S1231
Clinical - Urology
ESTRO 2026
change). A decreasing bowel bother score of >20 points in relation to baseline at the last day of RT was defined as a severe acute bowel function change and the relevance for late changes was evaluated for patients treated with or without a spacer. A negative change corresponds to improving quality of life. Results: Patients without severe acute changes remained without clinically relevant mean bowel bother changes with and without a spacer two months (-1 vs. 1 point) and 1-2 years after RT (-1 vs. 4 points), respevtively. Severe acute bowel bother changes in relation to baseline scores were reported by 31% and 37% of patients with and without a spacer, respectively (not significant). Mean bowel bother score changes in this subgroup were similar for patients with vs. without a spacer at the end of RT (40 vs. 41 points) and two months after RT (14 vs. 16 points). However, mean bowel bother score changes 1-2 years after RT were significantly lower for patients with a spacer (4 vs. 17 points; p=0.03), remaining below a clinically relevant difference. Conclusion: The application of a spacer had no relevant effect on acute bowel bother score changes during and shortly after prostate cancer radiotherapy. However, in contrast to patients without a spacer, these acute changes were reversible with significantly smaller differences in comparison to baseline scores. The impact of consequential late effects was reduced significantly by the spacer. Keywords: prostate neoplasm; spacer; quality-of-life Digital Poster 2496 Efficacy and Toxicity of SBRT Reirradiation for Locally Recurrent Prostate Cancer: A Single-Center Experience Ahmed Abdelmaqsoud, Georgios Skazikis, Omar Habibeh, Mariam Zurabashvili, Stephan Mose Radiotherapy, Schwarzwald-Baar Klinikum, Villingen- Schwenningen, Germany Purpose/Objective: The aim of this retrospective study was to evaluate the efficacy of SBRT reirradiation for locally recurrent prostate cancer in terms of biochemical response, toxicity profile, and treatment failure. Material/Methods: we collected data on all patients treated at our CyberKnife center for locally recurrent prostate cancer using SBRT. Inclusion criteria included patients with prostate cancer who had previously undergone radiotherapy, whether as definitive or salvage treatment. Local recurrence was confirmed by both biochemical recurrence and a metabolically active
IMRT/VMAT with HDRb, demonstrating toxicity and quality-of-life outcomes comparable to CF while substantially shortening treatment duration. These results establish a strong safety foundation supporting UHF as a viable, patient-centered alternative for high- risk prostate cancer requiring elective nodal irradiation. The upcoming, final non-inferiority analysis will determine long-term equivalence in efficacy and thus inform guideline-level adoption. References: 1. Widmark, A. et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. The Lancet394, 385–395 (2019).2. Mendez, L. C. et al. Is Ultrahypofractionated Whole Pelvis Radiation Therapy (WPRT) as Well Tolerated as Conventionally Fractionated WPRT in Patients With Prostate Cancer? Early Results From the HOPE Trial. Int. J. Radiat. Oncol. Biol. Phys.119, 803–812 (2024).3. Fabi, F. et al. 2249 Pelvic ultra-hypofractionated vs conventionally fractionated IMRT with HDR brachytherapy boost in prostate cancer: PCS-XI trial interim (NCT05820633).
Radiother. Oncol.206, S1992–S1994 (2025). Keywords: HDR Brachytherapy, Prostate, Hypofractionation
Digital Poster 2478
Impact of the hydrogel spacer on consequential late effects after radiotherapy for prostate cancer Michael Pinkawa 1,2 , Marsha Schlenter 2 , Liane König 2 , Michael J. Eble 2 1 Radiation Oncology, WEGE Klinik, Bonn, Germany. 2 Radiation Oncology, RWTH Aachen University, Aachen, Germany Purpose/Objective: Acute effects of radiotherapy (RT) can progress to late effects as consequential late effects, if mechanical or physical stress prevents healing. It is not well known if protective factors can be applied to prevent the development of consequential late effects. Material/Methods: A group of 202 patients was treated for prostate cancer with single fractions of 2Gy up to total doses of 76-80Gy with a IMRT or VMAT technique. Depending on the patient’s and radiation oncologist’s preference, 108 patients were selected for a 10ml hydrogel injection under transrectal ultrasound guidance before the beginning of RT. Patients were surveyed prospectively before RT, at the last day of RT, a median time of two months and 1-2 years after RT using a validated questionnaire (Expanded Prostate Cancer Index Composite, transformed lineary to a 0-100 scale, with 5 points change defined as a clinically relevant
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