Bowel and bladder reproducibility in image-guided SBRT prostate: Results of a patterns of practice survey.

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76 Background: Use of prostate stereotactic body radiotherapy (SBRT) as treatment for localized prostate cancer (PCa) is increasing. Given the high dose (>5Gy) per fraction (Fx) being delivered, SBRT requires careful preparation and delivery to ensure accuracy and precision. Guidelines and data on best practice for bowel and bladder preparation are lacking. Therefore, we surveyed practicing radiation oncologists (RO) to document practice patterns for prostate SBRT. Methods: From June to October 2018 we completed a nationwide survey of 1395 American Society for Therapeutic Radiology and Oncology (ASTRO) members who self-identified as managing PCa. A SurveyMonkey link was sent via email, and analysis included practicing RO who treat PCa with SBRT. Results: 204 responses were received with 32% (64/204) using SBRT. 80% (51/64) provided the fractionation used: 33% (17/51) use 35Gy to 36.25Gy, and 17.6% (9/51) use >40Gy in 5 Fx, and 1 used >9Gy Fx. 94% use implantable devices for localization (83% fiducial markers, 17% radiofrequency transponders). 65% (42/64) use a hydrogel spacer. 75% (48/64) use daily cone beam CT (CBCT) for image guidance. The majority use a 5 mm PTV, with 3 mm posteriorly. For bladder and bowel preparation 97% (62/64) provided preferences. For bladder, 90.3% (56/62) required a comfortably full bladder for both simulation and treatment. For simulation, 92% (57/62) have a bowel protocol (BP) to optimize rectal reproducibility. 51.6% (31/62) have patients empty their bowels prior, and 51.6% (31/62) prescribe a BP. Diet alteration was recommended by 77% (48/62). 86% (53/62) used a BP during SBRT treatment. Of those using a BP, 67% (43/64) continued it throughout SBRT with 30% (19/64) continuing BP unless symptoms change management. Only 3% (2/64) stop BP after simulation. Conclusions: The variability of data in the literature on effective BP for treatment reproducibility for PCa is reflected in the varied patterns of practice seen in our survey. Consensus on bladder preparation is seen for a majority of practitioners. A variety of BP regimens are employed.