3256 - APP4-Guided Selection of Active Surveillance vs. SBRT for Favorable-Risk Prostate Cancer: Pooled Prospective Registry and Trial Outcomes
Presenter(s)
R. Del Castillo1, D. Vesprini2, P. Cheung3, C. William4, J. Detsky5, G. Morton5, S. K. Liu6, J. M. Hudson5, C. Udovicich7, L. Zhang5, C. L. Tseng8, A. Mamedov5, H. Leong9, M. Beera10, Z. Sadiq10, A. Deabreu8, M. Kulasingham-Poon8, L. Klotz11, and D. A. Loblaw12; 1Sunnybrook Health Sciences Centre, Odette Cancer Centre; Department of Radiation Oncology; University of Toronto, Toronto, ON, Canada, 2Sunnybrook Healthcare Institute, Toronto, ON, Canada, 3Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 4Durham Regional Cancer Centre, Oshawa, ON, Canada, 5Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 6Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 7GenesisCare Melbourne, Malvern, Australia, 8Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 9Sunnybrook Research Institute, Toronto, ON, Canada, 10Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 11Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 12Ontario Institute of cancer research, Toronto, ON, Canada
Purpose/Objective(s): To compare long-term freedom from metastasis and prostate cancer–specific survival in patients on active surveillance (AS) or managed with stereotactic body radiotherapy (SBRT), and to evaluate absolute percentage Gleason pattern 4/5 (APP4) =5% as a pragmatic surrogate to guide treatment selection in favorable-risk prostate cancer.
Materials/Methods: We pooled a single-institution prospective AS registry and four prospective SBRT trials. Time to event endpoints were measured from first biopsy date. Outcomes included freedom from metastasis (FFM) and cancer-specific survival (CSS) using Kaplan–Meier methods and biochemical failure (BF) using Nelson–Aalen estimates. Analyses compared AS versus SBRT descriptively and stratified patients by APP4 (<0.1%, 0.1–5%, >5%).
Results: The combined cohort included 1,603 men (AS n=1,404; SBRT n=199). At 10 years, FFM was 97.2% for AS and 94.6% for SBRT (log-rank p=0.066), while CSS was 98.5% and 98.1%, respectively (p=0.693). Among men with available APP4 (n=921), APP4 strongly stratified outcomes: 10-year cumulative BF was 7.0% (APP4 <0.1%), 18.4% (0.1–5%), and 27.9% (>5%) (p<0.0001). Corresponding 10-year FFM was 98.7%, 92.0%, and 88.6% (p<0.0001). Across analyses, APP4 >5% consistently identified men with higher failure and metastasis risk, whereas APP4 =5% demonstrated excellent long-term metastasis control comparable to low-risk disease biology.
Conclusion: Both AS and SBRT yield excellent long-term metastasis and cancer-specific outcomes in favorable-risk prostate cancer. APP4 provides clinically actionable risk discrimination: APP4 =5% supports AS as a safe option, while APP4 >5% can prioritize definitive therapy to mitigate higher failure or metastasis risk.