Prognostic impact of cell type under the seventh TNM staging system in resected non-small cell lung cancer

Objectives: We retrospectively investigated whether histological cell type could affect patient prognosis for each stage according to the seventh edition of the TNM classification. Patients and methods: Clinical records of 1623 consecutive non-small cell lung cancer patients who underwent surgery between 1990 and 2007 were retrospectively reviewed. Over 92% of these patients had either adenocarcinoma (Ad; n = 1043, 64.3%) or squamous cell carcinoma (Sq; n = 452, 27.9%). Results: The overall 5-year survival rates for patients of all stages with Ad, Sq, large cell carcinoma (La), and adenosquamous cell carcinoma (As) were 67%, 56%, 58%, and 41%, respectively. Ad patients experienced better survival than Sq, As, or La patients (HR: 0.66, P < 0.0001; HR: 0.38, P = 0.011; HR: 0.69, P = 0.057, respectively). Stage IA Ad patients experienced better survival than stage IA Sq patients (5-year survival; Ad/Sq = 91%/78%, log-rank test, P = 0.001). Such a difference was also observed among seventh-edition TNM stage IB patients (5-year survival; Ad/Sq = 78%/64%, log-rank test, P = 0.048), but not for sixth-edition stage IB patients. Multivariate analysis demonstrated that histological cell type is a significant prognostic factor among stage I ≥ T1b Ad and Sq patients. Conclusions: Survival after complete resection of new stage I ≥ T1b Sq patients is significantly worse than that of Ad patients, which could be partially attributed to stage migration effect in stage IB disease between the sixth and seventh editions of the TNM staging system.