ESTRO 2025 - Abstract Book

S2043

Clinical - Urology

ESTRO 2025

3318

Digital Poster Perirectal space creation using an iodinated hydrogel spacer in subjects with prostate cancer receiving stereotactic body radiotherapy (SABRE Trial) Suneil Jain 1 , Danielle Vannan 2 , Erin Chaussee 2 , Sean Collins 3 , Michael Zelefsky 4 , Pierre Blanchard 5 1 Patrick G Johnston Centre for Cancer Research, Queen's University Belfast, Belfast, United Kingdom. 2 Boston Scientific Corporation, Boston Scientific Corporation, Marlborough, USA. 3 Radiation Oncology, USF Health Morsani College of Medicine, Tampa, USA. 4 Radiation Oncology, NYU Medical Center, New York, USA. 5 Radiation Oncology, Institut Gustave Roussy, Villejuif, France Purpose/Objective: Prostate stereotactic body radiotherapy (SBRT) is a standard treatment for intermediate risk prostate cancer. Clinical data suggests whole prostate dose escalation increases cancer control with increased risk of late gastrointestinal (GI) toxicity. The main objective of the SABRE trial is to demonstrate the effectiveness of a next generation radiopaque polyethylene glycol (PEG) hydrogel spacer in reducing late GI toxicity in subjects undergoing prostate SBRT (Figure 1). We present the clinical characteristics and extent of spacing in subjects enrolled to date. Safety and effectiveness outcomes will be reported separately as follow-up is completed.

Material/Methods: In this prospective, multi-center, multinational randomized controlled trial (NCT04905069), 500 planned subjects are being randomized 2:1 spacer:control. Spacer subjects receive a transperineal injection of 10 mL of the iodinated PEG hydrogel. SBRT (40 Gy in 5 fractions) is planned for all subjects. Over 5-year follow-up, subjects will be assessed for GI and GU toxicity (NCI CTCAE), quality-of-life (EQ-5D-5L and EPIC-26 questionnaires), tumor control (PSA levels), device deficiencies and concomitant medications. The primary endpoint is late grade 2+ GI toxicity (3-24 months) after SBRT with or without placement of the hydrogel spacer; adverse event cumulative incidence will be compared by study arm. Enrollment is anticipated to complete in 2025 with primary endpoint results available 24 months following SBRT initiation. Results: Subject data is reported from 26 participating sites, including 17 in Europe (UK, France, Germany, Ireland, Italy, Spain, and Switzerland), USA (6), and Australia (3). As of Sept 1, 2024, 328 subjects have been randomized and 275 (187 spacer, 88 control) have completed SBRT planning. Baseline subject characteristics do not differ between study arms (Table 1). The majority (64%) of subjects have Gleason score 3+4, and 31% have score 4+3. Approximately 46% of subjects were on hormone therapy at baseline. Median mid-gland separation post-spacer placement is 9.6mm (IQR: 7.2-11.0). 94.5% subjects have received SBRT on a linear accelerator.