External validation study of the 8th edition of the American Joint Committee on Cancer staging system for perihilar cholangiocarcinoma: a single-center experience in China and proposal for simplification.

Background Several changes have been made to the primary tumor (T) and lymph node (N) categories in the new 8th edition of the American Joint Committee on Cancer (AJCC) staging system for perihilar cholangiocarcinoma (pCCA). This study was conducted to validate the 8th edition of the AJCC staging system for pCCA in China. Methods A total of 335 patients who underwent curative-intent resection for pCCA between January 2010 and December 2018 were retrospectively enrolled. The overall survival (OS) of groups of patients was calculated using the Kaplan-Meier method. The log-rank test was used to compare OS between groups. The concordance index (C-index), Akaike information criteria (AIC), and time-dependent area under receiver operating characteristic (ROC) curve (AUC) were computed to evaluate the discriminatory power of the 8th and 7th editions of the AJCC staging system. Results The T category changed in 25 (7.5%) patients, the N category changed in 39 (11.6%) patients, and the tumor-node-metastasis (TNM) stage changed in 157 (46.9%) patients when the 8th and 7th editions were compared. No statistically significant difference in survival was observed between T2aN0M0 and T2bN0M0. The C-index of the 8th edition was 0.609 [95% confidence interval (CI): 0.568-0.650], which was slightly higher than that of the 7th edition (C-index, 0.599, 95% CI: 0.558-0.640). The time-dependent AUC value also corroborated that the 8th edition had a better performance than the 7th edition. Conclusions The 8th edition of the AJCC staging system for pCCA showed a better ability than the 7th edition to discriminate patient survival. However, further simplification of the 8th edition is still needed.