Histological subtype and smoking status, but not gender, are associated with epidermal growth factor receptor mutations in non-small-cell lung cancer

Mutations in epidermal growth factor receptor (EGFR) commonly occur in non-small-cell lung cancer (NSCLC) patients characterized by female gender, never-smoker status and adenocarcinoma histology. The aim of this study was to determine whether gender is a confounding factor for EGFR mutations in NSCLC. To elucidate the confounding effect, Pearson's chi(2) test and logistic regression models were used to correlate these characteristics with EGFR mutations in 426 NSCLC patients treated at our institutes. Of those 426 NSCLC patients, 47% were females, 57% were non-smokers and 84% had adenocarcinomas. The multivariate logistic regression analysis demonstrated that never-smoker status [odds ratio (OR)=3.49, 95% confidence interval (CI): 1.99-6.13; P<0.001)] and adenocarcinoma (OR=9.43, 95% CI 3.62-24.56; P<0.001) were associated with EGFR mutations; however, gender was not (OR=1.25, 95% CI: 0.73-2.15; P=0.416). Furthermore, gender was not associated with EGFR mutation subtypes (OR=1.19, 95% CI: 0.56-2.50; P=0.650). The frequency of EGFR mutations among females and males was not different in non-smokers (64.8 vs. 55.8%, P=0.204) or ever-smokers (27.8 vs. 24.2%, P=0.775). Therefore, if the assessment for EGFR mutation status was limited to non-smoking females with adenocarcinoma, up to 40% of the patients harboring EGFR mutations would be precluded from the benefit of EGFR inhibitor therapy. Our results indicated that gender is a confounding factor for EGFR mutations in NSCLC and suggested that gender may not be associated with tumorigenesis in NSCLC-harboring EGFR mutations.