Evaluation of the 8th edition American Joint Commission on Cancer (AJCC) staging system for patients with intrahepatic cholangiocarcinoma: A surveillance, epidemiology, and end results (SEER) analysis

Background: The objective of this study was to assess the prognostic performance of American Joint Committee on Cancer (AJCC) 8th edition in patients with intrahepatic cholangiocarcinoma (ICC) using a cancer registry. Methods: The Surveillance, Epidemiology, and End Results (SEER) cancer registry was queried to identify 1008 patients who underwent surgical resection of ICC during 1998-2013. Kaplan-Meier method and Cox proportional hazards regression models were used to analyze long-term survival. The relative discriminative abilities were assessed using the Harrell's concordance index. Results: Median patient age was 62 years and 47.6% of the patients were male. Most tumors were T1 or T2 (n = 413, 41.0% and n = 329, 32.6%, respectively) and 22.1% of patients had lymph node (LN) metastasis. Median tumor size was 5.5 cm. With a median follow-up of 18 months, median survival was 27 months and 5-year OS was 30.6%. The OS c-index for the AJCC 8th staging system was 0.669, which was comparable with the c-index for the 7th edition AJCC staging system (c-index: 0.667); the AJCC 8th-edition did provide more discrete stratification of patients. Conclusions: The new AJCC 8th-edition staging system for ICC was largely comparable to the 7th-edition version and did not provide a marked improvement in overall prognostic discrimination.