Difference of Postoperative Survival Due to the Type of EGFR Gene Mutation in Surgically Resected Lung Adenocarcinomas

Epidermal growth factor receptor (EGFR) gene mutation is a robust prognostic factor in patients with advanced lung adenocarcinomas. Recently, on the other hand, there are some reports proposing the difference of survival due to the type of EGFR mutation. In this study, we analyzed the difference of postoperative survivals between two most common mutations, that is, exon 19 deletions (DEL) and exon21 L858R (PM), using multi-institutional data of patients with surgically resected lung adenocarcinomas. We retrospectively collected 1,063 consecutive patients who underwent surgical resections for lung adenocarcinoma between 2005 and 2012 in five institutions, and who were examined their EGFR mutation status. The patients with minor EGFR mutations were excluded. We compared their clinicopathological characteristics among DEL, PM, and wild type (WT) group. We also analyzed postoperative recurrence-free survival (RFS) and overall survival (OS) according to the type of EGFR mutation. The number of patients with DEL, PM, and WT was 218 (20.5%), 301 (28.3%), and 544 (51.2%) respectively, and their median follow-up period was 47.6 months. The patients of PM were older and earlier pathological staged than those with DEL, whereas no significant difference was observed among other clinicopathological factors. Five-year RFS and OS of DEL, PM, and WT were 67.3/85.9%, 76.4/88.6%, 59.2/71.5%, respectively, and both survivals of each mutant were significantly better than those of WT. Regarding the difference between DEL and PM, RFS curve of DEL was significantly worse than that of PM (p = 0.027), but OS curves of both mutant weren’t significantly different. (p = 0.16). In multivariate analysis, the type of EGFR mutation (DEL vs PM) was not an independent factor both in RFS and OS. Exon 21 L858R might be a more favorable recurrence-risk factor than exon 19 deletions in patients with surgically resected lung adenocarcinomas.