Repeated Endobiliary Radiofrequency Ablation Plus Durvalumab, Gemcitabine, and Cisplatin for Unresectable Extrahepatic Cholangiocarcinoma

Inclusion Criteria: Histologically or cytologically confirmed extrahepatic cholangiocarcinoma (eCCA). Unresectable disease (unresectable due to tumor/patient factors, or patient refusal of surgery). Biliary obstruction requiring drainage, demonstrated by abnormal cholestatic liver tests, elevated bilirubin, radiologic evidence, or existing biliary drainage. Planned initiation of first-line systemic therapy with durvalumab + gemcitabine + cisplatin (GCD). Age ≥18 years. Able to provide written informed consent. Exclusion Criteria: Prior radiotherapy or systemic therapy for the current eCCA. Presence of a self-expanding metal stent that cannot be endoscopically removed. Surgically altered anatomy except for Billroth-I; prior biliary reconstruction. History of chronic cholangitis (e.g., primary sclerosing cholangitis, IgG4-related cholangitis). Expected survival \<3 months. Inability to insert an oral endoscope or reach the papilla. Contraindication to endobiliary RFA. Pregnancy or possible pregnancy. Any condition judged unsuitable by the investigator.