At present, only first-generation EGFR-tyrosine kinase inhibitors (TKIs) (erlotinib and gefitinib) are available for clinical use. Second-generation irreversible EGFR-TKIs, such as afatinib, are still in clinical trials. In current clinical practice, EGFR-TKI is the first-line treatment of choice for metastatic NSCLC patients with tumor EGFR mutation or as salvage therapy in NSCLC patients who received systemic chemotherapy previously