Never-smoking nonsmall cell lung cancer as a separate entity: Clinicopathologic features and survival

BACKGROUND. To propose 'never-smoking nonsmall cell lung cancer (NSCLC)' as a separate entity, the clinicopathologic differences of operable NSCLC between never-smoking patients and patients with a history of smoking were investigated. METHODS. The medical records of 1405 patients with primary NSCLC who underwent a complete resection at the study institution from 1974 through 2004 were reviewed for clinicopathologic variables and postoperative survival. RESULTS. The proportion of never-smoking patients with NSCLC has been significantly increasing over 30 years, from 15.9% in the 1970s to 32.8% in the 2000s. A significantly greater proportion of female patients or adenocarcinoma patients was found in the 'never-smoking NSCLC' group in comparison to the 'smoking NSCLC' group (85.8% vs 11.2% and 87.8% vs 49.1%, respectively). The proportion of pathologic stage IA disease for the 'never-smoking NSCLC' group was significantly higher than that for the 'smoking NSCLC' group (40.1% vs 25.4%; P < .0001). With regard to both overall and cancer-specific survival, the 'nevers-moking NSCLC' patient group was significantly superior to the 'smoking NSCLC' group. In addition to smoking status, the factors found to be significantly associated with the postoperative survival rate were sex, histologic type, T classification, and N classification by univariate analyses. A multivariate analysis revealed never-smoking status to be an independent prognostic factor in addition to pathologic T and N classification. CONCLUSIONS. The differences in the clinicopathologic factors and survivals between the 'never-smoking NSCLC' patient group and the 'smoking NSCLC' group suggest that NSCLC in never-smokers should be considered a separate disease entity.