Chemoradiotherapy With or Without Atezolizumab in Treating Patients With Localized Muscle Invasive Bladder Cancer

This phase III trial studies how well chemotherapy and radiation therapy work with or without atezolizumab in treating patients with localized muscle invasive bladder cancer. Radiation therapy uses high energy rays to kill tumor cells and shrink tumors. Drugs used in chemotherapy, such as gemcitabine, cisplatin, fluorouracil and mitomycin-C, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving chemotherapy with radiation therapy may kill more tumor cells. Immunotherapy with monoclonal antibodies, such as atezolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving atezolizumab with radiation therapy and chemotherapy may work better in treating patients with localized muscle invasive bladder cancer compared to radiation therapy and chemotherapy without atezolizumab.