Long-term efficacy of immune checkpoint inhibitors in non-small cell lung cancer patients harboring MET exon 14 skipping mutations.

Introduction MET exon 14 skipping mutation, observed in 3-4% of non-small cell lung cancer (NSCLC), is emerging as a targetable alteration. In recent years, immune checkpoint inhibitors (ICI) have been effective in treating several NSCLCs. Our research aimed to investigate the characteristics of patients with NSCLCs harboring MET exon 14 mutations and their response to ICI in Japan. Methods Among the 1954 consecutive NSCLCs diagnosed at Saitama Cancer Center between 2010 and 2019, MET exon 14 skipping mutations were detected in 68 (3.5%) NSCLCs. We evaluated their characteristics such as programmed cell death ligand 1 (PD-L1) expression. Results Median age of patients with NSCLCs harboring MET exon 14 skipping mutations was 73 years. PD-L1 was highly expressed in 17 (70.8%) of the 24 patients examined. Seven patients received ICI monotherapy, and three out of seven had a remarkable treatment response, resulted in objective response rate (ORR) of 42.9% and progression-free survival of 24.7 months. Three patients with donor splice-site mutations showed a long-term treatment response, despite the fact that two with acceptor splice-site mutations demonstrated no response and experienced early disease progression with ICI monotherapy. Conclusion Our results indicated that patients with NSCLCs harboring MET exon 14 mutations presented with a high rate of positive PD-L1 expression. ICI treatment showed a high ORR and long-term efficacy for NSCLCs harboring MET exon 14 mutations. Variants of MET exon 14 splice-site mutations may be associated with ICI response.