S1196
Clinical - Urology
ESTRO 2026
respectively, and 57.6% and 6.1% for genitourinary. No grade 3 or above late toxicity was observed. Genitourinary toxicities were mainly driven by early events occurring in the initial 6 months following SBRT, and the proportions reduce substantially thereafter (Figure A). Similar patterns were observed in patient- reported outcomes, with transient deterioration in EPIC urinary irritative obstructive and sexual subdomains, and IPSS, in the initial 6 months (Figures B and C). EQ-5D-5L HRQOL was maintained over time. Rapid PSA responses were observed, with an estimated 100% of patients achieving PSA50 at 12 months, and PSA90 at 24 months (Figure D).
Conclusion: Prostate cancer SBRT with peri-rectal spacer results in limited early toxicity, in particular gastrointestinal, and impact on HRQOL. These institutional outcomes provide real-world evidence to support this approach. References: 1) van As N, Griffin C, Tree A, et al. Phase 3 Trial of Stereotactic Body Radiotherapy in Localized Prostate Cancer. N Engl J Med. 2024 Oct 17;391(15):1413- 1425.2) Hamstra DA, Mariados N, Sylvester J, et al. Continued Benefit to Rectal Separation for Prostate Radiation Therapy: Final Results of a Phase III Trial. Int J Radiat Oncol Biol Phys. 2017 Apr 1;97(5):976-985.3) Mariados NF, Orio PF 3rd, Schiffman Z, et al. Hyaluronic Acid Spacer for Hypofractionated Prostate Radiation Therapy: A Randomized Clinical Trial. JAMA Oncol. 2023 Apr 1;9(4):511-518. Keywords: Prostate cancer, SBRT, patient-reported outcomes Proffered Paper 1835 Prostate Radiotherapy In high-risk and N+ disease comparing Moderate and Extreme hypofractionation (PRIME trial, NCT03561961): Acute and 1-year Safety Vedang Murthy 1 , Priyamvada Maitre 1 , Moses Arunsingh 2 , Maneesh Singh 1 , Parth Verma 1 , Reena
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