ESTRO 2025 - Abstract Book

S1962

Clinical - Urology

ESTRO 2025

References: 1. Siva S, Bressel M, Sidhom M, et al. Stereotactic ablative body radiotherapy for primary kidney cancer (TROG 15.03 FASTRACK II): a non-randomised phase 2 trial. The Lancet Oncology. 2024;25(3):308-16. 2. Mariados NF, Orio PF, III, Schiffman Z, et al. Hyaluronic Acid Spacer for Hypofractionated Prostate Radiation Therapy: A Randomized Clinical Trial. JAMA Oncology. 2023;9(4):511-8. 3. Tang Q, Zhao F, Yu X, et al. The role of radioprotective spacers in clinical practice: a review. Quant Imaging Med Surg. 2018;8(5):514-24. 4. Gejerman G, Goldstein MM, Chao M, et al. Barrigel Spacer Injection Technique. Practical Radiation Oncology. 2024;14(1):e57-e61.

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Proffered Paper Preliminary results of a phase II randomized control trial of neurovascular-sparing SAbR in localized prostate cancer [PCa] (POTEN-C, NCT03525262) Neil B Desai 1 , Robert T Dess 2 , Raquibul Hannan 1 , Kevin L Stephans 3 , Tyler P Robin 4 , Alexander Slade 5 , John C Christodouleas 6 , Rahul D Tendulkar 3 , Daniel E Spratt 7 , Aurelie Garant 1 , William C Jackson 2 , Daniel X Yang 1 , Arun Goel 6 , Anthony Wong 8 , Christian Gonzalez 1 , Kimberly Zepeda 1 , Sarah Neufeld 1 , Chul Ahn 9 , Daniel N Costa 1 , Yulong Yan 1 , MinJae Lee 9 , Robert D Timmerman 1 1 Radiation Oncology, University of Texas Southwestern, Dallas, USA. 2 Radiation Oncology, University of Michgian, Ann Arbor, USA. 3 Radiation Oncology, Cleveland Clinic Taussig Cancer Institute, Cleveland, USA. 4 Radiation Oncology, University of Colorado School of Medicine, Denver, USA. 5 Radiation Oncology, Stony Brook Cancer Center, Stony Brook, USA. 6 Radiation Oncology, University of Pennsylavania, Philadelphia, USA. 7 Radiation Oncology, University Hospitals Seidman Cancer Center Case Western University, Cleveland, USA. 8 Radiation Oncology, University of California San Francisco, San Francisco, USA. 9 Public Health, University of Texas Southwestern, Dallas, USA Purpose/Objective: To report 3-month toxicity/quality of life (QoL) results from a prospective trial of neurovascular-sparing SAbR (NV SAbR) in PCa. Material/Methods: This phase II multicenter randomized-control trial enrolled men with localized PCa, intact sexual function by Expanded Prostate Cancer Index Composite (EPIC) QoL instrument, and eligibility for NV-SAbR without ADT according to MRI-disease distribution and adequate hydrogel spacer. Randomization was patient-blinded 1:1 to NV SAbR vs standard SAbR to 40Gy or 45Gy/5fx. NV-SAbR spared one side NV using dose-painting to 30Gy with central QA 1 . We hypothesized a 10-point lesser 2-year decline in EPIC sexual score (120 patient sample for 80% power at 0.1 significance level,15% attrition). Secondary endpoints included short-form EPIC-26 urinary/bowel scores and physician-reported CTCAEv4.0 GU/GI toxicities. Comparisons were made by Chi-square test for categorical variables and by t -test and Wilcoxon rank-sum test for normal and non-normal continuous variables, respectively. Significance level was set at p=0.05 for comparisons beyond primary sexual domain. Results: Of 120 men randomized, 118 (59/arm) were evaluable at 3 months. 3-month toxicities did not significantly differ (p>0.1) between standard vs NV-SAbR (p>0.1): GU (Grade 1: 53% vs 49%, Grade 2: 17% vs 27%), GI (Grade 1: 17% vs 24%, Grade 2: 3% vs 5%). For EPIC QoL at 3-months ( Table 1 ), NV-SAbR vs standard SAbR was associated with significantly better score for urinary irritative/obstructive domain (mean 91 vs 86; median [interquartile range, IQR]: 94 [88, 100] vs 94 [75, 94], Wilcoxon p=0.02) and with improved sexual domain score at the boundary of pre-defined significance level (mean 71 vs 67; median [IQR]: 75 [60, 85] vs 69 [57, 81], Wilcoxon p=0.10). Similarly, NV-SAbR demonstrated smaller mean