ESTRO 2025 - Abstract Book

S1922

Clinical - Urology

ESTRO 2025

1033

Mini-Oral Stereotactic body radiotherapy vs HDR brachytherapy for prostate cancer: the SHERBET individual patient data meta-analysis of five prospective trials Cristian Udovicich 1,2 , Patrick Cheung 1,2 , William Chu 1,2 , Hans Chung 1,2 , Jay Detsky 1,2 , Stanley Liu 1,2 , Gerard Morton 1,2 , Ewa Szumacher 1,2 , Chia-Lin Tseng 1,2 , Danny Vesprini 1,2 , John M Hudson 1,2 , Wee Loon Ong 1,2,3 , Thomas Kennedy 1,2 , Joelle Helou 1,2 , Melanie Davidson 1,2 , Ananth Ravi 2 , Merrylee McGuffin 1,2 , Liying Zhang 1 , Alexandre Mamedov 1 , Andrea Deabreu 1 , Meghan Kulasingham-Poon 1 , Andrew Loblaw 1,2,4 1 Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada. 2 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 3 Alfred Health Radiation Oncology, School of Translational Medicine, Monash University, Melbourne, Australia. 4 Department of Health Policy, Measurement and Evaluation, University of Toronto, Toronto, Canada Purpose/Objective: Stereotactic body radiotherapy (SBRT) and high-dose-rate brachytherapy monotherapy (HDR-BT) are potential options for intermediate-risk prostate cancer. There has been no prospective data comparing these two techniques. We pooled individual patient data from prospective trials to assess efficacy and toxicity. Material/Methods: This was an individual patient data meta-analysis of five prospective trials. Eligibility criteria included men with intermediate-risk prostate cancer undergoing five-fraction SBRT, two-fraction SBRT with GU-Lok or two-fraction HDR-BT. Patients receiving ADT were excluded. The primary endpoint was biochemical failure (BCF) comparing SBRT and HDR-BT. Secondary endpoints included toxicity outcomes. Clinician-reported GU and GI adverse events (AEs) were recorded using CTCAE; and were available for the acute and late period. Patient-reported quality of life (PRQoL) data was available for the late period. Results: Overall, 247 men met the eligibility criteria; 180 men (73%) underwent SBRT and 67 men (27%) underwent HDR-BT. Significantly more men in the SBRT cohort had unfavourable intermediate-risk disease (62% vs. 39% for HDR-BT, p<0.01). The median follow-up was 9.5 years (IQR 5.5-10.6). The cumulative incidence of BCF was significantly higher in the HDR-BT cohort (p<0.01). At five years, the BCF for HDR-BT was 7.8% (95% CI 1.0-14.6%) and was SBRT was 3.0% (95% CI 0.4-5.6%). At ten years, BCF was 38.0% (95% CI 19.8-56.1%) for HDR compared to 10.4% (95% CI 4.3-16.6%) for SBRT. The increased BCF for HDR-BT was significant for men with favourable (p<0.01) and unfavourable (p=0.02) intermediate-risk disease. After multivariable analysis for BCF, significant covariates included HDR-BT (HR 4.2, 95% CI 2.0-8.7, p<0.01) and baseline PSA (HR 3.3, 95% CI 1.5-7.1, p<0.01). HDR- BT had an increased incidence of acute Grade ≥2 GU AEs (p<0.01) and no significant difference in acute Grade ≥2 GI AEs or late Grade ≥2 GU or GI AEs. For the late period, there was no significant difference in PRQoL. Conclusion: This is the first prospective comparison of SBRT and HDR-BT. Further strengths include the extended follow-up and utilization of individual patient data. In our meta-analysis, SBRT has excellent long-term efficacy with significantly decreased BCF compared to HDR-BT. We encourage that two-fraction HDR-BT without ADT should only be given on trial for men with intermediate-risk prostate cancer.

Keywords: SBRT, SABR, brachytherapy, prostate