S1238
Clinical - Urology
ESTRO 2026
experiencing grade 2 genitourinary toxicity by 12 weeks. The focal boost may have increased toxicity over 5 fractions, offsetting any potential decrease in toxicity from whole gland de-escalation. Further studies need to establish the optimal whole gland and focal dose in five fractions. References: 1 As N van et al. Ph 3 Trial of Stereotactic Body Radiotherapy in Localized Prostate Cancer. NEJM. 2024;391:1413–25. 2 Tree AC, et al. Intensity- modulated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): 2-year toxicity results from an open-label, randomised, phase 3, non-inferiority trial. Lancet Oncol. 2022;23:1308– 20. 3 Winkel D, et al. Adaptive radiotherapy: The Elekta Unity MR-linac concept. CTRO. 2019;18:54– 9. 4 Tocco BR, et al. MR-Guided Radiotherapy for Prostate Cancer. Fr Onco. 2020;10:616291. 5 Dunlop A, et al. Daily adaptive radiotherapy for patients with prostate cancer using a high field MR-linac: Initial clinical experiences and assessment of delivered doses. CTRO 2020;23:35–42. Keywords: de-escalation, SBRT, prostate radiotherapy Evaluating the Impact of Complete Response After Oligometastasis-Directed SBRT in Prostate Cancer: A Multi-Institutional Experience Andrea D'Aviero 1 , Donato Pezzulla 2 , Marco Lucarelli 3 , Giulia de Pasquale 4 , Tamara Santone 4 , Paolo Bonome 5 , Milena Ferro 5 , Antonietta Augurio 4 , Annamaria Vinciguerra 4 , Gabriella Macchia 5 , Francesco Deodato 5 , Domenico Genovesi 1 1 Department of Medical, Oral and Biotechnological Sciences, "G. D’Annunzio” University of Chieti - Pescara, Chieti, Italy. 2 Radiation Oncology Unit, Responsible Research Hospital, Chieti, Italy. 3 Division of Radiation Oncology, European Institute of Oncology IRCSS, Milan, Italy. 4 Department of Radiation Oncology, "S.S. Annunziata" Chieti Hospital, Chieti, Italy. 5 Radiation Oncology Unit, Responsible Research Hospital, Campobasso, Italy Purpose/Objective: Stereotactic Body Radiotherapy (SBRT) has emerged as a validated treatment option for prostate cancer oligometastases, offering excellent local control, minimal toxicity, and strong patient compliance. This multi-institutional study aimed to assess the impact of achieving a complete response (CR) on clinical outcomes in patients treated with SBRT for prostate oligometastatic disease. Material/Methods: We retrospectively reviewed data from 155 prostate Digital Poster 2724
DESTINATION is a prospective, phase II, non- randomised federated study that enrolled men with localised prostate cancer across three institutions (The Royal Marsden Hospital, Sunnybrook Health Sciences Centre, and The Netherlands Cancer Institute). Patients received MR-guided SBRT delivered on the MR-linac with daily online replanning. [5]The treatment regimen consisted of 30 Gy in 5 fractions to the whole prostate with no margin. The dominant lesion plus a 4mm margin received 45 Gy in 5 fractions. An example plan is shown in figure 1. Acute toxicity was assessed using CTCAEv5 at baseline, end of treatment, 4 weeks, and 12 weeks post-treatment. Patient-reported outcomes were collected using IPSS, EPIC-26 and IIEF5 questionnaires. Results: All 60 patients completed 12-weeks follow-up. Grade 2 genitourinary toxicity was seen in 55% of patients by 12 weeks, with the greatest rate of symptom change occurring between baseline and the last fraction. Just over 10% of patients experienced acute grade 2 gastrointestinal toxicity. Patient-reported outcomes demonstrated the expected flare in symptoms at the last fraction of treatment followed by gradual recovery. Notable patterns included consistently higher EPIC summary and domain scores at NKI compared to RMH/Sunnybrook, with sexual function decline during follow-up for all centres. Conclusion: The DESTINATION study demonstrates that dose de- escalation 5-fraction SBRT with focal boost produces acute toxicity rates similar to or above the levels seen in the PACE-B trial, with just over half of the patients
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