Primary tumor removal with targeted lymph node removal plus radiation for biliary tract cancer with lymph node spread

Inclusion Criteria:

1. Patients with suspected biliary tract carcinoma who are eligible for surgical exploration, with postoperative pathological confirmation of biliary tract adenocarcinoma;
2. Age 18-80 years;
3. Preoperative assessment indicating that the primary tumor is potentially amenable to R0/R1 resection;
4. Preoperative evidence of lymph node metastases with at least one of the following features indicating that complete surgical resection or lymph node dissection may not be feasible:

   * Local invasion of regional lymph nodes, such that complete surgical resection may not be feasible;
   * Retroperitoneal lymph node metastases extending beyond the feasible surgical dissection field;
5. Whole-body PET/CT demonstrating metastatic lymph node involvement confined to a contiguous extended lymphatic field that can be encompassed within a single radiotherapy plan, with the involved lymph nodes extending from the lower paraesophageal lymph node region superiorly to the lymph nodes at the level of the abdominal aortic bifurcation inferiorly;
6. No distant organ metastases, non-regional lymph node metastases, or intrahepatic metastatic lesions are allowed. Isolated right internal mammary lymph node or left supraclavicular lymph node involvement is permitted; however, these lesions will not be included in the initial radiotherapy field and may receive subsequent definitive local radiotherapy based on multidisciplinary evaluation and treatment response;
7. Prior systemic therapy, including chemotherapy, targeted therapy, or immunotherapy, is permitted. Prior local treatment, including interventional therapy or radiofrequency ablation, is not permitted;
8. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 and a life expectancy of \>3 months;
9. Child-Pugh class A5 or A6;
10. Liver function meeting the following criteria:

    * ALT ≤2.5 × the upper limit of normal (ULN), with AST ≤6 × ULN when ALT ≤1.5 × ULN and AST ≤2.5 × ULN when ALT \>1.5 × ULN but ≤2.5 × ULN, after excluding AST elevation due to myocardial infarction;
    * Total bilirubin (TBIL) \<60 μmol/L.
11. No clinically significant abnormalities on electrocardiography, no significant cardiac insufficiency, and no contraindication to treatment with PD-1/PD-L1 inhibitors;
12. Adequate renal function, defined as serum creatinine (CRE) and blood urea nitrogen (BUN) ≤2.5 × ULN;
13. Adequate hematologic function, defined as hemoglobin (Hb) ≥80 g/L, absolute neutrophil count (ANC) ≥0.5 × 10⁹/L, and platelet count (PLT) ≥80 × 10⁹/L;
14. Patients voluntarily participate in this clinical trial and sign an informed consent form.

Exclusion Criteria:

1. Current participation in another interventional clinical trial involving an investigational drug or treatment;
2. Previous abdominal radiotherapy or liver transplantation;
3. Previous local treatment for the current malignancy, including interventional therapy or radiofrequency ablation;
4. Known or suspected drug dependence, substance abuse, or alcohol abuse;
5. Pregnancy or breastfeeding;
6. Severe psychiatric or neurological disorders that may interfere with the ability to provide informed consent or with the reporting or assessment of adverse events;
7. Concurrent second primary malignancy or a history of another malignancy diagnosed within 3 years before enrollment, except for superficial skin cancers, localized low-grade malignancies, or carcinoma in situ that have been adequately treated and are not considered potentially life-threatening due to disease progression;
8. Severe unhealed wounds, ulcers, or fractures;
9. Biliary fistula, gastrointestinal perforation, or intra-abdominal abscess within 4 weeks before enrollment;
10. Unstable angina, myocardial infarction, coronary artery bypass grafting, congestive heart failure, or cerebrovascular events, including transient ischemic attack or pulmonary embolism, within 3 months before enrollment;
11. Persistent arrhythmia of CTCAE grade ≥2, atrial fibrillation of any grade, or prolonged QTc interval (QTc \>450 ms in males or \>470 ms in females);
12. Known HIV infection.