Evaluation of different MET genotypes as biomarkers for immunotherapy outcomes in NSCLC patients.

Abstract

e21032 Background: Previous studies suggested that MET exon 14 ( METex14) mutation regarding as a distinct subset was sensitive to MET-inhibitors, but poorly response to immunotherapy. Conversly, MET non-exon-14 (non-ex14) mutations including those undetermined functions and affecting the kinase or extracellular domains were found to be associated with the resistance to MET-inhibitors. However, therapeutic strategies for MET-non-ex14 mutant cancer are still largely unknown, and the relationship between MET-non-ex14 mutations and the efficacy of immune checkpoint inhibitors (ICIs) has never been reported. Using two public ICIs-treated cohorts, we aimed to assess the role of MET mutations including both METex14 and MET-non-ex14 mutations in NSCLC patients undergoing ICIs therapy. Methods: A total of 385 ICIs-treated NSCLC patients were enrolled to our study. MET mutations were defined as any nonsynonymous mutations, and we divided them into METex14 and MET-non-ex14 mutation subsets according to the mutated-position on MET. Kruskal-Wallis test was used to analyze the difference of tumor mutational burden (TMB) score, and the Fisher’s exact test was applied to compare the rates of durable clinical benefit (DCB). Log-rank test was used to analyze the differences between Kaplan-Meier survival curves. Results: In the entire cohort, we found that 17 patients (17/385, 4.4%) had MET mutations, most of which were pure METex14 mutations (10/17, 58.8%). The median TMB of patients in the entire NSCLC cohort was 6.89 mut/Mb. MET-non-ex14 mutant patients (7/385, 1.8%) possessed a significantly higher TMB than METex14-mutant (10/385, 2.6%) and MET wild-type (368/385, 95.6%) sub-cohorts, respectively (median TMB, 17.92 mut/Mb versus 4.17 mut/Mb, p = 0.008; 17.92 mut/Mb versus 6.96 mut/Mb, p = 0.01, respectively). DCB was more common in patients harbored MET-non-ex14 mutations than patients with METex14 mutations and MET wild-type (66.7% versus 14.3%, p = 0.103; 66.7% versus 29.9%, p = 0.075, respectively). We found that patients with MET-non-ex14 mutations had a numerically longer progression free survival (PFS) than those with METex14 mutations and MET wild-type (p = 0.169). Moreover, the PFS was significantly longer in MET-non-ex14-mutant subgroup than patients with METex14 mutations (median PFS, 9.1 versus 2.1 months, p = 0.025). Correspondingly, the overall survival (OS) was significantly longer in MET-non-ex14-mutant subgroup than their wild-type counterparts (median OS, not reached versus 11 months, p = 0.039). Additionally, patients with MET-non-ex14 mutations exhibited relatively better OS versus METex14-mutant patients (median OS, not reached versus 18 months, p = 0.175). Conclusions: MET-non-ex14 mutations were associated with higher TMB, improved DCB rate, and could act as a favorable prognostic biomarker in ICIs-treated NSCLC patients.