This study will evaluate the efficacy and safety of atezolizumab plus bevacizumab combined with on-demand TACE compared to on-demand TACE alone in participants with hepatocellular carcinoma who are at high risk of poorer outcome following TACE treatment.

Inclusion Criteria:

• Confirmed diagnosis of HCC by histology/ cytology or clinical criteria
• Eligible for TACE treatment
• No prior systemic therapy for HCC, especially immunotherapy
• No prior locoregional therapy to the target lesion(s)
• At least one measurable untreated lesion
• ECOG Performance Status of 0-1
• Child-Pugh class A

Exclusion Criteria:

• Evidence of Vp3/4 and hepatic vein tumor thrombus (HVTT)
• Evidence of extrahepatic spread (EHS)
• Being a candidate for curative treatments
• Any condition representing a contraindication to TACE as determined by the investigators
• Active or history of autoimmune disease or immune deficiency
• Untreated or incompletely treated esophageal and/or gastric varices with bleeding or high risk for bleeding
• A prior bleeding event due to esophageal and/or gastric varices within 6 months prior to initiation of study treatment
• Evidence of bleeding diathesis or significant coagulopathy

For eligible studies, qualified researchers may request access to individual patient level clinical data. See Roche's commitment to transparency of clinical study information here: https://go.roche.com/data\_sharing