We enrolled 421 patients with stage IV lung adenocarcinoma and sensitizing EGFR mutations receiving an EGFR-TKI as their first-line therapy, including first-generation (1st G, gefitinib and erlotinib), second-generation (2nd G, afatinib), and third-generation (3rd G, osimertinib) EGFR TKIs. Here, EGFR is linked to lung adenocarcinoma.