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 anEGFR-sensitive mutation andYES1amplification 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 thatYES1amplification might be associated with primary resistance to EGFR-TKIs andYES1amplification might be a negative predictor of EGFR-TKI treatment in NSCLC patients harboringEGFRsensitive mutations.