Proposed Modification of the 8th Edition of the AJCC Staging System for Gastric Cancer

Background: The American Joint Committee on Cancer (AJCC) staging system has been the standardized staging system for malignancies since the first edition in 1987. The 8th edition of gastric cancer was released in 2016, and is expected to be used in clinical practice in 2018. The aim of this study was to improve this new gastric cancer staging system. Methods: We conducted median overall survival analyses in a cohort of 8359 gastric cancer patients from the Surveillance, Epidemiology, and End Results (SEER) database (2004–2014) via Kaplan–Meier curves and log-rank tests, and proposed a modified staging system based on median OS. The concordance index (C-index) was conducted to evaluate the predictive accuracy. Results: Using the 8th AJCC staging system, the median OS of patients at the same stage varied widely between the different substages, especially in stage III. Despite the definitions of T, N, and M, substages in the modified staging system were regrouped based on median OS. The C-index of stage III patients with the modified staging system [0.579, 95% confidence interval (CI) 0.564–0.593] was higher than the 8th AJCC staging system (0.567, 95% CI 0.552–0.581). Moreover, we divided these patients into two groups according to their examined lymph node counts (≥15 or 1–14), and studied the effectiveness of the modified staging system in the two groups. Conclusions: The modified 8th AJCC staging system for gastric cancer proposed in this study generates better prognostic stratifications and may be evaluated for further update. Abbreviations:AJCCAmerican Joint Committee on CancerOSOverall SurvivalSEERSurveillance, Epidemiology, and End Results