Real-World Efficacy and Safety of Gemcitabine, Cisplatin, Plus Immune Checkpoint Inhibitors in Biliary Tract Cancer: A Retrospective Analysis

Background: Based on the demonstrated survival benefits of gemcitabine plus cisplatin (GemCis) therapy in the TOPAZ-1 and KEYNOTE-966 trials, GemCis plus immune checkpoint inhibitor (ICI) therapy has become a standard first-line treatment for unresectable biliary tract cancer. However, its safety and efficacy in elderly patients and those requiring biliary drainage remain insufficiently evaluated in real-world practice. We aimed to evaluate the efficacy and safety of GemCis plus ICI therapy, with a focus on elderly patients and those requiring biliary drainage. Methods: We retrospectively analyzed the clinical characteristics of patients with unresectable biliary tract cancer treated with GemCis plus ICI at our institution between April 2022 and September 2025. Progression-free survival (PFS) was analyzed using the Kaplan–Meier method, and prognostic factors were examined using Cox proportional hazards models. PFS and immune-related adverse events (irAEs) were compared between durvalumab and pembrolizumab. Results: Of the 51 patients diagnosed with unresectable biliary tract cancer during the observation period, 26 (51.0%) received GemCis plus ICI therapy. The median age was 73 years (range, 46–83 years), and 15 (57.7%) patients were male. Distant metastases were present in 22 patients (84.6%), and biliary drainage was performed in 15 (57.7%). The primary tumor sites were intrahepatic cholangiocarcinoma (n = 8), perihilar cholangiocarcinoma (n = 6), gallbladder cancer (n = 11), and cancer of unknown primary origin (n = 1). The ICIs used were durvalumab in 18 patients and pembrolizumab in eight patients. The median follow-up period was 214 days (range, 30–1114). The response rate was 28.6%, the disease control rate was 90.5%, and the transition rate to ICI maintenance therapy was 29.2%. IrAEs occurred in six patients (23.1%), with a significantly higher frequency in the pembrolizumab group than in the durvalumab group (50.0% vs. 11.1%). The median PFS was 8.2 months in the durvalumab group and 8.9 months in the pembrolizumab group, with no significant difference (p = 0.88). Multivariate analysis incorporating age, performance status, metastatic burden, and liver function confirmed that age ≥ 75 years remained the only independent predictor of shorter PFS (HR 5.62; 95% CI, 1.35–23.4; p = 0.02), whereas ICI regimen and biliary drainage were not significant prognostic factors. Conclusions: In clinical practice, GemCis plus ICI therapy showed no statistically significant difference in efficacy between ICI regimens in this small cohort, although this comparison was not statistically powered. Given the exploratory nature of these findings, the lower incidence of immune-related adverse events (irAEs) observed in the durvalumab group should be interpreted with caution. Age ≥ 75 years was associated with shorter PFS. Careful patient selection is warranted when considering GemCis plus ICI therapy in elderly patients with biliary tract cancer.