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a change in amino acid residue at position 263 of the epidermal growth factor receptor protein, where L-threonine has been replaced by L-proline.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.