S1248
Clinical - Urology
ESTRO 2026
lesion (DIL) in patients with localized prostate cancer (PCa) enrolled in the prospective PRO-SPEED trial (NCT06331013). Material/Methods: The CyberKnife Ultra-hypofractionated SBRT for Localized PROStatE cancEr (PRO-SPEED) trial is a prospective monocentric observational study conducted at the European Institute of Oncology (IEO) with a projected enrolment of 60 patients. Inclusion criteria were low-, intermediate-, or high-risk localized prostate cancer, with up to three mpMRI-defined DILs. Androgen deprivation therapy (ADT) was prescribed according to NCCN guidelines. Treatment consisted of 36.25 Gy to the entire prostate and a 40 Gy SIB to the DIL, administered in five alternate-day fractions using fiducial-based CyberKnife tracking. Adverse events were evaluated using RTOG/EORTC criteria, while patient-reported outcomes were assessed with the International Prostate Symptom Score (IPSS) and International Index of Erectile Function (IIEF-5). PSA kinetics and biochemical control were analysed as secondary endpoints. Results: Forty patients were enrolled; three were dropped-out after pre-treatment mpMRI for not meeting all inclusion criteria. Thirty-seven patients were included in the analysis. Median follow-up was 12.3 months. Most were intermediate-risk (65%), and 38% received short-course ADT. All treatment plans achieved optimal target coverage and organ-of- interest sparing. Acute grade ≥ 2 genitourinary (GU) and gastrointestinal (GI) toxicities occurred in 8.1% and 3.4% of patients, respectively. Late grade ≥ 2 GU and GI events remained ≤ 3.8% through 12 months, with no acute or late grade ≥ 3 events observed (figure 1). IPSS scores increased transiently after treatment (median 6.5 → 8) but returned to baseline by six months and slightly improved below baseline at 6–12 months (median 5–6). IIEF-5 scores declined modestly but stabilized thereafter. Median PSA decreased from 7.08 ng/mL at diagnosis (IQR: 4.61–9.06) to 0.70 ng/mL at 12 months (IQR 0.22–1.41), with no biochemical or clinical relapses observed (figure 2).
Conclusion: If salvage focal therapy is planned, an MRI-targeted biopsy alone is insufficient for prostate mapping. References: 1) Light A, Kanthabalan A, Otieno M, et al. The Role of Multiparametric MRI and MRI-targeted Biopsy in the Diagnosis of Radiorecurrent Prostate Cancer: An Analysis from the FORECAST Trial. Eur Urol. 2024 Jan;85(1):35-46. doi: 10.1016/j.eururo.2023.09.001. Epub 2023 Sep 29. PMID: 37778954.2) Venkatesulu B, Adams W, Joel R, et al. The Importance of Multiparametric Magnetic Resonance Imaging, Positron Emission Tomography/Computed Tomography, and Biopsy for Identifying and Delineating the Extent of Intraprostatic Radiorecurrent Prostate Cancer: A Secondary Analysis of the F-SHARP Clinical Trial. Int J Radiat Oncol Biol Phys. 2025 Aug 1;122(5):1186-1191. Keywords: intraprostatic recurrence, salvage SBRT, mpMRI Cyberknife UH-SBRT for localized Prostate cancer and DIL: preliminary report of acute and late side effects of the prospective PRO-SPEED trial Karl Amin 1,2 , Giovanni Carlo Mazzola 1 , Giulia Marvaso 1,2 , Stefano Durante 1 , Andrea Vavassori 1 , Federico Mastroleo 1,3 , Dario Zerini 1 , Cristiana Luliana Fodor 1 , Mattia Zaffaroni 1 , Maria Giulia Vincini 1 , Elena Rondi 3 , Federica Cattani 3 , Barbara Alicja Jereczek- Fossa 1,2 1 Division of Radiotherapy, European Institute of Oncology IRCCS, Milan, Italy. 2 Division of Radiotherapy, University of Milan, Milan, Italy. 3 Division of Medical Physics, European Institute of Oncology IRCCS, Milan, Italy Purpose/Objective: The aim of the present study is to evaluate the feasibility, safety, and early clinical outcomes of ultra- hypofractionated stereotactic body radiotherapy (UH- SBRT) delivered with CyberKnife® and a simultaneous integrated boost (SIB) to the dominant intraprostatic Poster Discussion 3093
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