PD‐L1‐negative non‐small cell lung cancer harbouring a rare BRAF mutation with successful treatment of first‐line pembrolizumab plus chemotherapy: A case report and review the literature

BRAF mutations are uncommon in non‐small cell lung cancer (NSCLC), accounting for less than 5% of all NSCLC cases. The utilization of targeted therapies in non‐V600E BRAF mutant NSCLC is considered controversial, although non‐V600E genotype is reported in ~50% of all BRAF mutant patients. We document the case of a 63‐year‐old patient with NSCLC harbouring a rare BRAF E501Q mutation, who had prolonged response to immunotherapy combined with chemotherapy in Vietnam. The patient was diagnosed with metastatic PD‐L1‐negative lung adenocarcinoma and received pembrolizumab plus chemotherapy as first‐line treatment. After completing 35 cycles of pembrolizumab and pemetrexed, his disease has remained stable during the treatment‐free follow‐up period, and he is alive 38 months after treatment initiation at the latest follow‐up. Immune‐based therapy is an appropriate option for lung adenocarcinoma with rare non‐V600E BRAF mutation. Further clinical studies are necessary to determine the effectiveness of using immune‐based therapy in this specific population.