Improved prognostic stratification of the revised ninth edition American Joint Committee on Cancer staging system for colorectal cancer

BACKGROUND The 9th edition American Joint Committee on Cancer (AJCC) staging system has been proposed by the AJCC Cancer Expert Panel (AJCCCCEP). The prognostic discriminatory validity of the new staging system in actual patient cohorts has not been fully validated. AIM To investigate and validate the proposed changes to the pathologic staging for colon cancer (CC) and rectal cancer (RC) by the AJCCCCEP. METHODS The study included 1251 eligible patients with stage I-III CC and 1162 patients with RC between July 2015 and July 2021. Clinicopathological features of the patients were obtained. Patients were staged according to 8th edition AJCC staging system and 9th edition AJCC staging system, respectively. Patients’ outcomes were investigated with respect to overall survival (OS) and disease-free survival (DFS) according to the 8th edition and 9th edition, respectively. The Kaplan-Meier curve and log-rank test were conducted to compare outcomes of patients with different stages. Hazard ratio was calculated using the Cox proportional hazard model. RESULTS One thousand, two hundred and fifty-one patients with CC and 1162 patients with RC were analyzed, with a median follow-up of 5.45 and 5.30 years for DFS and OS in the CC cohort and 5.36 and 5.35 years in the RC cohort. All patients were re-classified according to the updated staging system proposed by AJCCCCEP. The survival analysis revealed a hierarchical separation across all sub-levels in the CC cohort and the RC cohort in terms of DFS and OS. CONCLUSION This study indicates that the 9th edition AJCC staging system has better prognostic validity than the 8th edition AJCC staging system for patients with CC and RC.