S164
Brachytherapy - Urology
ESTRO 2026
patients; 26% had Gleason score ≥ 8, and 29.4% had clinical stage ≥ cT3. Most patients received long-term ADT (24–36 months). Freedom from biochemical failure (FFBF) was 88.5% at 5 years and 76% at 10 years in both cohorts, with no significant difference between CT-based and TRUS-based planning. For the CT-based group, metastasis-free survival (MFS) and overall survival (OS) were 94.7% and 95% at 5 years, and 90.2% and 82% at 10 years, respectively. In the TRUS-based group, MFS and OS were 92.6% and 88.1% at 5 years, and 86.3% and 67.2% at 10 years, respectively. Differences between groups did not reach statistical significance. However, the cumulative incidence of grade ≥ 3 genitourinary (GU) adverse events was significantly higher in the CT-based group (11.2% and 13.5% at 5 and 10 years) compared with the TRUS-based group (2% and 3.3%, respectively) (P <0.01). Gastrointestinal (GI) grade ≥ 3 adverse events remained low in both groups, with no clinically relevant differences over time.
A, Dhar A, Fakir H, Mendez LC, Warner A, et al. PSMA MRI Guided prOstate SBRT (ARGOS)/Comprehensive, Longitudinal Evaluation of IMaging BiomarkErs Post Radiotherapy (CLIMBER) Phase I/II Trial. Int J Radiat Oncol Biol Phys. 2025 Oct 1;123(2):395-405. PMID: 40349854. Poster Discussion 1670 CT-based versus TRUS-based High-Dose-Rate brachytherapy boost in prostate cancer: long-term oncological outcomes Alai Goñi 1 , David Büchser 2,3 , Mikel Eguiguren 1 , Eva Sáenz de Urturi 1 , Usoa Iceta 1 , Itziar Valverde 4 , José Fernando Perez 4 , Vicent Pastor 5 , Albert Bartrés 5 , Carlos Mascarell 2 , Ana Hompanera 2 , Lide del Castillo 2 , Daniel Roura 1 , Beraldo Martinez 1 , Ane Mugica 1 , Amaia Sanchez 1 , Maider Campo 1 , Leyre Gonzalez 1 , Intza Uranga 1 , María Pagola 1 , Julián Minguez 1 , Jose María Urraca 1 , Jon Cacicedo 2,3 , Arrate Querejeta 1 , Alfonso Gómez-Iturriaga 2,3 1 Radiation Oncology, Onkologikoa - Hospital Universitario Donostia, San Sebastian, Spain. 2 Radiation Oncology, Hospital Universitario Cruces, Barakaldo, Spain. 3 Radiology and Physical Medicine, Instituto de Investigación Sanitaria Biobizkaia, Barakaldo, Spain. 4 Medical Physics, Hospital Universitario Cruces, Barakaldo, Spain. 5 Medical Physics, Onkologikoa - Hospital Universitario Donostia, San Sebastian, Spain Purpose/Objective: To determine and compare long-term biochemical control, survival outcomes, and adverse event profiles between two high-dose-rate (HDR) brachytherapy boost techniques (CT-based two-step versus TRUS- based single-step) in patients with localized prostate cancer. Material/Methods: Between October 2004 and December 2018, a total of 730 patients with localized prostate cancer underwent HDR brachytherapy boost (378 with CT-based and 352 with TRUS-based techniques) across two institutions. Datasets were harmonized, and key covariates (PSA, prostate volume, clinical stage, ISUP grade, and ADT duration) were standardized. Propensity scores were generated for 1:1 caliper matching, yielding 102 well- balanced pairs (n = 204). Additionally, an inverse probability of treatment weighting (IPTW) analysis with Stürmer trimming was performed as a complementary causal inference approach. Results: The final matched cohort included 204 patients with a median follow-up of 122.9 months. Median age at brachytherapy was 70.5 years, and median PSA was 14 ng/mL. High-risk disease was present in 64.4% of
Conclusion: To our knowledge, this is the first real-world study directly comparing long-term outcomes of HDR brachytherapy boost techniques in prostate cancer. Both CT-based and TRUS-based approaches achieved excellent biochemical control and survival outcomes; however, CT-guided brachytherapy was associated with a significantly higher cumulative incidence of late grade ≥ 3 GU adverse events. Keywords: Prostate, HDR, Boost
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