EGFR and adenocarcinoma: There were significant differences between EGFR mutation-positive and EGFR mutation-negative groups with regard to sex (male vs female: P=0.00001), histology (adenocarcinoma vs non-adenocarcinoma: P=0.02) and smoking (>20 pack-years vs <20 pack-years: P=0.003) (Table 1).