S1223
Clinical - Urology
ESTRO 2026
3 German Oncology Center, European University Cyprus, Limassol, Cyprus. 4 Department of Radiation Oncology, Medical Center - University of Freiburg, Freiburg, Germany. 5 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany. 6 Division of Radiation Oncology, European Institute of Oncology, IRCCS, Milan, Italy. 7 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy Purpose/Objective: The Consortium for Implementation of PSMA-PET in Prostate Cancer Radiotherapy Trials (Co-IMPACT) was established to address the gap between rapid clinical adoption of prostate-specific membrane antigen positron emission tomography (PSMA-PET) and evidence-based guidelines. This survey aimed to characterize current practices in PSMA-PET guided radiotherapy (RT) across participating centers and assess willingness to contribute data to four distinct clinical cohorts. Material/Methods: An international survey was conducted among 43 academic and private radiation oncology centers from 16 countries across four continents with expertise in PSMA-PET guided RT. The survey comprised 362 questions covering technical infrastructure, PSMA-PET utilization, treatment approaches for primary prostate cancer, postoperative RT, radiorecurrent disease, and oligoprogressive castration-resistant prostate cancer (CRPC). Data were analyzed descriptively using median and interquartile range (IQR) for continuous variables and frequencies for categorical variables. Results: High participation rates were observed across all cohorts: Co-IMPACT 1 (primary prostate cancer) 88% (38/43), Co-IMPACT 2 (postoperative RT) 88% (38/43), Co-IMPACT 3 (radiorecurrent disease) 86% (37/43), and Co-IMPACT 4 (oligoprogressive CRPC) 77% (33/43). Centers reported a median of 300 (IQR: 180-500) PSMA-PET scans annually for prostate cancer patients, with 90% (IQR: 73-100%) performed in-house. All centers had conventional linear accelerators, while 56% had dedicated SBRT systems (i.e. helical linacs, robotic RT systems, MR-linacs), and 21% proton therapy facilities.A median of 140 (IQR: 50-305) primary prostate cancer cases were treated, moderate hypofractionation (MHF) was the predominant
fractions per week). The biologically effective dose (BED) corresponded to 202.7 Gy for prostate tissue ( α / β = 1.5 Gy) and 117 Gy for organs at risk ( α / β = 3 Gy).All treatments were delivered without a urinary catheter or rectal balloon. Genitourinary (GU) and gastrointestinal (GI) toxicities were recorded at each follow-up according to CTCAE v4/EORTC-RTOG criteria. Prostate-specific antigen (PSA) levels were measured between 3 and 6 months after treatment and every 6 months thereafter. Results: Between 2019 and 2025, 57 patients were treated (median age 71 years, range 53–83). Most had Gleason 3+3 tumors (84.2%) and clinical stage T1c (75.4%) or T2a (17.5%); ECOG 0 was recorded in 89.5%. Mean prostate volume was 39.4 cc, and 15.8% received short-term androgen deprivation therapy.SBRT was well tolerated, with only mild and transient acute toxicity. Grade 1 GU, GI, and skin events occurred in 18.2%, 7.7%, and 8.8% of patients, respectively; grade 2 GU toxicity was observed in 3.6%, and no grade ≥ 3 events occurred. One patient required temporary urinary catheterization, recovering normal voiding within days without sequelae.PSA showed a progressive and sustained decline, from 5.95 ng/mL at baseline to 1.48 ng/mL at 3 months (56/57 patients), 0.88 ng/mL at 6 months (40/57), 0.57 ng/mL at 12 months (36/57), 0.35 ng/mL at 18 months (26/57), and 0.22 ng/mL at 24 months (19/57) (p < 0.001). The median International Prostate Symptom Score (IPSS) improved from 3.5 pre-treatment to 1 post-treatment (p < 0.001), reflecting excellent urinary tolerance. Conclusion: This updated analysis with extended follow-up demonstrates that SBRT 32 Gy in four fractions for localized prostate cancer is safe, well tolerated, and associated with minimal GU/GI toxicity and durable biochemical control. Treatment without a urinary catheter or rectal balloon was feasible, with only transient catheterizations, supporting this regimen as effective and minimally invasive. Keywords: Prostate, SBRT Current practices in PSMA-PET guided radiotherapy for prostate cancer: Results from the Co-IMPACT consortium international survey Tobias Hölscher 1,2 , Constantinos Zamboglou 3,4 , Andreas Christoforou 3 , Nina Schmidt-Hegemann 5 , Giulia Marvaso 6,7 , Nasr Salman 1 1 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany. 2 National Center for Tumor Diseases (NCT), NCT/UCC Dresden, Dresden, Germany. Poster Discussion 2311
fractionation schedule (92%), followed by SBRT/ultrahypofractionation (38%) and HDR
brachytherapy (33%). Regarding elective pelvic nodal irradiation in PSMA-PET node-negative (cN0) patients, 2 centers never use elective pelvic RT, while 22 centers (59%) treat high-risk (NCCN) and 28 centers (76%) very high-risk (NCCN) patients electively. However, 26 centers individualize their decision-making based on additional factors including individualized patient
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