S1235
Clinical - Urology
ESTRO 2026
Radiotherapy, N.N. Petrov Cancer Institute, St Petersburg, Russian Federation
patients (41.9%) were classified as low-risk and 255 (58.1%) as favourable intermediate-risk. Androgen deprivation therapy (ADT) was administered to 305 patients (69.6%), mainly due to historical institutional protocols and clinical discretion, primarily for prostate downsizing or symptom control before SBRT. Regarding acute toxicity, 245 patients (74%) experienced grade I–II GU toxicity, which was mild and self-limiting. Grade III GU toxicity occurred in only 3 patients (0.7%). More than 90% of patients (401) experienced no GI toxicity. Cumulative ≥ grade 2 late GU and GI toxicities were observed in 3% ( ≈ 13 patients) and 1.2% ( ≈ 5 patients), respectively, with no grade 4 events reported. The median follow-up was 112 months. Overall survival (OS) rates at 1, 3, and 5 years were 97.4%, 90.9%, and 83.1%, respectively. Ten- year PFS was 83%, and OS at 10 years was approximately 92%. At last follow-up, 402 patients were alive and 37 had died, 9 due to prostate cancer, resulting in a 10-year cancer-specific survival rate of approximately 97.9%. No statistically significant differences were observed between low- and favourable intermediate-risk groups in baseline characteristics or PSA evolution over time. Conclusion: SBRT delivering 35 Gy in 7 fractions for localized prostate cancer achieved excellent long-term tumour control and very low toxicity. The 10-year outcomes confirm the safety, efficacy of this ultrahypofractionated regimen, with consistent biochemical control across all risk subgroups References: - 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(10):1308-1320.- Romero Zoghbi SE et al. Acute toxicity of SBRT in localized prostate cancer: A Spanish multicenter study. Actas Urol Esp (Engl Ed). 2025;49(8):501798.- Lukka HR et al. Five-Year Patient- Reported Outcomes in NRG Oncology RTOG 0938, Evaluating Two Ultrahypofractionated Regimens for Prostate Cancer. Int J Radiat Oncol Biol Phys. 2023;116(4):770-778 Keywords: SBRT, prostate cancer, low-intermediate risk Digital Poster Highlight 2614 Long-Term Efficacy and Safety of Salvage Postoperative Stereotactic Body Radiotherapy for the Prostate Bed Sergey N Novikov, Nikita Kuznetcov, Roman Novikov, Nikolay Ilin, Ekaterina Samarceva, Uriy Merezhko, Julia Melnik, Sergey Kanaev
Purpose/Objective: To evaluate the long-term oncological outcomes and safety profile (with special attention to obstructive complications) of salvage stereotactic body radiation therapy (SBRT) following radical prostatectomy for prostate cancer Material/Methods: In 2019 we initiated single-center prospective observational study aiming at evaluating the efficacy and safety of postoperative SBRT for recurrent prostate cancer. From 2019 to 2023 56 patients with biochemical and clinical recurrences were included in the study and were available for analysis. SBRT was delivered as 5 fractions of 7Gy to the prostate bed (PB)
which was delineated according to the RTOG recommendations (1). In the cases of clinical
recurrences MRI and PSMA-PET-CT data was used for delineation of gross tumor volume. Planning target volume was created with 3 mm isotropic margins. The median follow-up after the end of SBRT was 42 months. Endpoints included biochemical recurrence- free survival, local control, quality of life and toxicity assessed by RTOG criteria. Biochemical failure after SBRT was defined as three consecutive increases in PSA measurements. Results: The biochemical recurrence-free survival rate was 76.8% at the last follow-up. Local recurrence occurred in 3 patients (5.4%), resulting in a local control rate of 94.6%. Regional recurrences in pelvic lymph nodes were diagnosed in 4 patients (7.1%), distant metastases – in 1 (1.8%), only biochemical failure – in another 5 (8.9%) cases.Acute grade 1 genitourinary (GU) toxicity was observed in 19.6% of patients. Acute grade 1 and 2 gastrointestinal (GI) toxicity was detected in 4 (7.1%) and 4 (7.1%) cases. The incidences of late grade 1 or 2 GU toxicity were 22 (39.3%) and 3 (5.4%); late grade 1 or 2 gastrointestinal toxicity (GI) – were 4 (7.1%) and 1 (1.8%). No grade ≥ 3 toxicities were reported. There were no cases of severe obstructive symptoms that require invasive procedures. Quality of life scores remained stable throughout the study.
Fig. 1 Biochemical disease free survival after salvage
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