Prognostic impacts of EGFR mutation status and subtype in patients with surgically resected lung adenocarcinoma

Objective: Epidermal growth factor receptor (EGFR) gene mutation status is a well-established predictor of the efficacy of EGFR tyrosine-kinase inhibitor (TKI) therapy in patients with non-small cell lung cancer. Recently, differences in EGFR mutation subtypes have been reported to be associated with the efficacy of EGFR-TKI therapy. The prognostic impact of EGFR mutation status and subtypes remains controversial, however. Methods: We retrospectively reviewed 939 patients with surgically resected adenocarcinomas who underwent EGFR mutation status analysis between January 2010 and December 2014. Overall survival (OS) and recurrence-free survival (RFS) were compared according to pathological stage, EGFR mutation status, and EGFR mutation subtype using the log-rank test. Independent prognostic factors for OS and RFS were identified by multivariate analysis using the Cox proportional hazards model. Results: The median duration of follow-up was 48 months. We found that positive EGFR mutation status was significantly associated with longer OS and RFS in all patients and was associated with longer OS in patients in pathological stage I; however, therewere no significant differences inOS and RFS between patients with exon 21 L858Rmutations and those with exon 19 deletions. In a Cox regression model for OS, EGFR mutation status was a significant prognostic factor that was independent of well-established prognostic factors, including age, pathological stage, vascular invasion, lymphatic permeation, and serum carcinoembryonic antigen level. Conclusions: Positive EGFR mutation status is a favorable prognostic factor in patients with surgically resected lung adenocarcinomas; however, EGFR mutation subtype (exon 21 L858R mutation or exon 19 deletion) exhibits no prognostic impact.