This clinical trial is focused on studying high-risk muscle-invasive bladder cancer, a type of cancer that affects the bladder and can spread to other parts of the body. The study is investigating the effects of a treatment called atezolizumab, which is a type of medication known as an anti-PD-L1 antibody. This medication is designed to help the immune system recognize and fight cancer cells more effectively. The trial will compare the effects of atezolizumab with a placebo in patients who have undergone surgery to remove the bladder cancer and are found to have circulating tumor DNA (ctDNA) in their blood, which indicates a higher risk of cancer returning.

The purpose of the study is to evaluate how well atezolizumab works in preventing the return of cancer in these patients. Participants in the study will receive either atezolizumab or a placebo through an intravenous infusion, which means the medication is given directly into a vein. The study will monitor patients over a period of time to assess their disease-free survival, which refers to the length of time patients remain free from cancer after treatment. The study will also look at other factors, such as overall survival and the presence of any side effects from the treatment.

Throughout the study, patients will have regular check-ups and tests to monitor their health and the status of their cancer. These tests may include blood tests to check for ctDNA and other markers, as well as imaging tests to look for any signs of cancer returning. The study aims to provide valuable information on the effectiveness of atezolizumab as an additional therapy for patients with high-risk muscle-invasive bladder cancer, potentially offering a new option for preventing cancer recurrence in this group of patients.