EGFR and lung adenocarcinoma: These 2 mutations account for 85% to 90% of EGFR mutations.5–8 TKIs, which bind to the tyrosine kinase domain of EGFR,7 have demonstrated clinical efficacy for the treatment of advanced lung adenocarcinoma.9,10 Lesions with Ex19 and Ex21 mutations are thought to exhibit different clinical behavior, and some previous reports demonstrated that Ex19 lesions responded better to EGFR-TKIs and platinum-based chemotherapy than Ex21 lesions in a population with unresectable lung cancer.10–14