S176
Brachytherapy - Urology
ESTRO 2026
Material/Methods: Consecutive patients with(1) biopsy- proven PCa, (2) N0M0 stage, (3) prostate volume ≤ 100cm ³ , (4) baseline International Prostate Symptom Score (IPSS) ≤ 20, and (5) treated with definitive HDR or SBRT in monotherapy between 2010 and 2023 from our single institution were included. Exclusion criteria included prior treatment and concurrent non- melanoma skin malignancies.Propensity score matching was performed using 1:3 HDR- BT:SBRTmaximumratio and a caliper of 0.1. Matching variables included ADT use, age, pre-treatment PSA, T stage, ISUP grade group, and NCCN risk category.Demographic, clinical, and treatment data were collected for all included patients. Biochemical recurrence was defined using Phoenix criteria. Study endpoints included biochemical recurrence-free survival (BRFS), clinical progression-free survival (CPFS), distant metastasis-free survival (DMFS), and overall survival (OS). Kaplan–Meier curves with log- rank tests to compare groups and multivariable Cox models were used to assess outcomes. Results: A total of 685 patients (175 HDR-BT and 510 SBRT) were included for analysis, with well- balanced matchingvariables (mean differences <0.10), and a median follow-up of 37 months (IQR 19-56).The matched cohort baseline and treatment characteristics are summarized in Table 1. Median timewas not reached for any survival outcome. Five - year actuarial rates for HDR - BT versus SBRT were as follows: BRFS 95.7% (95% CI: 92.7-98.7%) versus 88.5% (95% CI: 82.4-95%) (p=0.46); CPFS 96.6% (95% CI: 94.7- 98.5%) versus 88.9% (95% CI: 84.1-94.0%) (p=0.35); DMFS 98.0% (95% CI: 96.7- 99.4%) versus 93.5% (95% CI: 89.4-97.7%) (p=0.84); and OS 98% (95% CI: 96.7-99.4%) versus 95.4% (95% CI: 92.2-98.7%) (p=0.46). Competing risk sensitivity analyses confirmed these results.
Conclusion: Our results confirm that HDR - BT and SBRT are effective treatments for localized PCa, providing similar cancer control in matched patients, aligning with previously reported evidence.1,2 These results further support that treatment selection should be based on other patient and institution-specific characteristics, including patient preference, performance status, baseline urinary symptoms, prostate anatomy, and institutional expertise. Keywords: SBRT, HDR brachytherapy, propensity score matching References: 1.Levin-Epstein R, Cook RR, Wong JK, et al. Prostate- specific antigen kinetics and biochemical control following stereotactic body radiation therapy, high dose rate brachytherapy, and low dose rate brachytherapy: A multi-institutional analysis of 3502 patients. Radiother Oncol J Eur Soc Ther Radiol Oncol. 2020;151:26-32. doi:10.1016/j.radonc.2020.07.014 2.Correa RJM, Morton G, Chung HT, et al. Two-fraction stereotactic ablative radiotherapy (SABR) versus two-fraction high
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