COmbination of Radiotherapy With Anti-PD-1 Antibody for unREseCtable Biliary Tract Cancer

Inclusion Criteria: 1. Aged between 18 and 75 years old; 2. Histopathologically confirmed unresectable primary or initial postoperative recurrent BTC without distant metastasis; 3. No previous radiotherapy or systemic therapy; 4. Adequate volume of the uninvolved liver (larger than 700 mL); 5. At least one measurable lesion based on Response Evaluation Criteria in Solid Tumors 1.1 criteria; 6. Eastern Cooperative Oncology Group performance status score of 0 or 1; 7. Adequate hematologic (absolute neutrophil count ≥ 1.5x109/L, hemoglobin concentration ≥ 90g/L, platelet count ≥ 100 x109/L), hepatic (albumin ≥ 28 g/L, total bilirubin \< 1.5 times the upper limit of normal (ULN), alanine aminotransferase and aspartate aminotransferase \< 5×ULN) and renal function (serum creatine \< 1.5×ULN, creatinine clearance rate ≥ 45ml/min); 8. Life expectancy of at least 12 weeks. Exclusion Criteria: 1. Have acute or chronic active hepatitis B or C, HBV-DNA\>2000IU/ml or 104 copy/ml; HCV-RNA\>103 copy/ml; both HBsAg and HCV antibody are positive. If the related results become lower than above standards after anti-viral treatment, the patients are qualified for enrolment; 2. Have metastasis in extrahepatic distant organs including lung, central nervous system, bone and etc. Or extrahepatic lymph node metastasis beyond abdomen; 3. Have risky bleeding events requiring transfusion, operation or local therapies, continuous medication in the past 3 months; 4. Have thromboembolism in the past 6 months, including myocardial infarction, unstable angina, stroke or transient ischemic attack, pulmonary embolism, deep vein thrombosis; 5. Have taken aspirin (\>325mg/day) or other antiplatelet drugs continuously for 10 days or more within 2 weeks before enrolment; 6. Uncontrollable hypertension, systolic pressure\>140mmHg or diastolic pressure\>90mmHg after best medical care, or history of hypertensive crisis or hypertensive encephalopathy; 7. Symptomatic congestive heart failure (NYHA class II-IV). Symptomatic or badly-controlled arrhythmia. Congenital long QT syndrome or modified QTc\>500ms upon screening; 8. Have active autoimmune diseases that require systemic treatment within 2 years before enrolment; 9. Active tuberculosis, having antituberculosis therapy at present or within 1 year; 10. Have a known history of prior invasive malignancies within 5 years before enrolment; 11. Pregnant or breastfeeding women, or expecting to conceive or father children within the projected duration of the trial; 12. Have other uncontrollable comorbidities; 13. Infection of HIV, known syphilis requiring treatment; 14. Allergic to elements of camrelizumab.