Non-small cell lung cancer with MET exon 14 skipping alteration responding to immunotherapy: a case report

Immunotherapy has been proved to be a promising candidate for advanced non-small cell lung cancer (NSCLC). Despite MET mutations are regarded as an independent factor of programmed death ligand 1 (PD-L1) high expression, the efficacy of immune checkpoint inhibitors (ICIs) across NSCLC harboring Mesenchymal-epithelial transition factor exon 14 skipping alteration (METex14) is still uncleared. Moreover, when the resistance of PD-1 antibody occurs, the questions of how to interpret the resistance and how to overcome the resistance are worth exploring. We report a case of NSCLC with METex14 developed a right femoral metastasis after responding well to neoadjuvant immunotherapy, a successful lobectomy, and adjuvant immunotherapy. The subsequent attempts of MET targeted inhibitor, concurrent chemoradiotherapy, and notably programmed cell death protein 1 (PD-1) antibody plus vascular endothelial growth factor receptor tyrosine kinase inhibitor (VEGFR-TKI) failed to prevent disease progression. However, a regimen of anti-PD-1 plus anti-cytotoxic t-lymphocyte associated protein 4 (CTLA-4) reversed the progression to a complete response. This case shows that METex14 had a significant response to immunotherapy, which would be especially beneficial for those who developed targeted therapy resistance. Importantly, this is the first case reporting that salvage CTLA-4 antibody and PD-1 antibody could reverse the progression in NSCLC harboring METex14 when the anti-PD-1 resistance occurred.