Over the past decade, first-line treatment of patients with epidermal growth factor receptor (EGFR) mutation-positive non–small-cell lung cancer (NSCLC) has been revolutionized with the development of first-generation (gefitinib and erlotinib1-6), second-generation (afatinib and dacomitinib7-10), and third-generation (osimertinib11) EGFR tyrosine kinase inhibitors (TKIs). The gene discussed is EGFR; the disease is lung cancer.