Radiation Therapy and Durvalumab, With or Without Tremelimumab, in Patients With Bladder Cancer

All participants will receive durvalumab 1500 mg via IV infusion every 4 weeks for up to 13 doses.

Participants receiving Regimen B (safety lead-in or expansion cohort) will be administered tremelimumab 75 mg via IV infusion every 4 weeks for 1 cycle or 2 cycles.

In all arms of the study, participants will receive 5 fractions of radiation. The radiation dose will either be 6.6 Gy for a total dose of 33 Gy, or 6.0 Gy for a total dose of 30 Gy.