Conditional survival after curative resection for extrahepatic cholangiocarcinoma: a comprehensive analysis of overall, recurrence-free, and relative survival

Background: Conditional survival offers dynamic, time-adjusted prognostic information but remains understudied in extrahepatic cholangiocarcinoma (EHCC). This study evaluated conditional overall survival (COS), conditional recurrence-free survival (CRFS), and conditional relative survival (CRS) after curative-intent resection for EHCC. Methods: We conducted a retrospective cohort study of 1266 patients who underwent curative-intent resection for EHCC (hilar, n = 424; common bile duct cancer [CBDC], n = 842) at a single institution between 2005 and 2019. Conditional 5-year COS, CRFS, and CRS were calculated annually using Kaplan–Meier methods and compared across demographic, clinical, and tumor-related subgroups. Results: At baseline, 5-year COS, CRFS, and CRS were 41.3 %, 29.3 %, and 47.9 %, respectively, improving to 51.9 %, 50.0 %, and 59.3 % at five years post-surgery. Stage III patients demonstrated the largest gains in COS (24.7 %–51.0 %) and CRFS (14.6 %–53.3 %). Younger patients and females consistently had superior outcomes, whereas obese patients and those receiving adjuvant therapy showed less favorable long-term trends. Conditional survival patterns were similar between hilar and CBDC. Conclusion: Conditional survival in EHCC improves substantially with time survived, particularly among advanced-stage, younger, and female patients. However, nearly 40 % remain at risk of recurrence even after 5 recurrence-free years. Conditional estimates provide dynamic insights to guide counseling and surveillance.