S1137
Clinical - Urology
ESTRO 2026
Australia. 3 Department of Medicine, University of Notre Dame, Fremantle, Australia. 4 Department of Palliative Care, Fiona Stanley Hospital, Murdoch, Australia. 5 Murdoch Oncology Centre (SJOG Murdoch), Genesiscare, Murdoch, Australia. 6 Clinical Research, GenesisCare, Murdoch, Australia. 7 Wexford Medical centre, SJOG Murdoch, Muroch, Australia Purpose/Objective: Salvage pelvic nodal radiotherapy (SPRT) combined with androgen deprivation therapy (ADT) is an established treatment for men with prostate-specific membrane antigen (PSMA)-expressing recurrent pelvic nodal prostate cancer (PC)1. However, ADT is associated with significant adverse effects and increased cost2. PSMA radioligand therapy (RLT) has shown safety and efficacy in castration-resistant metastatic PC. 3-4. This study aimed to evaluate the safety and efficacy of combining SPRT with RLT, without ADT, in men with PSMA-expressing oligorecurrent pelvic nodal metastases (POPLNM). Material/Methods: We conducted a single-arm, open-label, phase 2 trial at GenesisCare Murdoch (Perth, Australia). Eligible patients had biopsy-proven Gleason ≥ 7 prostate adenocarcinoma, biochemical recurrence after definitive local therapy, and PSMA-PET–confirmed POPLNM ( ≤ 5 nodes, below the aortic bifurcation). Radiotherapy included elective pelvic nodal RT to 54 Gy and PSMA-avid involved nodes to 66 Gy in 30 fractions using VMAT technique. RLT was administered 4 weeks post-SPRT as two infusions of ¹⁷⁷ Lu-TLX591- CHO (2.81 GBq lutetium-177 radiolabelled DOTA- rosopatamab; 20 mg total antibody mass), 14 days apart. The primary endpoint was PSA progression-free survival (PSA-PFS); secondary endpoints included radiographic PFS, time to ADT initiation, and treatment related toxicities. Results: Between November 2022 and October 2023, five patients were enrolled (median age 65 years, IQR 58– 74; median Gleason 7, IQR 7–8). Baseline median PSA, number of POPLNM, and SUVmax were 0.73 ng/mL (IQR 0.27–9.5), 1 (IQR 1–2), and 4.5 (IQR 1.8–26.8), respectively. Median PSA decreased to 0.36 ng/mL post-SPRT but before RLT. All patients completed both treatments within the protocol timeframe. After a median follow-up of 21 months (IQR 19–27), 80% achieved >50% and >95% PSA declines (median PSA 0.025 ng/mL, IQR <0.01–0.079); 80% demonstrated complete metabolic response on 6-month PSMA PET; and 80% remained ADT-free. One patient developed PSA progression with PSMA-avid metastases at 12 months and commenced ADT.Grade ≥ 3 hematologic adverse events occurred in 60% (3/5): grade 4 thrombocytopenia (3/5), grade 4 neutropenia (2/5), and grade 3 anaemia (1/5). All were asymptomatic;
only one patient required G-CSF and platelet transfusion. Counts normalized within 1-3 months. No ≥ grade 3 SPRT genitourinary or gastrointestinal toxicities, late toxicities, or treatment-related deaths were observed. Conclusion: Combining SPRT with ¹⁷⁷ Lu-TLX591-CHO RLT, without ADT, achieved promising biochemical and metabolic responses while delaying the need for ADT in PSMA- positive oligorecurrent pelvic nodal PC. These findings support further evaluation in randomized trials to confirm efficacy and refine safety profiles References: 1. Ost P, et al. Salvage metastasis-directed therapy versus elective nodal radiotherapy for oligorecurrent nodal prostate cancer metastases (PEACE V–STORM): a phase 2, open-label, randomised controlled trial. Lancet Oncol. 2025;26(6):695–706.2. Nguyen PL, et al. Adverse effects of androgen deprivation therapy and strategies to mitigate them. Eur Urol. 2015;67(5):825– 36.3. Sartor O, et al. Lutetium-177–PSMA-617 for metastatic castration-resistant prostate cancer. N Engl J Med. 2021;385(12):1091–103.4. Hofman MS, et al. Overall survival with [177Lu]Lu-PSMA-617 versus cabazitaxel in metastatic castration-resistant prostate cancer (TheraP): secondary outcomes of a randomised, open-label, phase 2 trial. Lancet Oncol. 2024;25(1):99–107. Keywords: Prostate, Oligorecurrent, PSMA Stereotactic Body Radiotherapy for Localized Prostate Cancer: Two-Year Tolerability and Biochemical Control in a Multicenter Spanish Cohort. Sigfredo E Romero Zoghbi 1,2 , Fernando López Campos 3,4 , Cristina Laria 1 , Abrahams Ocanto 4 , David Sanz-Rosa 5 , Israel Thuissard - Vasallo 5 , Cristina Andreu - Vázquez 6 , Jaume Fernández - Ibiza 7 , Jon Andreescu Yagüe 8 , Evita Krumina 9 , Maria Mateos 10 , Luis Alberto Glaría 4 , Daniela Gonsalves 4 , Castalia Fernández 4 , David Esteban 11 , José Begara de la Fuente 12 , Daniel Rivas 12 , Escarlata López 12 , José Antonio González Ferreira 13 , Antonio Ristori 14 , Ana Belén Bezares Alarcón 15 , Loubna Aakki 16 , Luis Larrea 17 , Jose Angel García Cuesta 18 , Felipe Couñago 4,5 1 Department of Radiation Oncology, GenesisCare Talavera de la Reina, Talavera de la Reina, Spain. 2 Doctoral and Research School, Universidad Europea de Madrid, Madrid, Spain. 3 Department of Radiation Oncology, Hospital Universitario Ramón y Cajal, Madrid, Spain. 4 Department of Radiation Oncology, GenesisCare Madrid, Hospital Universitario La Milagrosa, Madrid, Spain. 5 Department of Medicine, Faculty of Medicine, Health and Sports, Universidad Digital Poster Highlight 396
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