S1309
Clinical - Urology
ESTRO 2026
Conclusion: Adaptive whole-bladder and bladder tumour-focused radiotherapy achieves significantly lower incidental dose to regional pelvic lymph nodes as compared to historical 3DCRT. The clinical significance of this reduction warrants further investigation. References: 1. Alfred Witjes, J., et al., European Association of Urology Guidelines on Muscle-invasive and Metastatic Bladder Cancer: Summary of the 2023 Guidelines. Eur Urol, 2024. 85(1): p. 17-31.2. Goldsmith, B., et al., Occult pelvic lymph node involvement in bladder cancer: implications for definitive radiation. Int J Radiat Oncol Biol Phys, 2014. 88(3): p. 603-10.3. James, N.D., et al., Radiotherapy with or without chemotherapy in muscle-invasive bladder cancer. N Engl J Med, 2012. 366(16): p. 1477-88.4. Hafeez, S., et al., Bladder Tumor-Focused Adaptive Radiation Therapy: Clinical Outcomes of a Phase I Dose Escalation Study. Int J Radiat Oncol Biol Phys, 2025. 121(1): p. 165-175. Keywords: Adaptive radiotherapy, nodal irradiation, bladder Mini-Oral 4879 One-year cumulative toxicity in 25 prostate cancer patients treated with single fraction (24 Gy) urethra-sparing radiosurgery (PRO-FAST- NCT05936736 ) Andrei Fodor 1 , Laura Giannini 1 , Miriam Torrisi 1 , Sara Broggi 2 , Andrea Losa 3 , Tommaso Maga 3 , Roberta Tummineri 1 , Alessia Tudda 2 , Chiara L Deantoni 1 , Carmen Gigliotti 2 , Gaia Parma 1 , Roberta Castriconi 2 , Paolo Passoni 1 , Paola Mangili 2 , Antonella Del Vecchio 2 , Claudio Fiorini 2 , Nadia G Di Muzio 1,4 1 Radiation Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 2 Medical Physics, IRCCS San Raffaele Scientific Institute, Milan, Italy. 3 Urology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 4 Medicine and Surgery, Vita-Salute San Raffaele University, Milan, Italy Purpose/Objective: To report the one-year cumulative toxicity outcomes of the first 25 prostate cancer patients treated with robotic radiosurgery delivering a total dose of 24 Gy in a single fraction to the prostate and seminal vesicles in the PRO-FAST trial (NCT05936736). Material/Methods: The PRO-FAST trial, evaluating single-session radiosurgery (24 Gy) for prostate cancer, received institutional ethics approval and was designed according to Simon’s optimal two-stage model. Seventy patients are planned in total; 13 were enrolled in phase I, with continuation dependent on the occurrence of ≤ 1 grade ≥ 3 toxicity within one-month
V40 of the CTVn and nodal subgroups, were extracted. Results:
Fifty plans were recreated and analysed. Across all planning strategies, incidental nodal doses were low (Table 1). The obturator CTV consistently received the highest dose. The obturator CTV V40 was 53%, 48%, 29%, 21%, and 22% for the 3DCRT, large, medium, small, and SIB plans, respectively. The V40 of all other nodal subgroups was less than 30% across all techniques. CTVn Dmean varied significantly between the groups (p< 0.001), following the order of 3DCRT > large > medium > small ≈ SIB (Figure 1). Differences between small and SIB plans were minimal.Table 1. Dmean and V40 nodal CTV according to radiotherapy planning technique
Figure 1. Comparison of Dmean to composite nodal group (CTVn) according to planning technique
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