S1300
Clinical - Urology
ESTRO 2026
Material/Methods: 102 patients were randomized 1:1 to Arm A (SBRT) or Arm B (SBRT + ADT). Median follow-up (Reverse KM) was 49.23 months (95% CI 42.47–54.8). CPFS was defined as time from randomization to biochemical or clinical progression.Eugonadal CPFS was calculated in both arms, starting from testosterone recovery to recurrence or last follow-up; patients without recovery or with progression before recovery were excluded. CRFS was defined as time to castration-resistant disease. Kaplan–Meier survival curves were compared using log-rank and Cox models. Results:
Results: 103 UIR patients received a DIL-SIB with 9, 8 and 86 patients treated at 26.4Gy, 28.8Gy and 30Gy, respectively. Median CTV was 57.5 cm3. Median DIL volume was 5.4 cm3, encompassing a median 9.4%of the CTV. Acute grade ≤ 2 GU and GI toxicities were 55.3% and 17.5%, respectively. There were no cases of grade ≥ 3 acute toxicities. At a median follow-up of 38.2 months, late G2 GU and GI toxicities were 8.7% and 1%, respectively. No grade ≥ 3 late GI or GU toxicities were observed. The 36-month median PSA was 0.42 ng/ for the entire cohort. A Phoenix definition failure was observed in 5 patients (4.8%). 68Ga-PSMA scanning at the time of relapse confirmed 2 DIL relapses and 3 distant-only progressions. Conclusion: These preliminary trial outcomes provide evidence that a 68Ga-PSMA-PET-guided 30Gy SIB-DIL in addition to a whole gland 24Gy SDRT can be administered safely with encouraging clinical outcomes. Keywords: SBRT, single-fraction, dose painting Proffered Paper 4586 Updated clinical outcomes from the RADIOSA randomized phase II trial Giulia Marvaso 1,2 , Maria Giulia Vincini 1 , Chiara Lorubbio 1 , Cristiana Fodor 1 , Stefano Luzzago 3 , Alessandro Francesco Mistretta 3,2 , Giuseppe Petralia 4,2 , Nicola Fusco 5,2 , Gabriella Pravettoni 6,2 , Gennaro Musi 3,2 , Chad Tang 7 , Phuoc Tran 7 , Piet Ost 8 , Barbara Alicja Jereczek-Fossa 1,2 1 Division of Radiation Oncology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 2 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy. 3 Division of Urology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 4 Division of Radiology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 5 Division of Pathology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 6 Division of Applied Research for Cognitive and Psychological Sciences, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 7 Department of Genitourinary Radiation Oncology, MD Anderson Cancer Center, Milan, Italy. 8 Department of Radiation Oncology,, Iridium Network, Wilrijk, Belgium Purpose/Objective: The phase II RADIOSA trial compared stereotactic body radiotherapy (SBRT) alone (Arm A) versus SBRT + 6- month androgen deprivation therapy (ADT, Arm B) in oligorecurrent hormone-sensitive prostate cancer (PCa). The initial results showed improved clinical progression-free survival (CPFS) with the combination. We report the updated long-term outcomes including CPFS, eugonadal CPFS (after testosterone recovery), and castration-resistant-free survival (CRFS).
Clinical progression occurred in 41/51 (80.4%) Arm A and 31/51 (60.8%) Arm B patients.Median CPFS (Figure 1) was 15.13 months (95% CI 11.23–22.1) in Arm A vs 32.67 months (95% CI 24.63–NA) in Arm B (log rank test, p = 0.00088; Cox model HR =0.4604, 95% CI 0.288–0.736, p = 0.001).All patients enrolled in arm B, except two, achieved testosterone recovery within the follow-up period. After testosterone recovery, eugonadal CPFS curves (Figure 2) remained numerically separated but without statistical significance, suggesting partial convergence between the two arms once normal testosterone levels were restored.Castration-resistant progression occurred in 17 patients overall (11 Arm A, 6 Arm B)suggesting a delay in systemic evolution in the combined arm. Two- year OS remained high (95%, CI 90.9–99.4) with no between-arm difference. Conclusion:
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