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

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.