After reports of clinical trials1-5 and clinical guidelines (National Institute for Health and Care Excellence [NICE] TA258 and National Comprehensive Cancer Network [NCCN] Non-Small-Cell Lung-17), the use of the tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, is now common practice for first-line treatment of patients with non–small-cell lung cancer (NSCLC) with sensitizing epidermal growth factor receptor (EGFR) mutations. The gene discussed is EGFR; the disease is lung cancer.