Validation of the 8th AJCC TNM staging system for gastric cancer: Survival analysis with high volume Asian centers and SEER database by comparing with 7th TNM staging system.

Abstract

18 Background: Recently, the 8th AJCC TNM staging system for estimating prognosis for patients with gastric cancer was revised with new subgroups. There are little number of studies have shown its validation with other datasets. We aimed to validate the new TNM staging system by using various datasets with large number of gastrectomies. Methods: We retrospectively reviewed data of 17160, 11324 and 1500 patients treated for gastric cancer in Yonsei University Severance Hospital (SH), The Surveillance, Epidemiology, and End Results (SEER) and Gangnam Severance Hospital (GSH), respectively. Survival curves were plotted and the performance of tumor staging defined by the 7th and 8th TNM staging was compared based on the log-rank test, Concordance index (C-index) and Akaike information criterion (AIC). Results: The performance of predicting survival using the 8th TNM staging system is superior to that of the previous version in SH by evaluating log-rank, C-statistics, and AIC (8444.5 vs. 9263.8, 0.796 vs. 0.798, 104152 vs. 103909), respectively. It is also superior in a data with SEER and GSH (log-rank, C-statistics, and AIC; 3342 vs. 3527, 0.7064 vs. 0.709, 100931 vs. 100820 in SEER, 973 vs. 1031, 0.8021 vs. 0.8038, 7173 vs. 7154 in GSH), respectively. In subgroup analysis of each subclassification, IA, IB, IIA, IIB, IIIA, IIIB, IIIC, and IV in SH, the 8th TNM staging system shows similar or more homogenous survival (0.0324 vs. < 0.001 in Stage IIB, 0.020 vs. < 0.0001 in Stage IIIB, 0.0004 vs. < 0.0001 in Stage IIIC, respectively) in each subclassification than that of the 7th TNM staging system by measuring log-rank p values. Conclusions: The 8th TNM staging system provides more accurate prediction of prognosis of gastric cancer patients than the previous one. In addition, each subgroup in the same stage is relatively homogenous with respect to survival than the previous staging system. It is also applicable to Eastern and Western patients with various backgrounds.