The present study evaluates empty and full bladder protocols for radiation therapy of genitourinary (GU), gynecological (Gyn), and gastrointestinal (GI) malignancies of the pelvis.

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.

Inclusion Criteria:

• Provision of signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Persons, aged at least 18 years
• Deemed eligible to undergo curative intent radiation therapy for primary GU, GI, or Gyn malignancy of the pelvis.
• For participants able to become pregnant: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation
• For participants able to cause a pregnancy: use of condoms or other methods to ensure effective contraception with partner

Exclusion Criteria:

• Pregnancy
• Tumor invading the bladder, as judged by the enrolling physician based on available clinical information
• Contraindications to radiotherapy, including Crohn's disease and active connective tissue disorders such as scleroderma or uncontrolled lupus
• Prior radiation therapy to an area requiring treatment in the present study

There is not a plan to make individual participant data (IPD) available