Combination of Sintilimab and Stereotactic Body Radiotherapy in Hepatocellular Carcinoma (ISBRT01)

Inclusion Criteria: 1. Histologically confirmed hepatocellular carcinoma or diagnosed by American Association for the Study of Liver Disease criteria; 2. No previous treatment for hepatocellular carcinoma, and received arterially directed therapy (transarterial chemoembolization or hepatic arterial infusion chemotherapy) as initial treatment and achieved technical success; 3. Absence of extrahepatic metastasis disease; 4. Portal vein invasion (at least the first- or second-branch portal vein) confirmed by 2 imaging techniques; 5. Less than 3 active intrahepatic lesions with a total diameter of less than 15 cm were required, at least one of which is measurable according to the mRECIST Criteria; 6. Age at diagnosis 18 to 75 years; 7. Eastern Cooperative Oncology Group performance status ≤ 2 8. Child-Pugh class A liver function; 9. Normal liver volume greater than 700 ml; 10. Estimated life expectancy ≥12 weeks; 11. The function of important organs meets the following requirements: a. white blood cell count (WBC) ≥ 3.0×109/L, absolute neutrophil count (ANC) ≥ 1.5×109/L; b. platelets ≥ 50×109/L; c. hemoglobin ≥ 9g/dL; d. serum albumin ≥ 2.8g/dL; e. total bilirubin ≤ 1.5×ULN, ALT, AST and/or AKP ≤ 2.5×ULN; f. serum creatinine ≤ 1.5×ULN or creatinine clearance rate \>60 mL/min; 12. Ability to understand the study and sign informed consent. Exclusion Criteria: 1. Patients who have been treated previously with systemic anti-tumor therapy (including chemotherapy, molecule-targeted therapy, immunotherapy, etc.); 2. Patients with extrahepatic metastasis disease at diagnosis; 3. The total diameter of the active intrahepatic lesions was more than 15 cm; 4. A history of abdominal radiotherapy; 5. Known or suspected allergy or hypersensitivity to monoclonal antibodies; 6. Patients who have a preexisting or coexisting bleeding disorder; 7. Female patients who are pregnant or lactating; 8. Inability to provide informed consent due to psychological, familial, social and other factors; 9. A history of malignancies other than hepatocellular carcinoma before enrollment, excluding non-melanoma skin cancer, in situ cervical cancer, or cured early prostate cancer; 10. A history of diabetes for more than 10 years and poorly controlled blood glucose levels; 11. Patients who cannot tolerate radiotherapy due to severe cardiac, lung, liver or kidney dysfunction, or hematopoietic disease or cachexia; 12. Active autoimmune diseases, a history of autoimmune diseases (including but not limited to these diseases or syndromes, such as colitis, hepatitis, hyperthyroidism), a history of immunodeficiency (including a positive HIV test result), or other acquired or congenital immunodeficiency diseases, a history of organ transplantation or allogeneic bone marrow transplantation; 13. A history of interstitial lung disease or non-infectious pneumonia; 14. A history of active pulmonary tuberculosis infection within 1 year or a history of active pulmonary tuberculosis infection more than 1 year ago but without formal anti-tuberculosis treatment; 15. Presence of active hepatitis B (HBV DNA ≥ 2000 IU/mL or 104 copies/mL), hepatitis C (positive for hepatitis C antibody, and HCV-RNA levels higher than the lower limit of the assay); 16. Any unstable situation that may endanger the safety and compliance of patients.