Efficacy of Afatinib in a Previously-Treated Patient with Non-Small Cell Lung Cancer Harboring HER2 Mutation: Case Report.

Human epidermal growth factor receptor 2 (HER2) mutation in non-small cell lung cancer (NSCLC) is an oncogenic driver that possibly becomes a druggable target to HER2-targeted therapy. The benefit of HER2-targeted therapy is much less defined especially in eastern populations. We provide evidence of clinical benefit of afatinib in a 50-year-old Asian woman with HER2-mutant NSCLC who previously failed cytotoxic chemotherapy and gefitinib treatment. Next-generation sequencing of the tumor tissue revealed a HER2 exon 20 mutation (c.2437A>G), which has never been reported. The patient was treated with afatinib for more than four months. She showed rapid radiologic response within a month, and maintained stable state until the last dose of afatinib.