Efficacy of pembrolizumab for patients with both high PD-L1 expression and an MET exon 14 skipping mutation: A case report.

Pembrolizumab has become the standard first-line treatment for non-small cell lung cancer (NSCLC) patients with high PD-L1expression. MET exon 14 skipping is a rare mutation typically found in older, female, and non-smoking patients with NSCLC. Herein, we report the case of a 71-year-old non-smoking woman who was diagnosed with NSCLC in the left lung. EGFR mutation and ALK fusion were not detected. Because the biopsy specimen showed high PD-L1 expression with a tumor proportion score of 95%, pembrolizumab was introduced as first-line therapy, but resulted in no clinical benefit. The patient was subsequently administered chemotherapy with carboplatin and pemetrexed, leading to remarkable tumor shrinkage. A next-generation sequencing panel analysis revealed a MET exon 14 skipping mutation. Thus, pembrolizumab might not be effective for NSCLC patients with MET exon 14 skipping mutations, even if PD-L1 expression is high.