ESTRO 2025 - Abstract Book

S2002

Clinical - Urology

ESTRO 2025

13 Radiation oncology, Clinique des Dentellières, Valenciennes, France. 14 Radiation oncology, Centre azuréen de cancérologie, Mougins, France. 15 Radiation oncology, Institut de cancérologie de Bourgogne, Dijon, France. 16 Radiation oncology, CHU Lyon Sud, Lyon, France. 17 Radiation oncology, Institut Sainte Catherine, Avignon, France. 18 Radiation oncology, CHU Tours, Tours, France. 19 Radiation oncology, Clinique mutualiste, Saint-Nazaire, France. 20 Statistics, Institut de cancérologie de l'Ouest, Nantes, France Purpose/Objective: Stereotactic Body Radiotherapy (SBRT) is effective in controlling local disease in oligorecurrent prostate cancer (PCa), and a combination of checkpoint inhibitors (CPI) and SBRT may have synergistic effects. We aimed to determine whether durvalumab, a PD-L1 CPI combined with SBRT improves progression-free survival in patients with castration-sensitive oligorecurrent PCa. Material/Methods: POSTCARD is a multicenter, open-label, randomized phase II trial in 8 centers. Eligible patients were castration sensitive oligorecurrent PCa up to 5 metastases (lymph node and/or bone). Patients were randomly assigned in a 2:1 ratio to arm A (12 injections of durvalumab 1500 mg every four weeks with SBRT to all metastases [27-33 Gy in 3 or 5 fractions] after one month of durvalumab), and arm B (SBRT alone). The primary endpoint was two-year progression-free survival (PFS). The secondary endpoints included PSA response, androgen deprivation therapy (ADT)-free survival and toxicity. Circulating immune cell populations and PD-L1 expression in circulating tumor cells (CTCs) were quantified in arm A at three time points: TP1 prior to any treatment; TP2 after one month of CPI and TP3 after 3 months of CPI. Results: Between March 2019 and December 2021, 109 patients were screened, of which 96 were randomly assigned to receive either durvalumab plus SBRT (n=63) or SBRT alone (n=33). At 2 years, PFS was of 23% (95% CI 14-36%) in arm A and of 26% (95% CI 14-48%) in arm B, and ADT-free survival was 56% in arm A and 47% in arm B. A very good PSA response (PSA nadir <0.2 ng/ml) was noted in 11 patients in arm A and 3 patients in arm B. A very good PSA response persisted at 2 years in 7 patients in arm A and 1 patient in arm B. Grade 3+ immune-related toxicity occurred in 5 patients (8%) in arm A, and no grade 3+ radiotherapy-induced toxicity was observed. At TP1, CTCs were detected in 22 patients (23 assessed) and 78.3% of these patients showed at least one PDL1 + CTC. Kaplan Meyer analysis showed a significantly better PFS in patients with less that 5 CTCs/10 mL of blood detectable at TP1 (p<0.05). Further immune analyses are ongoing. Conclusion: Compared to SBRT alone, the combination of SBRT with durvalumab did not improve progression-free survival at 2 years in patients with castration-sensitive oligorecurrent PCa. Some selected patients may benefit from the addition of durvalumab to SBRT. CTC number may help discriminating responding and non-responding patients.

Keywords: SABR, oligometastases, immunotherapy

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Digital Poster Engaging prostate cancer patients in patient-reported outcome measures through MyChart: participation trends and challenges during radiotherapy Thomas Götzfried, Mariangela Caimi Radiation Oncology, Cantonal Hospital of Lucerne, Lucerne, Switzerland

Purpose/Objective: