ESTRO 2025 - Abstract Book

S2096

Clinical - Urology

ESTRO 2025

solution that separate the posterior aspect of the prostate from the anterior rectal wall in attempt to reduce toxicities. SpaceOAR Vue TM hydrogel is an iodinated crosslinked PEG which make it radiopaque, so that the hydrogel can be visualized on CT. Material/Methods: 499 patients who had external beam radiotherapy at our institution for localised prostate cancer between June 2022 to May 2024 were included. SpaceOAR Vue (SPV)were inserted in 205 patients and 294 had radiotherapy without rectal spacing. Patient eligibility for SPV was assessed against robust institutional inclusion criteria. All patients had insertion of SPV under local anaesthetic by a consultant urologist. Dosimetry analyses were done during and post treatment. 50 Patients with SPV who completed a baseline 12 item PRO-CTC AE, before treatment, were subsequently followed up with the same graded questionnaire at set time points. Results: Median rectum dose was 18.26 Gy for SPV group vs 18.26 Gy SD for control group. Benefit of spacing were maintained in all rectal dose metrics and magnitude were observed more in higher dose metrics .No statistical significance was observed between spacer and control groups in bladder dose metrics, though there was numerical benefit in V35 Gy. In control group median Penile Bulb were 21.95 Gy vs 22.16 Gy respectively. Rectal spacing demonstrated reducing bowel dose to V36 Gy and V40 Gy but could not reach statistical end point due to small number of patients who had bowel contoured. In SPV group ,50% patients reported no change from baseline urinary toxicity for 6 weeks follow up and combined grade 1 and 2 GU toxicities were reported in 50% patients which improved to 24% in 6 months period with no grade 3 or above reported toxicities. Regarding GI toxicities, new ≥ frequent patient reported adverse events were diarrhoea constipation and pain on opening bowels in the first 2 months in 24% patients but were reduced significantly at 9 months follow up with grade 1 in 16% and grade 2in % patients. No patient reported frequent GI bleeding. No grade ≥4 toxicity was seen. Conclusion: Our experience has shown that SPV is safe and contributed to reduce OAR doses which is reflected by low acute and intermediate GI and GU toxicities.

Keywords: Rectal spacing, prostate cancer, QOL

References:

Xu H, Gordon JJ, Siebers JV. Coverage-based treatment planning to accommodate delineation uncertainties in prostate cancer treatment. Med Phys. 2015 Sep;42(9):5435-43. doi: 10.1118/1.4928490. PMID: 26328992; PMCID: PMC4545100. Alannah Kejda, Regina Bromley, Linda Bell, Maegan Stewart, Andrew Kneebone, Thomas Eade, George Hruby, Radiological evaluation of an iodised hydrogel for prostate radiotherapy applications, Physica Medica, Volume 114,2023,103155,ISSN 1120-1797, https://doi.org/10.1016/j.ejmp.2023.103155.

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