EGFR and lung adenocarcinoma: This study was performed to investigate the detection rate of EGFR T790M mutation by repeated rebiopsy, to identify the clinical factors related to repeated rebiopsy, and to assess survival outcomes according to the methods and numbers of repeated rebiopsies in patients with lung adenocarcinoma who received sequential osimertinib after failure of previous 1st or 2nd generation EGFR-tyrosine kinase inhibitors.