Clinical and pathological characteristics of EGFR mutation in operable early-stage lung adenocarcinoma

Abstract Objectives Over the past decade, the biological and clinical characteristics of lung cancer with epidermal growth factor receptor ( EGFR ) mutation have been well studied. However, most studies have focused on advanced inoperable cancer, and not on resected early-stage lung adenocarcinoma. We aimed to elucidate the differences in the clinicopathological characteristics and postoperative prognosis according to the EGFR mutation status in early-stage lung adenocarcinoma. Materials and methods We retrospectively collected clinical and pathological data from 369 patients with pathological stage I or II lung adenocarcinoma who underwent complete resection. Clinicopathological characteristics and postoperative prognosis were compared depending on the EGFR mutation status, using the Chi-squared test and the log-rank test, respectively. Results and conclusion Of the 369 patients, 160 (43.3%) had EGFR mutation, of which 64 (40.0%) were exon 19 deletion (Del-19) and 90 (56.3%) were exon 21 point mutation L858R. Although there was no difference in overall survival (OS) between patients with and without EGFR mutation ( p  = 0.086), tumors with EGFR mutation were associated with a lower consolidation to tumor ratio (CTR) ( p  0.001) and a higher incidence of a lepidic growth pattern by pathological evaluation ( p  0.001) compared to those without EGFR mutation. Among tumors with EGFR mutation, there was no difference in OS ( p  = 0.140) between Del-19 and L858R. Tumors with L858R were associated with a lower CTR ( p  = 0.046), and tended to have a higher incidence of a lepidic growth pattern by pathological evaluation ( p  = 0.073) compared to those with Del-19. In conclusion, although EGFR mutation status was not a prognostic indicator after surgery in early-stage lung adenocarcinoma, L858R and Del-19 had different radiological and pathological features.