Preoperative risk score for prediction of long-term outcomes after hepatectomy for intrahepatic cholangiocarcinoma: Report of a collaborative, international-based, external validation study

Purpose: A preoperative risk score (PRS) to predict outcome of patients with intrahepatic cholangiocarcinoma treated by liver surgery could be clinically relevant.To assess accuracy for broadly adoption, external validation of predictive models on independent datasets is crucial. The objective of this study was to externally validate the score for prediction of long-term outcomes after liver surgery for intrahepatic cholangiocarcinoma proposed by Sasaki et al. and based on preoperative albumin, neutrophil-to-lymphocytes-ratio, CA19-9 and tumor size. Methods: Patients treated by liver surgery for intrahepatic cholangiocarcinoma at 11 international HPB centers from 2001 to 2018 were included in the external validation cohort. Harrell's c-index and Hosmer-Lemeshow analyses were used to test PRS discrimination and calibration. Kaplan–Meier curve for risk groups as described in the original study were displayed. Results: A total of 355 patients with 174 deaths during the follow-up period (median = 41.7 months, IQR 32.8–50.6) were included. The median PRS value was 14.7 (IQR 10.7–20.6), with normal distribution across the cohort. A Cox regression on PRS covariates found coefficients similar to those of the derivation cohort, except for tumor size. Measures of discrimination estimated by Harrell's c-index was 0.61(95%CI:0.56–0.67) and Hosmer-Lemeshow p = 0.175. The Kaplan-Meyer estimation showed reasonable discrimination across risk groups, with 5years survival rate ranging from 20.1% to 0%. Conclusion: In this external validation cohort, the PRS had mild discrimination and poor calibration performance, similarly to the original publication. Nevertheless, its ability to identify different classes of risk is clinically useful, for a better tailoring of a therapeutic strategy.