EGFR and neoplasm: Stratification analyses were conducted based on age (≥ 65 vs. < 65 years), gender (male and female), smoking behavior (smoking and nonsmoking), tumor stage (stage 3–4: advanced-stage and stage 1–2: early-stage), KRAS mutation status (mutation and wild-type) and EGFR mutation status (mutation and wild-type) in the entire set (Figs. 3, 4).