Atezolizumab plus Bevacizumab combination therapy (AtezoBev) is well-known 1st-line therapy for advanced hepatocellular carcinoma (HCC). However, there are unmet needs for patients with advanced HCC who do not respond to AtezoBev. External beam radiotherapy (RT) is another well-known locoregional therapy for HCC that induces inflammatory cascade and abscopal effect as a systemic anticancer effect and enhances the effect of AtezoBev. Therefore, the investigators aim to verify the effect of AtezoBev plus RT for advanced HCC through this single-center, prospective phase II one-armed cohort study over three years. This study recruits 51 patients to verify the effect of the intervention. Atezolizumab (1200mg) and Bevacizumab (15mg/kg) are administered to patients once for each cycle at 3-week intervals, and additional radiotherapy for the mass or portal vein tumor thrombosis is performed before second cycle of AtezoBev. The primary endpoint is progression-free survival by using response evaluation with modified RECIST.

Inclusion Criteria:

1. age ≥19;
2. clinically or histologically diagnosed HCC;
3. HCC with Vp2-Vp4 portal vein invasion;
4. intact liver function with Child-Pugh class A;
5. adequate size of RT field;
6. intact performance with ECOG below 2;
7. non-pregnant with acceptable contraception in premenopausal women);
8. without other life-threatening diseases;
9. ability to provide written informed consent and to comply with all study conditions.

Exclusion Criteria:

1. Active uncontrolled infection;
2. Current or history (< or = 5 years) of advanced malignancies in the other organs;
3. History of liver transplantation;
4. miliary HCC which incompatible external beam RT