ESTRO 2025 - Abstract Book

S2114

Clinical - Urology

ESTRO 2025

Patients were excluded if they: • Received any prior pelvic radiotherapy • Received prostate and nodal SABR simultaneously • Did not have a hydrogel spacer implanted

The RTOG acute grading was recorded at the last fraction and 6-8 weeks post treatment; RTOG late scale was used at the 6 months, 1 year and 2-year follow-up visit. The worst grade of RTOG rectal toxicity was recorded.

Results: 113 patients were evaluated, and the Median PSA was 7.3ng/mL (IQR 4.0). Most patients (79%) had Gleason score adenocarcinoma 3+4=7 (n=89); 7% (n=8) had Gleason 4+3=7, 11% (n=13) with Gleason 3+3=6 and 2% (n=3) with Gleason 8 disease. Median prostate volume was 35cc (IQR 19.75cc). Median rectal D1cc, D2cc and V50% were 29.77Gy (IQR 5.25Gy), 27.29Gy (IQR 4.83y) and 6.8cc (IQR 4.3cc) respectively 81% patients experienced no gastrointestinal toxicity on finishing SABR (N=92), 16% (n=18) reported grade 1, and 3% patients (n=3) experienced grade 2 of which 50% reported full resolution by 6 months. Grade 2 toxicity was <5% and the full results can be seen in figure 1. There was no grade 3 toxicity reported at any timepoint.

Conclusion: Early clinical use of the SpaceOAR Vue TM in patients undergoing prostate SABR is encouraging for extremely low rates of rectal toxicity. Longer term follow-up will determine the incidence of late rectal toxicity in this cohort. The role of SpaceOAR Vue TM is currently being examined in the international multicentre prospective phase 3 SABRE trial, NCT04905069. Keywords: Prostate, SABR, Rectal toxicity References: 1.Kennedy, Thomas A.C et al. Stereotactic Radiation Therapy for localised prostate cancer: 10-year outcomes from three prospective trials. International Journal Radiaiton Oncology, Biology, Physics. Sept 2024.