This clinical trial is focused on studying a type of liver cancer known as hepatocellular carcinoma (HCC), particularly in patients who are at high risk of the cancer returning after they have had surgery or a procedure called ablation to remove the cancer. The study is testing a combination of two medications, atezolizumab and bevacizumab, to see if they can help prevent the cancer from coming back. Atezolizumab is also known by its code name, RO5541267, and is an antibody that helps the immune system fight cancer. Bevacizumab is another antibody that works by stopping the growth of blood vessels that feed tumors.

The purpose of the study is to compare the effectiveness of the combination of atezolizumab and bevacizumab with a group of patients who will be under active surveillance, meaning they will be closely monitored without receiving the study medications. The study will last for up to 12 months, during which participants will receive the medications through an intravenous (IV) infusion, which means the medicine is given directly into a vein. The study will track how long patients remain free from cancer recurrence and will also monitor overall survival rates and any side effects experienced by participants.

Participants in the study will have regular check-ups and tests to monitor their health and the status of their cancer. The study aims to provide valuable information on whether the combination of atezolizumab and bevacizumab can be an effective treatment option for preventing the return of hepatocellular carcinoma in patients who have already undergone surgery or ablation. This research could potentially lead to new treatment strategies for managing this type of liver cancer.