In the multivariate analysis, adenocarcinoma (HR 0.356, 95% CI 0.188–0.674), clinically undetected lymph node metastasis (HR 0.427, 95% CI 0.263–0.692), and EGFR mutation (HR 0.263, 95% CI 0.139–0.500) were favorable independent prognostic factors (Table 2). Here, EGFR is linked to adenocarcinoma.