BladdEr Full OR Empty for Pelvic Radiation Therapy

Pelvic radiation therapy plays a key role in the treatment of common genitourinary (GU), gynecological (Gyn), and gastrointestinal (GI) malignancies of the pelvis. Prior to starting a course of radiation therapy, patients undergo a CT simulation that allows for computer-based optimization of radiation dose delivery to target while simultaneously minimizing dose to surrounding normal tissues, such as the bladder and rectum. Commonly, physicians instruct patients undergoing pelvic radiation therapy to present with a reproducibly full bladder for the simulation and for each subsequent treatment session with the hope that increased distance between normal tissues (anterior bladder wall and bowel) and treatment target will limit toxicity. However, treating with a full bladder can result in wide variations in bladder volume. Often patients are unable to reproduce the bladder distention achieved at simulation, especially as typical urinary symptoms related to radiation develop during treatment. As the initial CT simulation is used to calculate dose distribution, bladder volume changes can affect radiation dose distribution to the bladder itself as well as adjacent pelvic organs. Given the challenges and uncertainties of treating with a full bladder, there has been increasing interest in bladder empty protocols. Retrospective, non-randomized, single-institution studies demonstrate that bladder empty protocols reduced absolute variation in bladder volume during treatment, had minimal impact on treatment related toxicity, and had non-inferior biochemical progression free survival, GI toxicities, and GU toxicities. However, prospective data is very limited. The present study plans to fill this knowledge gap by randomizing study participants to empty and full bladder protocols for simulation and radiation therapy.