ESTRO 2025 - Abstract Book

S385

Brachytherapy - Urology

ESTRO 2025

3. Marisa A. Kollmeier et al. Salvage brachytherapy for recurrent prostate cancer after definitive radiation therapy: A comparison of low-dose-rate and high-dose-rate brachytherapy and the importance of prostate-specific antigen doubling time. Brachytherapy 16 (2017) 1091e1098.

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Digital Poster HDR brachytherapy as monotherapy in the treatment of high-risk prostate cancer Oxana Komina, Bettina Kohl, Ayurzana Purevdorj, Thomas Pajer, Elisabeth Nechvile Institute of Radiooncology, Klinik Hietzing, Vienna, Austria

Purpose/Objective: Radiotherapy (RT) plays a critical role in the treatment of high-risk prostate cancer. Recently there are many efforts to perform dose escalation using advanced radiation technology. The high dose rate brachytherapy (HDR-BT) as monotherapy allows for an extreme dose escalation and a very good sparing of organs at risk (OAR). HDR-BT as a boost in addition to external beam radiation therapy (EBRT) shows better local control in the treatment of high and very high-risk prostate cancer and should be used in this cohort of patients. Although it is not a standard procedure, some high- and very high-risk patients in our center received HDR-BT as monotherapy due to health issues or individual preferences excluding them from receiving EBRT. Material/Methods: We summarized the data of those patients treated in our institution since implementation of the real-time planning system based on 3D ultrasound imaging in 2010. In total, according to the actual NCCN criteria, we treated 20 high or very high-risk patients with HDR-BT as monotherapy with calculated EQD2 108 Gy, BED 252 Gy (assuming α/β ratio of 1.5) between 01/2010 and 12/2023. Gastrointestinal (GI) and urogenital (GU) acute and late toxicities were documented according to RTOG/EORTC criteria. Biochemical control was recorded according to Phoenix definition. Results: The average age was 66 years (56-81). The median PSA was 9,8 ng/ml (3,2-122,0). The median follow-up length was 51 month (7-120). 3 patients received ADT; medium duration of therapy was 40,7 months. The overall survival (OS) was 95,0%, 3 patients had local recurrence only, 14 patients were free from any recurrence during the follow-up period. Patients had a very favorable profile of acute and late GI and GU toxicities, i.e. 0% severe (G≥3) acute or late GU toxicities and no (0%) severe (G≥3) acute or late GI toxicities. Conclusion: The effectiveness of HDR- BT as monotherapy in low- and intermediate risk prostate cancer as well as a very favorable profile of acute and late toxicities has already been demonstrated and published (1, 2). As expected, our results show an extremely favorable profile of the treatment-associated toxicities. Yet the small number of patients and a big heterogeneity due to the development of pre-treatment diagnostics since 2010 are making comparison and evaluation of the data difficult. Further multicenter studies should be initiated to evaluate the possibilities of HDR-BT.

Keywords: Dose escalation, toxicity

References: 1. Tsang YM, Tharmalingam H, Belessiotis-Richards K, Armstrong S, Ostler P, Hughes R, Alonzi R, Hoskin PJ. Ultra hypofractionated radiotherapy for low- and intermediate risk prostate cancer: High-dose-rate brachytherapy vs stereotactic ablative radiotherapy. Radiother Oncol. 2021 May;158:184-190. 2. Moll M, Nechvile E, Kirisits C, Komina O, Pajer T, Kohl B, Miszczyk M, Widder J, Knocke-Abulesz TH, Goldner G. Radiotherapy in localized prostate cancer: a