Validation of the American Joint Committee on Cancer eighth edition staging system in patients undergoing hepatectomy for hepatocellular carcinoma: a US population-based study.

BACKGROUND: The American Joint Committee on Cancer (AJCC) eighth edition staging system for hepatocellular carcinoma (HCC) has incorporated several significant changes. This study aims to evaluate the newly proposed staging system and assess its strengths and weaknesses.

MATERIALS AND METHODS: Using the Surveillance, Epidemiology, and End Results database, we identified patients with pathologically confirmed stage I-III HCC diagnosed between 2004 and 2014.

RESULTS: After all exclusion criteria were applied, AJCC seventh and eighth edition staging was possible in 4931 patients. According to the AJCC eighth edition staging system, stages IB and II did not differ significantly in terms of overall survival (OS) and cause-specific survival (CSS) (P = 0.928 and 0.872, respectively). On the basis of the above results, we reclassified T1a, T1b, and T2 into several subgroups. According to the modified AJCC eighth edition staging system, OS and CSS among the five groups of patients differed significantly. For OS predication, the Akaike information criterion values for the AJCC seventh, eighth, and modified eighth edition staging systems were 29,288.24, 29,282.85, and 27,182.21, respectively, and the c-indices for the AJCC seventh, eighth, and modified eighth edition staging systems were 0.5716, 0.5805, and 0.6082, respectively. Regarding CSS, the Akaike information criterion values for the AJCC seventh, eighth, and modified eighth edition staging systems were 21,701.11, 21,682.12, and 20,313.26, respectively, and the c-indices for the AJCC seventh, eighth, and modified eighth edition staging systems were 0.5983, 0.6117, and 0.6436, respectively.

CONCLUSIONS: This is the first large-scale validation of the AJCC eighth edition staging system for patients undergoing hepatectomy. Our study revealed that there was a lack of discrepancy in the outcomes for stage IB and II tumors for AJCC eighth edition staging system of HCC. Our modified AJCC eighth edition staging system allows for finer stratification of patients undergoing hepatectomy according to more detailed tumor size and vascular invasion classifications.