Adaptive RADiation Therapy With Concurrent Sacituzumab Govitecan (SG) for Muscle Invasive Bladder Cancer

The purpose of this study is to examine the safety and tolerability of treatment with concurrent Sacituzumab Govitecan (SG) and adaptive radiation therapy. The main objective is to establish the safety, tolerability, and feasibility of bladder preservation therapy treatment with concurrent SG and adaptive image-guided radiation therapy for participants with localized MIBC. Participants will receive the study drug, SG, through an IV once weekly on days 1 and 8 of each 21-day treatment cycle. The first cycle of SG will begin 21 days prior to the scheduled start of radiation therapy. The second and third cycles of SG will be given while the participant is receiving radiation therapy. Participants will be asked to undergo computed tomography (CT) and magnetic resonance imaging (MRI) pre-and post-treatment. Participation in the research will last up to 5 years, depending on treatment outcomes, with a treatment period of 8 weeks and a study follow-up period of up to 2-5 years thereafter, and a survival follow-up, with only phone call communication from years 3-5.