S1285
Clinical - Urology
ESTRO 2026
Hospital, Nedlands, Australia. 8 Radiation Oncology, Genesis Care, Footscray, Australia. 9 Radiation Oncology, Western Sydney Local Health District, Sydney, Australia. 10 Radiation Oncology, Royal Adelaide Hospital, Adelaide, Australia. 11 Radiation Oncology, Radiation Oncology Princess Alexandra Hospital Raymond Terrace, Brisbane, Australia. 12 Radiation Oncology, Royal Hobart Hospital, Hobart, Australia. 13 Radiation Oncology, Auckland Radiation Oncology, Auckland, New Zealand Purpose/Objective: There is limited data on the use of salvage local therapy for locally recurrent prostate cancer after previous definitive radiotherapy. We aimed to evaluate the contemporary patterns of practice of stereotactic ablative body radiotherapy (SABR) for intraprostatic recurrence among Radiation Oncologists (ROs) across Australia and New Zealand (ANZ). Material/Methods: This is a cross-sectional survey (7 July 2025-10 August 2025) among ROs identified via the bi-national RANZCR Faculty of Radiation Oncology Genitourinary Group (FROGG) membership mailing list. The survey consisted of patient selection criteria and staging, ADT use, contouring, treatment planning, and treatment delivery (dose and fractionation) in patients with locally recurrent prostate cancer. Descriptive statistics were used to summarise the survey results. Results: A total of 41 ROs from 37 institutions responded to the survey (22% response rate), with representation from all ANZ jurisdictions, metropolitan/regional and public/private centres. There were 35/41 (85%) ROs who would offer, or refer, patients for prostate re- irradiation. The preferred salvage radiotherapy modalities included: SABR (26/35, 74%), HDR brachytherapy (18/35, 51%), conventionally/moderately hypofractionated external beam radiotherapy (6/35, 17%), and LDR brachytherapy (5/35, 14%). Among these, 15/35 (43%) offered prostate SABR re-irradiation in their department, and 3/15 (20%) do so only within a clinical trial setting. Most ROs would consider prostate re- irradiation in individuals with life expectancy >5–10 years (94%) and ≥ 2 years after prior radiotherapy (87%). 69% of ROs would not offer prostate re- irradiation if prior grade ≥ 3 GU/GI toxicity.All ROs reported restaging with PSMA PET/CT and MRI prior to prostate re-irradiation. Biopsy confirmation was required by 87%, with majority favouring targeted and whole gland biopsy. Concomitant ADT use varied, with 33% used it routinely and 47% used it selectively. Rectal spacers were used routinely by one-third of ROs and selectively by 53%. Focal treatment of the intraprostatic recurrence-only was most common (80%), while 20% would treat the whole-gland plus
boost. Planning target volume expansions varied between 0 and 4mm. 5-fraction schedule was most common (93%), delivered over 1 (40%), 2-3 (87%) and 5 (7%) fractions per week. Dose prescriptions ranged 30–35 Gy in 5 fractions to the intraprostatic recurrence and 23.75-25 Gy in 5 fractions to the whole gland, while a dose of 36 Gy in 6 fractions was also used. Conclusion: This is the first ANZ survey on prostate SABR re- irradiation for locally recurrent prostate cancer, suggesting an increasing interest in re-irradiation in this group of patients. Keywords: prostate, SABR, reirradiation Correlation between Qualitative Distribution of Hydrogel Spacer, Rectal Dosimetry and Adverse Events in Prostate Stereotactic Radiotherapy Francesco Salaroli 1 , Federico Colombo 1 , Marco Galaverni 1 , Michele Maddalo 2 , Francesco Ziglioli 3 , Claudia Grondelli 1 , Cristina Dell'Anna 1 , Ilaria Renna 1 , Maria Luisa Bergamini 1 , Giovanni Ceccon 1 , Elisabetta Lattanzi 1 , Stella Gianni 1 , Carmelinda Manna 4 , Giulio Negrini 4 , Livia Ruffini 5 , Umberto Vittorio Maestroni 3 , Caterina Ghetti 2 , Nunziata D'Abbiero 1 , Nicola Simoni 1 1 Department of Radiation Oncology and Radiosurgery, University Hospital of Parma, Parma, Italy. 2 Medical Physics Unit, University Hospital of Parma, Parma, Italy. 3 Urology Department, University Hospital of Parma, Parma, Italy. 4 Scienze Radiologiche, Department of Medicine and Surgery (DiMeC), University of Parma, Parma, Italy. 5 Nuclear Medicine Division, University Hospital of Parma, Parma, Italy Purpose/Objective: To assess the correlation between hydrogel rectal spacer (HRS) qualitative distribution and rectal dosimetry and acute side effects, in patients treated with Stereotactic Body Radiation Therapy (SBRT) for localized prostate cancer (PCa). Material/Methods: This analysis included patients with localized PCa who had undergone transperineal HRS placement and were treated with SBRT at our Institution as part of a prospective observational study. Hydrogel qualitative distribution using Spacer Quality Score (SQS), Digital Poster 3974 Symmetry Score (SYM), and Rectal Wall Infiltration Score (RWI) were assessed on post-implant T2- weighted magnetic resonance (MR). Correlation with rectal dosimetry and acute rectal adverse events (occurring <6 months from SBRT) was evaluated. Results: From 2022 to 2024, 76 patients with localized PCa received HRS implant prior to SBRT. Planning Target Volume (PTV) dose prescription was 36.25 Gy/5
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