Prognostic Predictability of American Joint Committee on Cancer 8th Staging System for Perihilar Cholangiocarcinoma: Limited Improvement Compared with the 7th Staging System

PURPOSE: This study was conducted to evaluate the prognostic values of the 7th and 8th American Joint Committee on Cancer (AJCC) staging systems for patients with resected perihilar cholangiocarcinoma (PHCC). MATERIALS AND METHODS: A total of 348 patients who underwent major hepatectomy for PHCC between 2008 and 2015 were identified from a single center. Overall survival (OS) was estimated using the Kaplan-Meier method and compared across stage groups with the log-rank test. The concordance index was used to evaluate the prognostic predictability of the 8th AJCC staging system compared with that of the 7th. RESULTS: In the 8th edition, the stratification of each group of T classification improved compared to that in the 7th, as the survival rate of T4 decreased (T2, 31.2%; T3, 13.9%; T4, 15.1%; T1-T2, p=0.260; T2-T3, p=0.001; T3-T4, p=0.996). Both editions showed significant survival differences between each N category, except between N1 and N2 (p=0.063) in 7th edition. Differences of point estimates between the 8th and 7th T and N classification and overall stages were +0.028, +0.006, and +0.039, respectively (T, p=0.005; N, p=0.115; overall stage, p=0.005). In multivariable analysis, posthepatectomy liver failure, T category, N category, distant metastasis, histologic differentiation, intraoperative transfusion, and resection margin status were associated with OS. CONCLUSION: The prognostic predictability of 8th AJCC staging for PHCC improved slightly, with statistical significance, compared to the 7th edition, but its overall performance is still unsatisfactory.