Rare T263P epidermal growth factor receptor extracellular domain mutation of advanced non‐small cell lung cancer in a Vietnamese male patient

T263P mutation is one of the rare EGFR mutations located on chromosome 7p11.2, which is a change in amino acid residue at position 263 of the epidermal growth factor receptor protein, where L‐threonine has been replaced by L‐proline. This missense mutation in the extracellular EGFR domain is not well‐known in lung cancer. In this study, we first report a patient with advanced lung adenocarcinoma harbouring only a rare T263P EGFR mutation who benefited from first‐line afatinib therapy in Vietnam. The patient achieved a partial response with a time‐to‐treatment failure of 5 months. The patient subsequently received several chemotherapy regimens as the disease progressed, with overall survival of 17 months. Non‐small cell lung cancer with a rare T263P EGFR mutation responds to afatinib but has a poor prognosis. Further studies are needed to determine the efficacy of targeted therapies in this specific population.