Urinary Organs at Risk for Prostate Cancer External Beam Radiation Therapy: Contouring Guidelines on Behalf of the Francophone Group of Urological Radiation Therapy

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PurposeOccurrence of genitourinary (GU) toxicity is a common adverse event observed after external beam radiotherapy (EBRT) for prostate cancer (PCa). Recent findings suggest that the dose delivered to specific urinary organs-at-risk (OARs) such as ureters, bladder trigone, and urethra is involved in the development of GU toxicity. Methods and materialsA multidisciplinary task force including three radiation oncologists, a uroradiologist, and a urologist was created in 2022. First, OARs potentially involved in GU toxicity were identified and discussed. A literature review was performed, addressing several questions relative to urinary OARs: anatomical and radiological definition, radiation-induced injury, dose-volume parameters. Secondly, results were presented and discussed with a panel of radiation oncologists, members of the “Francophone Group of Urological Radiation Therapy” (GFRU). Thereafter, GFRU experts were asked to answer a dedicated questionnaire, including 35 questions on the controversial issues related to the delineation of urinary OARs. ResultsThe following structures were identified as critical for PCa EBRT: ureters, bladder, bladder neck, bladder trigone, urethra (intraprostatic, membranous, spongious), striated sphincter, and post-enucleation or post-transurethral resection of the prostate (TURP) cavity. A consensus was obtained for 32 out of 35 items. ConclusionThis consensus highlights contemporary urinary structures in both upper and lower urinary tract to be considered for EBRT treatment planning of PCa. The current recommendations also propose a standardized definition of urinary OARs, for both daily practice and future clinical trials.