Combination of Gemcitabine, Oxaliplatin, Sintilimab and Bevacizumab in Unresectable Biliary Tract Cancer

Inclusion Criteria: 1. Age ≥18 and ≤80 years; 2. ECOG 0\~1; 3. Histologically or cytologically confirmed carcinoma of the bile duct or gallbladder; 4. Imaging assessment of disease stage III/IVA/any TN1M0\*; 5. The main organs have good functions and the examination indexes meet the following requirements: 6. Blood routine test: Hemoglobin ≥90 g/L (no blood transfusion within 14 days); Neutrophils count ≥1.5×10\^9/L; Platelet count ≥80×10\^9/L; 7. Biochemical tests: Total bilirubin ≤2×ULN (upper limit of normal value); Blood alanine aminotransferase (ALT) or blood aspartate aminotransferase (AST) ≤ 2.5×ULN; Endogenous creatinine clearance rate ≥ 50 mL /min (Cockcroft-Gault formula); 8. Voluntarily signed the informed consent; 9. Good compliance and family members are willing to cooperate with follow-up. Exclusion Criteria: 1. Other uncured malignancies; 2. Pregnant or lactating women, if the subject becomes pregnant during the study period, should withdraw from the clinical trial; 3. Previous anti-tumor therapy for the disease in this study; 4. Participated in other drug clinical trials within one month; 5. Patients with known history of other systemic serious diseases before screening; 6. Long-term unhealed wounds or incomplete healed fractures; 7. Have a history of organ transplantation; 8. Abnormal blood coagulation, with bleeding tendency (14 days before randomization must meet: INR within the normal range without the use of anticoagulants); Patients treated with anticoagulants or vitamin K antagonists such as warfarin, heparin or their analogs; The use of low-dose warfarin (1 mg orally, once daily) or low-dose aspirin (not more than 100 mg daily) for prophylactic purposes is permitted, provided that INR is less than 1.5; 9. The incidence of arterial/venous thrombosis events in the previous year, such as cerebrovascular accident (including temporary ischemic attack), deep venous thrombosis and pulmonary embolism, was screened; 10. People with a history of psychotropic substance abuse and unable to get rid of it or with mental disorders; Have a history of immunodeficiency, or other acquired or congenital immunodeficiency diseases, or have a history of organ transplantation; 12\. Concomitant diseases that, in the Investigator's judgment, seriously endanger patient safety or affect patient completion of the study.