Urinary Organs-at-Risk for Radiation Therapy Following Radical Prostatectomy: Contouring Guidelines on Behalf of the Francophone Group of Urological Radiation Therapy (GFRU).

PURPOSE: Urinary toxicity following radical prostatectomy (RP) and postoperative radiation therapy (RT) includes urinary incontinence and vesicourethral anastomosis strictures. With the increasing use of stereotactic body RT (SBRT), dose escalation, and reirradiation of the prostate bed (PB), standardization of the definition of urinary organs-at-risk (OARs) in the post-RP setting is needed. This work aimed to provide a comprehensive review of the anatomic and physiopathological changes occurring after RP, as well as a consensus on urinary OAR delineation for prostate cancer external beam RT in the post-RP setting.

METHODS AND MATERIALS: A multidisciplinary task force, comprising 3 radiation oncologists, 1 uroradiologist, and 2 urologists, was created in 2024. First, OARs potentially involved in urinary toxicity were identified and discussed. A literature review was performed, addressing several questions relative to surgical procedures and reconstructive strategies. A focus was also given to potential complications following RP and its impact on urinary OARs. Second, results were presented and discussed with a panel of radiation oncologists, members of the "Francophone Group of Urological Radiation Therapy." Thereafter, the Francophone Group of Urological Radiation Therapy experts were asked to answer a dedicated questionnaire, including 26 questions on the controversial issues related to the delineation of urinary OARs.

RESULTS

The following structures were identified as critical for RT in the post-RP setting: bladder, bladder neck, bladder trigone, vesicourethral anastomosis, membranous urethra, and striated sphincter. A consensus was reached for 25 out of 26 items.

CONCLUSIONS

New clinical scenarios at risk of toxicity in the post-RP setting are emerging, including especially PB reirradiation with SBRT, PB SBRT, and dose-escalated RT to the PB. This consensus highlights contemporary urinary structures in the post-RP setting. It also proposes a standardized definition of urinary OARs for the development of future clinical trials.