Role of YES1 amplification in EGFR mutation‐positive non‐small cell lung cancer: Primary resistance to afatinib in a patient

Epidermal growth factor receptor (EGFR) mutation‐positive non‐small cell lung cancer (NSCLC) patients benefit from EGFR tyrosine kinase inhibitors (TKIs), while some patients demonstrate a resistance to EGFR‐TKIs. In the case reported here, the NSCLC patient harboring an EGFR‐sensitive mutation and YES1 amplification was treated with afatinib as first‐line therapy, but was found to have progressive disease four weeks later. During subsequent chemotherapy, this patient's disease progressed rapidly. Mechanisms of primary resistance to EGFR‐TKIs remain unclear. This case suggested that YES1 amplification might be associated with primary resistance to EGFR‐TKIs and YES1 amplification might be a negative predictor of EGFR‐TKI treatment in NSCLC patients harboring EGFR sensitive mutations.