S1166
Clinical - Urology
ESTRO 2026
Chicoutimi, Canada. 7 Radiation Oncology, Jewish General Hospital, Montréal, Canada. 8 Radiooncologie, Centre intégré de santé et de services sociaux de l'Outaouais, Gatineau, Canada. 9 Radiooncologie, Centre hospitalier régional de Trois-Rivières, Trois- Rivières, Canada. 10 Radiooncologie, Centre de santé et de services sociaux de Rimouski-Neigette, Rimouski, Canada. 11 Radiation Oncology, McGill University Health Centre, Montréal, Canada. 12 Radiation Oncology, Nova Scotia Cancer Centre, Halifax, Canada Purpose/Objective: To compare differences in clinical outcomes between intermediate (IRPCa) and high risk (HRPCa) prostate cancer using NCCN classification in two simultaneous phase III trials. Material/Methods: From October 2000 to September 2010, 1230 patients (pts) with localised prostate cancer were randomised, in 11 cancer centers in Canada, into two phase III trials: 600 pts with IRPCa and 630 with HRPCa. IRPCa and HRPCa pts were defined using the NCCN classification and treated with radiotherapy (RT) and ± androgen depletion therapy (ADT).Inclusion criteria were histologically proven adenocarcinoma, Zubrod performance scale 0-1, age ≤ 80 years, and no evidence of regional or metastatic disease. Biochemical failure (BF), distant metastases (DM) and prostate cancer- specific mortality (PCSM) were analyzed with competing risks methods. Overall survival (OS) and distant metastases-free survival (DMFS) rates were analyzed with the Kaplan Meier method and the log- rank test. We examined the impact of the NCCN classification on outcomes. Results: Results are reported with a median follow-up of 17.4 years (IQR 13.2-20.6). Among the 1230 subjects analyzed, there were no differences in patient characteristics, i.e., age, Zubrod and comorbidities. The two groups differ only by NCCN classification. All outcomes were significantly worse in HRPCa compared to IRPCa patients: BF 31.6% vs. 25.7%, p=0.02, DM 14.1% vs. 7.5%, p<0.001 and PCSM 13.3% vs. 6.2%, p<0.001. In addition, events occurred faster in HRPCa patients. The 10-year (95% CI) OS and DMFS rate were significantly lower in HRPCa comparatively to IRPCa (63% (60-67) vs. 72% (69-76), p<0.001) and (60% (56-64) vs. 70% (67-74), p<0.001) respectively. There was also a significant difference in the global hazard ratio (HR) for death with higher risk in pts with HRPCa (HR (95% CI) = 1.32 (1.15-1.52), p<0.001) and for DMFS (HR= 1.37 (1.19-1.57), p<0.001). Even when adjusting for age, Zubrod, and comorbidities, outcomes continued to be significantly worse for HRPCa comparatively to IRPCa. Conclusion: In a population of localised prostate cancer treated
according to the Phoenix definition was significantly more frequent after SBRT (16/75; 21.3%) than after BQT (5/61; 8.2%) (p = 0.035). Overall survival differed significantly between groups ( p = 0.003), with more deaths observed among SBRT patients (25/75; 33%) compared to BQT (7/61; 11%). Prostate cancer–related mortality did not differ significantly between groups. Conclusion: Both LDR brachytherapy and SBRT achieved excellent long-term oncologic outcomes in patients with low- and favorable-intermediate risk prostate cancer. Although biochemical recurrence and overall mortality were higher in the SBRT group, these differences likely reflect baseline characteristics rather than true treatment efficacy. SBRT provided comparable disease control with significantly lower urinary and rectal toxicity, supporting its role as an effective, non- invasive, and well-tolerated alternative to brachytherapy. References: Pesonen S, Mäkelä P, Järvinen R, et al. Long-term efficacy and urological toxicity of low-dose-rate brachytherapy as monotherapy for localized prostate cancer: a single-center experience. Radiat Oncol. 2019;14(1):110.Kim YJ, Park JH, Lee J, et al. Long-term results and PSA kinetics after robotic stereotactic body radiotherapy for localized prostate cancer. Radiat Oncol. 2025;20(1):45.Gogineni E, Rana Z, Soberman D, et al. Biochemical Control and Toxicity Outcomes of Stereotactic Body Radiation Therapy Versus Low-Dose- Rate Brachytherapy in the Treatment of Low- and Intermediate-Risk Prostate Cancer. Int J Radiat Oncol Biol Phys. 2021;109(5). Keywords: LDR, brachytherapy, SBRT Digital Poster Highlight 1058 Outcomes comparison between intermediate and high-risk prostate cancer, using the NCCN classification; Long term results based on 2 phase III trials Abdenour Nabid 1 , Nathalie Carrier 2 , Eric Vigneault 3 , André-Guy Martin 3 , Jean-Paul Bahary 4 , Thu Van Nguyen 4 , Peter Vavassis 5 , Marc-André Brassard 6 , Boris Bahoric 7 , Robert Archambault 8 , François Vincent 9 , Redouane Bettahar 10 , Marie Duclos 11 , Derek Wilke 12 , Luis Souhami 11 1 Radiooncologie, CIUSSS de l'Estrie - CHUS, Sherbrooke, Canada. 2 Statistique, CIUSSS de l'Estrie - CHUS, Sherbrooke, Canada. 3 Radiooncologie, CHU de Québec - Université Laval, Québec, Canada. 4 Radiooncologie, Centre Hospitalier de l'Université de Montréal, Montréal, Canada. 5 Radiooncologie, Hôpital Maisonneuve-Rosemont, Montréal, Canada. 6 Radiooncologie, Centre intégré universitaire de santé et de services sociaux du Saguenay-Lac-Saint-Jean,
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