Superiority of the 8th edition of the TNM staging system for predicting overall survival in gastric cancer: Comparative analysis of the 7th and 8th editions in a monoinstitutional cohort

The present study was performed to evaluate the predictive capacity of the 8th edition vs. the 7th edition of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) staging system for overall survival (OS) of patients with gastric cancer. Data of eligible patients with gastric cancer in our institution between June 2004 and June 2014 were retrospectively reviewed. A total of 1,506 patients were followed up to July 2016, among whom 1,484 patients with complete stage information were included in the TNM staging analysis. A total of 339 (22.8%) patients presented stage migration, including 325 (21.9%) migrating to a lower tier and 14 (0.9%) to a higher tier. All patients with stage migration to a lower tier were in stage III, including 177 (54.5%) patients migrating from stage IIIB to IIIA, and 148 (45.5%) from stage IIIC to IIIB. Patients migrating from IIIB to IIIA yielded a median OS time and 5-year OS rate closer to those remaining in stage IIIA. Similarly, patients migrating from IIIC to IIIB yielded a median OS time and 5-year OS rate closer to those remaining in stage IIIB. The 7th edition of the staging system exhibited prognostic discrepancy in discriminating stage IIIA from IIIB on survival curves, which was improved in the 8th edition. The 8th edition had a better predictive capability of survival, as evidenced by a smaller value of -2log likelihood in the Cox proportional regression model (7th edition 4738.859 vs. 8th edition 4736.683). Therefore, the present study demonstrated that the 8th edition of the AJCC TNM staging system is superior to the 7th edition in predicting the OS of patients with gastric cancer.