This study intends to evaluate the efficacy and safety of hepatic arterial infusion chemotherapy of oxaliplatin, 5-fluorouracil and leucovorin plus lenvatinib and Sintilimab for patients hepatocellular carcinoma and portal vein tumor thrombus.

Hepatic arterial infusion chemotherapy (HAIC) of oxaliplatin, 5-fluorouracil and leucovorin was effective and safe for hepatocellular carcinoma. Lenvatinib was non-inferior to sorafenib in overall survival in untreated advanced hepatocellular carcinoma, and Sintilimab, an programmed cell death protein-1 (PD-1) antibody, was effective and tolerable in patients with hepatocellular carcinoma and portal vein tumor thrombus. No study has evaluated HAIC plus Lenvatinib and Sintilimab. Thus, the investigators carried out this prospective, single-arm study to find out it.

Inclusion Criteria:

• 1. clinical diagnosis of HCC; 2. age between18 and 75 years; 3. refused to sorafenib treatment; 4. type I PVTT, type II PVTT, or type III PVTT. 5. Child-Pugh class A or B; 6. Eastern Cooperative Group performance status (ECOG) score of 0-2; 7. Hemoglobin ≥ 8.5 g/dL Total bilirubin ≤ 30mmol/L Serum albumin ≥ 32 g/L ASL and AST ≤ 5 x upper limit of normal Serum creatinine ≤ 1.5 x upper limit of normal INR ≤ 1.5 or PT/APTT within normal limits Absolute neutrophil count (ANC) >1,500/mm3 8. Prothrombin time ≤18s or international normalized ratio < 1.7. 9. Ability to understand the protocol and to agree to and sign a written informed consent document.

Exclusion Criteria:

• 1. Diffuse HCC; 2. Extrahepatic metastasis; 3. Obstructive PVTT involving both the left and right portal vein or main portal vein.

  4. Serious medical comorbidities. 5. Evidence of hepatic decompensation including ascites, gastrointestinal bleeding or hepatic encephalopathy 6. Known history of HIV 7. History of organ allograft 8. Known or suspected allergy to the investigational agents or any agent given in association with this trial.

  9. Cardiac ventricular arrhythmias requiring anti-arrhythmic therapy 10. Evidence of bleeding diathesis. 11. Patients with clinically significant gastrointestinal bleeding within 30 days prior to study entry.