Postoperative survival of extrahepatic and intrahepatic cholangiocarcinoma after surgery: a population-based cohort

Objectives The study was designed to clarify the difference between extrahepatic cholangiocarcinoma (ECC) and intrahepatic cholangiocarcinoma (ICC) in postoperative cancer-specific death. Design Patients diagnosed with ECC and ICC after surgery, who are identified from the Surveillance, Epidemiology and End Results programme, are eligible for this retrospective cohort study. Setting Survival between groups was compared using the traditional Kaplan-Meier method and the cumulative incidence function (CIF) method. Propensity score-matched (PSM) analysis was conducted to balance the differences in vital variables between groups. The HR and 95% CI for ECC relative to ICC were used to quantify the risk of death. Subgroup analysis was further used to evaluate the stability of the differences between groups. Results The study included 876 patients with ECC and 1194 patients with ICC. Before PSM, with the Kaplan-Meier method, postoperative overall survival and cancer-specific death for ECC were worse than those for ICC. However, with the CIF method, no difference in postoperative cancer-specific death was found. After PSM, all differences in the considered traits were balanced, and 173 pairs of patients were retained. Survival analysis found that there was no difference in postoperative all-cause death (Kaplan-Meier method, p=0.186) or cancer-specific death (Kaplan-Meier and CIF methods, p=0.500 and p=0.913, respectively), which was consistent with subgroup analysis. Conclusions ECC and ICC showed no difference in postoperative cancer-specific death, both in the natural state and in multiple variable-matched conditions.