Efficacy and Safety of Postoperative Concurrent Chemoradiotherapy for Extrahepatic Cholangiocarcinoma and Gallbladder Carcinoma: A Multicenter Prospective Phase II Study

Inclusion Criteria: * Aged 18-80 years * Underwent curative resection for newly diagnosed disease, with postoperative pathology confirming extrahepatic cholangiocarcinoma or gallbladder adenocarcinoma * Postoperative pathology with ≥1 high-risk factor for recurrence 1. Narrow resection margin (\<1 cm), including R1 resection 2. Positive circumferential resection margin 3. T stage ≥ T3-4 4. Positive regional lymph nodes * Postoperative liver function: Child-Pugh grade A5-B7 * No recurrence or metastasis before postoperative radiotherapy * ECOG performance status 0-2 * Expected survival \>3 months * Routine blood tests: Neutrophils ≥1.0×10⁹/L, hemoglobin ≥80 g/L, platelets ≥100×10⁹/L * Liver function: Total bilirubin \<1.5×upper limit of normal (ULN), plus one of the following: 1. ALT and AST ≤2.5×ULN 2. ALT ≤1.5×ULN and AST ≤6×ULN (excluding AST elevation due to myocardial infarction) * Renal function: Creatinine and blood urea nitrogen ≤2.5×ULN * Voluntary participation and signed informed consent Exclusion Criteria: * History of other malignant tumors (except papillary thyroid carcinoma, basal cell carcinoma of the skin, and cervical carcinoma in situ) * Severe comorbidities (e.g., myocardial infarction, arrhythmia, psychiatric disorders) * Prior abdominal radiotherapy * Post-organ transplantation * Symptomatic moderate-severe ascites within 4 months postoperatively * ≥4 months since surgery