number of MET-amplified cases in this cohort makes it challenging to demonstrate an association between MET IHC and MET amplification. Nevertheless, IHC appears to be an inefficient screen for these genomic changes. MET amplification or METex14 mutations can best be detected by FISH and a multiplex NGS panel.     

Safety of Tepotinib in Patients With MET Exon 14 Skipping NSCLC and Recommendations for Management

IntroductionThe MET inhibitor tepotinib demonstrated durable clinical activity in patients with advanced MET exon 14 (METex14) skipping NSCLC. We report detailed analyses of adverse events of clinical interest (AECIs) in VISION, including edema, a class effect of MET inhibitors.Patients and MethodsIncidence, management, and time to first onset/resolution were analyzed for all-cause AECIs, according to composite categories (edema, hypoalbuminemia, creatinine increase, and ALT/AST increase) or individual preferred terms (pleural effusion, nausea, diarrhea, and vomiting), for patients with METex14 skipping NSCLC in the phase II VISION trial.ResultsOf 255 patients analyzed (median age: 72 years), edema, the most common AECI, was reported in 69.8% (grade 3, 9.4%; grade 4, 0%). Median time to first edema onset was 7.9 weeks (range: 0.1-58.3). Edema was manageable with supportive measures, dose reduction (18.8%), and/or treatment interruption (23.1%), and rarely prompted discontinuation (4.3%). Other AECIs were also manageable and predominantly mild/moderate: hypoalbuminemia, 23.9% (grade 3, 5.5%); pleural effusion, 13.3% (grade ≥ 3, 5.1%); creatinine increase, 25.9% (grade 3, 0.4%); nausea, 26.7% (grade 3, 0.8%), diarrhea, 26.3% (grade 3, 0.4%), vomiting 12.9% (grade 3, 1.2%), and ALT/AST increase, 12.2% (grade ≥ 3, 3.1%). GI AEs typically occurred early and resolved in the first weeks.ConclusionTepotinib was well tolerated in the largest trial of a MET inhibitor in METex14 skipping NSCLC. The most frequent AEs were largely mild/moderate and manageable with supportive measures and/or dose reduction/interruption, and caused few withdrawals in this elderly population.     

High MET Overexpression Does Not Predict the presence of MET exon 14 Splice Mutations in NSCLC: Results From the IFCT PREDICT.amm study

IntroductionMET proto-oncogene (MET) exon 14 splice site (METex14) mutations were recently described in NSCLC and has been reported to correlate with efficacy of MET tyrosine kinase inhibitors. High diversity of these alterations makes them hard to detect by DNA sequencing in clinical practice. Because METex14 mutations induce increased stabilization of the MET receptor, it is anticipated that these mutations are associated with MET overexpression. We aim to determine whether NSCLC with high MET overexpression could define a subset of patients with a high rate of METex14 mutations.MethodsFrom The French Cooperative Thoracic Intergroup PREDICT.amm cohort of 843 consecutive patients with a treatment-naive advanced NSCLC who were eligible for a first-line therapy, 108 NSCLC samples with high MET overexpression defined by an immunochemistry score 3+ were tested for METex14 mutations using fragment length analysis combined with optimized targeted next-generation sequencing. MET copy number analysis was also derived from the sequencing data.ResultsMETex14 mutations were detected in two patients (2.2%) who also displayed a TP53 mutation and a PIK3CA mutation, respectively. An MET gene copy number increase was observed in seven additional patients (7.7%). Next-generation sequencing analysis revealed inactivating mutations in TP53 (52.7%) and PTEN (1.1%), and oncogenic mutations in KRAS (28.6%), EGFR (7.7%), PIK3CA (4.4%), BRAF (4.4%), NRAS (2.2%), GNAS (1.1%), and IDH1 (1.1%).ConclusionsThe rate of METex14 mutations in NSCLC with high MET overexpression was similar to that found in unselected NSCLC. Moreover, we observed a high frequency of driver alterations in other oncogenes. Consequently these findings do not support the use of MET immunohistochemistry as a surrogate marker for METex14 mutations.     

Intra-tumor and Inter-tumor Heterogeneity in MET Exon 14 Skipping Mutations and Co-mutations in Pulmonary Pleomorphic Carcinomas

BackgroundMET exon 14 skipping mutation is a driver mutation in lung cancer and is highly enriched in pulmonary pleomorphic carcinomas (PPCs). Whether there is intratumor or intertumor heterogeneity in MET exon 14 skipping status or in co-occurring genetic alterations in lung cancers driven by MET exon 14 skipping is unknown.MethodsWe analyzed tumor specimens obtained from 23 PPC patients (10 autopsied and 13 surgically resected). MET exon 14 skipping was detected by RT-PCR. For patients with MET exon 14 skipping mutation, further analyses were performed. Genomic DNA (gDNA) was extracted from various histological components for each patient who underwent surgical resection (to assess intratumor heterogeneity). In autopsied patients, gDNA and total RNA were extracted from all metastatic lesions (to assess intertumor heterogeneity).ResultsMET exon 14 skipping mutation was detected in 4 patients (4/23, 17.4%): two surgically resected and two autopsied patients. We found no intratumor or intertumor heterogeneity in MET exon 14 skipping mutation status in these patients. We observed intratumor and intertumor heterogeneity in the copy number variations and/or mutational status of cancer-related genes; some of these differences may have an impact on MET tyrosine kinase inhibitor (TKI) efficacy.ConclusionIn our exploratory analysis of four cases, we observed that MET exon 14 skipping mutations are distributed homogeneously throughout histological components and between metastatic lesions. Our results also suggest that there is marked intertumor and intratumor heterogeneity in co-occurring genetic alterations, and therapeutic implications of such heterogeneity should be evaluated in future studies.     

A Phase 2 Study of Capmatinib in Patients With MET-Altered Lung Cancer Previously Treated With a MET Inhibitor

IntroductionCapmatinib is approved for MET exon 14–altered NSCLC on the basis of activity in targeted therapy–naive patients. We conducted a phase 2 study to assess the efficacy of capmatinib in patients previously treated with a MET inhibitor.MethodsPatients with advanced NSCLC harboring MET amplification or MET exon 14 skipping alterations received capmatinib 400 mg twice daily. The primary end point was the objective response rate. Secondary end points included progression-free survival, disease control rate (DCR), intracranial response rate, and overall survival. Circulating tumor DNA was analyzed to identify capmatinib resistance mechanisms.ResultsA total of 20 patients were enrolled between May 2016 and November 2019, including 15 patients with MET skipping alterations and five patients with MET amplification. All patients had received crizotinib; three had also received other MET-directed therapies. The median interval between crizotinib and capmatinib was 22 days (range: 4–374). Two patients (10%) achieved an objective response to capmatinib and 14 had stable disease, yielding a DCR of 80%. Among five patients who discontinued crizotinib for intolerance, the DCR was 83%, including two patients with the best tumor shrinkage of −25% and −28%. Intracranial DCR among four patients with measurable brain metastases was 100%, with no observed intracranial objective responses. Overall, the median progression-free survival and overall survival were 5.5 (95% confidence interval: 1.3–11.0) and 11.3 (95% confidence interval: 5.5–not reached) months, respectively. MET D1228 and Y1230 mutations and MAPK alterations were recurrently detected in postcrizotinib, precapmatinib plasma. New and persistent MET mutations and MAPK pathway alterations were detected in plasma at progression on capmatinib.ConclusionsCapmatinib has modest activity in crizotinib-pretreated MET-altered NSCLC, potentially owing to overlapping resistance mechanisms.     

MET Exon 14 Alterations and New Resistance Mutations to Tyrosine Kinase Inhibitors: Risk of Inadequate Detection with Current Amplicon-Based NGS Panels

IntroductionTargeted therapies such as tyrosine kinase inhibitors (TKIs) have dramatically improved the treatment of lung adenocarcinoma, and detection of activating mutations of genes such as EGFR or anaplastic lymphoma kinase gene (ALK) is now mandatory in the clinical setting. However, additional targetable alterations are continuously being described and forcing us to adapt our detection methods. Here we have evaluated the ability of eight amplicon-based next-generation sequencing (NGS) panels to detect the recently described mesenchymal epithelial transition factor (MET) exon 14 (METex14) alterations or new mutations conferring resistance to TKIs.MethodsA total of 191 tumor samples from patients with NSCLC were screened for METex14 mutations by Sanger sequencing, and 62 additional cases were screened by Sanger sequencing and two amplicon-based NGS panels. In silico comparison of eight commercially available targeted NGS panels was also performed for the detection of METex14 alterations or ALK, ROS1, or EGFR resistance mutations.ResultsNGS analysis of the positive METex14 cases revealed a false-negative case because of amplicon design. Moreover, in silico analysis revealed that none of the eight panels considered would be able to detect more than 63% of literature-reported cases of METex14 mutations and similar limitations would be expected with new ALK, ROS1, or EGFR resistance mutations.ConclusionsWe have illustrated major limitations of commercially available amplicon-based DNA NGS panels for detection of METex14 and recently described resistance mutations to TKIs. Documented choice of available panels and their frequent reevaluation are mandatory to deliver the most accurate data to the clinician for therapeutic decisions.     

Asian Thoracic Oncology Research Group (ATORG) Expert Consensus Statement on MET Alterations in NSCLC: Diagnostic and Therapeutic Considerations

Non-small cell lung cancer (NSCLC) is a heterogeneous disease, with many oncogenic driver mutations, including de novo mutations in the Mesenchymal Epithelial Transition (MET) gene (specifically in Exon 14 [ex14]), that lead to tumourigenesis. Acquired alterations in the MET gene, specifically MET amplification is also associated with the development of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) resistance in patients with EGFR-mutant NSCLC. Although MET has become an actionable biomarker with the availability of MET-specific inhibitors in selected countries, there is differential accessibility to diagnostic platforms and targeted therapies across countries in Asia-Pacific (APAC).The Asian Thoracic Oncology Research Group (ATORG), an interdisciplinary group of experts from Australia, Hong Kong, Japan, Korea, Mainland China, Malaysia, the Philippines, Singapore, Taiwan, Thailand and Vietnam, discussed testing for MET alterations and considerations for using MET-specific inhibitors at a consensus meeting in January 2022, and in subsequent offline consultation.Consensus recommendations are provided by the ATORG group to address the unmet need for standardised approaches to diagnosing MET alterations in NSCLC and for using these therapies. MET inhibitors may be considered for first-line or second or subsequent lines of treatment for patients with advanced and metastatic NSCLC harbouring MET ex14 skipping mutations; MET ex14 testing is preferred within multi-gene panels for detecting targetable driver mutations in NSCLC. For patients with EGFR-mutant NSCLC and MET amplification leading to EGFR TKI resistance, enrolment in combination trials of EGFR TKIs and MET inhibitors is encouraged.     

Capmatinib in Japanese patients with MET exon 14 skipping–mutated or MET-amplified advanced NSCLC: GEOMETRY mono-1 study

MET mutations leading to exon 14 skipping (METΔex14) are strong molecular drivers for non–small-cell lung cancer (NSCLC). Capmatinib is a highly potent, selective oral MET inhibitor that showed clinically meaningful efficacy and a manageable safety profile in a global phase II study (GEOMETRY mono-1, NCT02414139) in patients with advanced METΔex14-mutated/MET-amplified NSCLC. We report results of preplanned analyses of 45 Japanese patients according to MET status (METΔex14-mutated or MET-amplified) and line of therapy (first- [1L] or second-/third-line [2/3L]). The starting dose was 400 mg twice daily. The primary endpoint was the objective response rate (ORR) assessed by a blinded independent review committee. A key secondary endpoint was duration of response (DOR). Among METΔex14-mutated patients, in the 1L group, one patient achieved partial response (DOR of 4.24 months) and the other had stable disease. In the 2/3L group, the ORR was 36.4% (95% confidence interval [CI] 10.9%-69.2%), median DOR was not evaluable, and progression-free survival was 4.70 months. One patient (2/3L group) showed partial resolution of brain lesions per independent neuroradiologist review. In MET-amplified patients with a MET gene copy number of ≥10, the ORR was 100% (2/2 patients) in the 1L group and 45.5% (5/11 patients) in the 2/3L group, with DOR of 8.2 and 8.3 months, respectively. Common treatment-related adverse events among the 45 Japanese patients were blood creatinine increased (53.3%), nausea (35.6%), and oedema peripheral (31.1%); most were grade 1/2 severity. In conclusion, capmatinib was effective and well tolerated by Japanese patients with METΔex14/MET-amplified NSCLC, consistent with the overall population.     

MET Amplification (MET/CEP7 Ratio ≥ 1.8) Is an Independent Poor Prognostic Marker in Patients With Treatment-naive Non–Small-cell Lung Cancer

IntroductionThe MET pathway is a promising target in patients with non–small-cell lung cancer (NSCLC). Fluorescence in situ hybridization analysis has become a standard method to detect MET amplification. However, no consensus has been reached regarding the definition of MET amplification. We aimed to find clinically meaningful cutoffs for MET amplification that could be used as a prognostic marker and/or indication for MET inhibitor therapy.Patients and MethodsWe reviewed the fluorescence in situ hybridization results of MET/CEP7 (centromere of chromosome 7) for 2260 patients with treatment-naive NSCLC from 2014 to 2019. Clinical and pathologic data were collected from the medical records. Log-rank tests and Cox proportional hazard models were used to estimate the overall survival (OS) among patients with different MET/CEP7 ratios and/or MET copy numbers.ResultsOf the 2260 patients, 130 (5.8%) had had a MET/CEP7 ratio of ≥ 1.8 and 13 (0.6%) had had a ratio of ≥ 5.0. Of these 130 patients with a MET/CEP7 ratio of ≥ 1.8, 123 (95%) also had a MET copy number of ≥ 5. In general, a higher MET copy number and higher MET/CEP7 ratio were associated with advanced tumor stage. The OS was significantly shorter when the MET copy number was ≥ 10 and/or when the MET/CEP7 ratio was ≥ 1.8. A MET/CEP7 ratio of ≥ 1.8 remained a significant hazard to OS on multivariate analysis (hazard ratio, 1.63; P = .019).ConclusionsPatients with a MET copy number of ≥ 10 and/or MET/CEP7 ratio of ≥ 1.8 showed significantly poorer survival, and a MET/CEP7 ratio of ≥ 1.8 was an independent poor prognostic factor.     

A Higher Proportion of the EGFR T790M Mutation May Contribute to the Better Survival of Patients with Exon 19 Deletions Compared with Those with L858R

IntroductionIncreasing evidence has demonstrated that exon 19 deletions (Del19) and L858R mutation in EGFR have different prognostic and predictive roles in NSCLC. We aimed to investigate whether these two mutations produced differences in mechanisms of resistance to EGFR tyrosine kinase inhibitors.MethodsConsecutive patients with advanced EGFR-mutant NSCLC who acquired resistance to EGFR tyrosine kinase inhibitors and underwent postprogression biopsy were enrolled. Mechanisms including T790M mutation, mesenchymal-epithelial transition proto-oncogene (MET) amplification, and histological transformation, as well as KRAS, phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha gene (PIK3CA) mutation, and anaplastic lymphoma receptor tyrosine kinase gene (ALK) fusion, were analyzed.ResultsThe prevalence of T790M mutation was significantly higher in the Del19 subgroup than that in L858R subgroup (50.4% versus 36.5%, p = 0.043). Apart from this, there was no difference in other mechanisms including MET amplification and histological transformation. The median overall survival (OS) of patients with T790M mutation was 36.0 months (95% confidence interval [CI]: 30.9–41.2), which was significantly longer than the 26.5 months (95% CI: 24.0–29.0) in MET-positive patients, 19.7 months (95% CI: 18.2–21.2) in patients with histological transformation, and 23.0 months (95% CI: 17.4–28.6) in the KRAS/PIK3CA/ALK-altered population (p = 0.021). The hazard ratios of the MET-amplification subgroup and subgroup with histological transformation were 1.809-fold and 2.370-fold higher than that in T790M-positive subgroup. The median OS times were months 33.3 (95% CI: 28.9–37.7) in the Del19 subgroup and 26.4 months (95% CI: 23.2–29.6) in the L858R subgroup (p = 0.028). However, in multivariable analysis adjusted for T790M genotype, the EGFR mutation subtype was no longer found to be significant.ConclusionsSignificant OS benefit was observed in patients with T790M mutation, suggesting that a larger proportion of T790M mutation might contribute to the better survival of patients with Del19.     

MET Expression in Advanced Non–Small-Cell Lung Cancer: Effect on Clinical Outcomes of Chemotherapy,Targeted Therapy,and Immunotherapy

Background

The receptor tyrosine kinase MET is implicated in malignant transformation, tumor progression, metastasis, and acquired treatment resistance. We conducted an analysis of the effect of MET expression and MET genomic aberrations on the outcome of patients with advanced or metastatic pulmonary adenocarcinomas prospectively enrolled in an institutional precision oncology program.

The promise of selective MET inhibitors in non-small cell lung cancer with MET exon 14 skipping

Dysregulated activation of the MET tyrosine kinase receptor is implicated in the development of solid tumors and can arise through several mechanisms, including gene amplification, overexpression of the receptor and/or its ligand hepatocyte growth factor (HGF), and the acquisition of activating mutations. The most common activating mutations cause exon 14 to be skipped during MET mRNA splicing. This in-frame deletion, known as MET exon 14, results in production of a shortened receptor that lacks a juxtamembrane domain but retains affinity for HGF. However, the negative regulatory function located within this protein sequence is lost, leading to receptor accumulation on the cell surface and prolonged activation by HGF. MET mutations causing exon 14 skipping appear to be true oncogenic drivers and occur in patients and tumors with distinct characteristics.Increasing evidence suggests that tumors carrying such mutations are sensitive to MET inhibition, raising the hope that selective MET inhibitors will provide patients with optimal anticancer activity with minimal toxicity.We discuss the prospects for selective MET inhibitors in the treatment of non-small cell lung cancer harboring MET exon 14 skipping.     

Oncogene Overlap Analysis of Circulating Cell-free Tumor DNA to Explore the Appropriate Criteria for Defining MET Copy Number–Driven Lung Cancer

IntroductionDefining clinically relevant MET amplification levels in non-small cell lung cancer (NSCLC) remains challenging. We hypothesize that oncogene overlap and MET amplicon size decline with increase in MET plasma copy number (pCN), thus enriching for MET-dependent states.Patients and MethodsWe interrogated cell-free DNA NGS results of 16,782 patients with newly diagnosed advanced NSCLC to identify those with MET amplification as reported using Guardant360. Co-occurring genomic mutations and copy number alterations within each sample were evaluated. An exploratory method of adjusting for tumor fraction was also performed and amplicon size for MET was analyzed when available.ResultsMET amplification was detected in 207 (1.2%) of samples. pCN ranged from 2.1 to 52.9. Of these, 43 (20.8%) had an overlapping oncogenic driver, including 23 (11.1%) METex14 skipping or other MET mutations. The degree of (non-MET) oncogene overlap decreased with increases in pCN. Patients with MET pCN ≥ 2.7 had lower rates of overlapping drivers compared to those with MET pCN < 2.7 (6.1% vs. 16.3%, P = .033). None of the 7 patients with pCN > 6.7 had an overlapping driver. After adjusting for tumor fraction, adjusted pCN (ApCN) was also lower for those with overlapping drivers than those without (median ApCN 4.9 vs. 7.3, P =.024). There was an inverse relationship between amplicon size and pCN.ConclusionsWe propose that a high MET pCN and/or ApCN, together with the absence of overlapping oncogenic drivers and small MET amplicon size, will enrich for patients most likely to derive benefit from MET targeted therapy.     

Genetic Heterogeneity of MET-Aberrant NSCLC and Its Impact on the Outcome of Immunotherapy

IntroductionRobust data on the outcome of MET-aberrant NSCLC with nontargeted therapies are limited, especially in consideration of the heterogeneity of MET-amplified tumors (METamp).MethodsA total of 337 tumor specimens of patients with MET-altered Union for International Cancer Control stage IIIB/IV NSCLC were analyzed using next-generation sequencing, fluorescence in situ hybridization, and immunohistochemistry. The evaluation focused on the type of MET aberration, co-occurring mutations, programmed death-ligand 1 expression, and overall survival (OS).ResultsMETamp tumors (n = 278) had a high frequency of co-occurring mutations (>80% for all amplification levels), whereas 57.6% of the 59 patients with MET gene and exon 14 (METex14) tumors had no additional mutations. In the METamp tumors, with increasing gene copy number (GCN), the frequency of inactivating TP53 mutations increased (GCN < 4: 58.2%; GCN ≥ 10: 76.5%), whereas the frequency of KRAS mutations decreased (GCN < 4: 43.2%; GCN ≥ 10: 11.8%). A total of 10.1% of all the METamp tumors with a GCN ≥ 10 had a significant worse OS (4.0 mo; 95% CI: 1.9–6.0) compared with the tumors with GCN < 10 (12.0 mo; 95% confidence interval [CI]: 9.4–14.6). In the METamp NSCLC, OS with immune checkpoint inhibitor (ICI) therapy was significantly better compared with chemotherapy with 19.0 months (95% CI: 15.8–22.2) versus 8.0 months (95% CI: 5.8–10.2, p < 0.0001). No significant difference in median OS was found between ICI therapy and chemotherapy in the patients with METex14 (p = 0.147).ConclusionsMETex14, METamp GCN ≥ 10, and METamp GCN < 10 represent the subgroups of MET-dysregulated NSCLC with distinct molecular and clinical features. The patients with METex14 do not seem to benefit from immunotherapy in contrast to the patients with METamp, which is of particular relevance for the prognostically poor METamp GCN ≥ 10 subgroup.     

Tracking MET de-addiction in lung cancer: A road towards the oncogenic target

The discovery of druggable oncogenic drivers (i.e. EGFR and ALK), along with the introduction of comprehensive tumor genotyping techniques into the daily clinical practice define non-small-cell lung cancer (NSCLC) as a group of heterogeneous diseases, requiring a context-personalized clinico-therapeutical approach. Among the most investigated biomarkers, the MET proto-oncogene has been extensively demonstrated to play a crucial role throughout the lung oncogenesis, unbalancing the proliferation/apoptosis signaling and influencing the epithelial-mesenchymal transition and the invasive phenotype. Nevertheless, although different mechanisms eliciting the aberrant MET-associated oncogenic stimulus have been detected in lung cancer (such as gene amplification, increased gene copy number, mutations and MET/HGF overexpression), to date no clinically impactful results have been achieved with anti-MET tyrosine kinase inhibitors and monoclonal antibodies in the context of an unselected or MET enriched population. Recently, MET exon 14 splicing abnormalities have been identified as a potential oncogenic target in lung cancer, able to drive the activity of MET inhibitors in molecularly selected patients.In this paper, the major advancement and drawbacks of MET history in lung cancer are reviewed, underlying the renewed scientific euphoria related to the recent identification of MET exon 14 splicing variants as an actionable oncogenic target.