Inclusion Criteria:
1. Signing of written informed consent prior to participation;
2. Age ≥18 years, regardless of sex;
3. Histologically confirmed stage II/III biliary tract malignancies (including intrahepatic cholangiocarcinoma, extrahepatic/hilar cholangiocarcinoma, gallbladder cancer, distal bile duct cancer, or ampullary cancer);
4. Must have undergone radical resection (R0/R1), including liver/pancreatic resection or, less commonly, both;
5. ECOG performance status (PS) score: 0-1;
6. Expected survival \>6 months and ability to tolerate combined therapy;
7. Adequate organ function (without blood component or growth factor support within 14 days):
8. Hematology: Neutrophils ≥1,500/mm³, platelets ≥100,000/mm³, hemoglobin ≥9 g/dL;
9. Liver/kidney function: Serum creatinine (SCr) ≤1.5×ULN or creatinine clearance ≥50 mL/min (Cockcroft-Gault formula); total bilirubin (TBIL) ≤2×ULN; AST/ALT ≤3×ULN; urine protein \<2+ (if ≥2+, 24-hour urine protein ≤1 g); Biliary drainage: Adequate surgical drainage, no signs of infection;
10. Normal coagulation function, no active bleeding or thrombotic disease:INR ≤1.5×ULN, APTT ≤1.5×ULN, PT ≤1.5×ULN;
11. Contraception:
1. Non-surgically sterilized or reproductive-age patients must use medically approved contraception (e.g., IUD, oral contraceptives, condoms) during and for 3 months after treatment;
2. Reproductive-age females must have negative serum/urine pregnancy test (HCG) within 7 days before enrollment and must not be breastfeeding;
3. Reproductive-age males must agree to use contraception with partners during and for 3 months after treatment;
12. Voluntary participation, good compliance, and willingness to follow up for safety and survival assessments.
Exclusion Criteria:
1. Early-stage BTC patients;
2. Pancreatic cancer patients;
3. Patients who have undergone other postoperative radiotherapy/chemotherapy; preoperative chemoradiotherapy followed by radical resection, but postoperative pathology still indicates Stage II/III disease is allowed;
4. Incomplete surgical recovery or unresolved biliary obstruction;
5. Patients with radiologically confirmed distant metastasis;
6. Patients with a history of or concurrent other malignancies (except for cured basal cell carcinoma of the skin and in-situ carcinoma of other sites);
7. Known allergies to any component of the investigational drug;
8. Factors significantly affecting oral drug absorption, such as inability to swallow, chronic diarrhea, or intestinal obstruction;
9. Patients with any active autoimmune disease or a history of autoimmune disease (e.g., but not limited to: autoimmune hepatitis, interstitial pneumonia, uveitis, enteritis, hepatitis, hypophysitis, vasculitis, nephritis, hyperthyroidism, or hypothyroidism; patients with vitiligo or childhood asthma that has been completely resolved and requires no intervention in adulthood may be included; patients requiring bronchodilators for medical intervention due to asthma cannot be included);
10. Patients using immunosuppressants or systemic/absorbable local corticosteroids for immunosuppressive purposes (dose \>10 mg/day prednisone or equivalent) and continuing use within 2 weeks prior to enrollment;
11. Symptomatic ascites or pleural effusion requiring therapeutic paracentesis or drainage;
12. Poorly controlled cardiac symptoms or diseases, such as:
1. NYHA Class II or higher heart failure,
2. unstable angina,
3. myocardial infarction within 1 year,
4. clinically significant supraventricular or ventricular arrhythmias requiring treatment or intervention;
13. Coagulation abnormalities (PT \>16s, APTT \>43s, TT \>21s, Fbg \>2g/L), bleeding tendency, or receiving thrombolytic/anticoagulant therapy;
14. Active infection or unexplained fever \>38.5°C during screening or before the first dose;
15. History of abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within 4 weeks before the first dose;
16. History of pulmonary fibrosis, interstitial pneumonia, pneumoconiosis, radiation pneumonia, drug-related pneumonia, or severe lung dysfunction;
17. Congenital or acquired immunodeficiency, such as HIV infection, or active hepatitis (liver enzymes not meeting inclusion criteria; for hepatitis B: HBV DNA ≥103/ml; for hepatitis C: HCV RNA ≥103/ml); chronic HBV carriers with HBV DNA \<2000 IU/ml (\<104 copies/ml) may be included if receiving antiviral therapy during the trial;
18. Participation in other drug-related clinical trials within 1 month before enrollment or potential receipt of other systemic anti-cancer therapies during the study;
19. Live vaccination within 4 weeks before the first dose or planned during the study;
20. History of substance abuse, alcoholism, or drug addiction;
21. Inability or unwillingness to bear the cost of self-funded examinations and treatments;
22. Other factors deemed by the investigator to exclude the patient, such as severe diseases (including mental illness) requiring treatment, significant laboratory abnormalities, or family/social factors that may compromise patient safety or data/sample collection.
