Comparison of 6th, 7th, and 8th editions of the TNM staging in non-small cell lung cancer patients: Validation of the 8th edition of TNM staging

BACKGROUND: In this study, we aimed to evaluate the effects of the transition from the 6(th) edition of the Tumor, Node, Metastasis (TNM) staging system to the 7(th) edition, and from the 7(th) edition to the 8(th) edition by comparing the stage migrations. We also aimed to externally validate the 8(th) edition of the TNM staging system. METHODS: Between September 2005 and June 2015, a total of 1,077 patients (986 males, 91 females; mean age: 59.6±8.3 years; range, 35 to 84 years) with non-small cell lung cancer who underwent lung resection were retrospectively analyzed. We re-staged patients according to 6(th), 7(th), and 8(th) TNM staging and compared the stage migrations of cases among the three staging systems. RESULTS: Stage migration in the transition to the 7(th) edition of the TNM staging system was observed in 368 (34.1%) patients whereas it was observed in 541 (50.2%) patients in the transition to the 8(th) edition (p<0.001). The rate of upstaging in transition to the 7(th) edition staging system was 50.2% (n=185), whereas it was 98.1% (n=531) for the transition to the 8(th) edition (p<0.001). The survival rates of Stages 1B, 2B and 3A increased with transition to the 7(th) edition and the survival rates of Stages 1B, 2A, 2B, 3A, and 3B increased with the transition to the 8(th) edition. The best stratification in the survival curves in the 6th edition was between 1B-1A and 3B-3A. In the 7(th) edition, it occurred between 1B-1A, 3A-2B and 3B-3A and, in the 8(th) edition, between 1B-1A and 3B-3A. CONCLUSION: Stratification according to the 7(th) edition showed better prognostic validity compared to the 6(th) edition; and that of the 8(th) edition was better compared to the 7(th) edition.