ESTRO 2025 - Abstract Book

S2018

Clinical - Urology

ESTRO 2025

2901

Digital Poster Identifying Intermediate Risk Prostate Cancer Patients Appropriate for Active Surveillance using Recursive Partitioning Analysis. Ruben Del Castillo 1,2 , Danny Vesprini 1,2 , Stanley Liu 1,2 , Hon Leong 3 , Mona Beera 3 , Liying Zhang 1 , Alexander Mamedov 1 , Zeeba Sadiq 1 , Meghan Kulasingham-Poon 1 , Laurence Klotz 4,3,5 , Loblaw Andrew 1,2,6 1 Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada. 2 Radiation Oncology, University of Toronto, Toronto, Canada. 3 Research Institute, Sunnybrook Research Institute, Toronto, Canada. 4 Urology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada. 5 Urology, University of Toronto, Toronto, Canada. 6 Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada Purpose/Objective: A number of guideline groups recommend active surveillance (AS) for patients with low-risk prostate cancer as well as selected patients with intermediate-risk prostate cancer (IRPC) – these groups are not well defined. Our group has previously shown that some patients with IRPC have high rates of progression to advanced disease. The goal of this study was to determine a subset of patients with IRPC where AS is safe.

Material/Methods:

This single-institution, phase II study enrolled men with low-risk and selected IRPC patients since 1995. Patients were followed with PSA every 3-6 months, DRE every 6 months with repeat systematic biopsies at 1 year and every 3 years. Since 2013, MRI staging has been done every 2 years with targeted and systematic biopsies done for new or growing lesions. Recursive Partitioning Analysis (RPA) was applied to identify key factors influencing freedom from metastasis (FFM). Patients were followed until death or withdrawn consent. Time to treatment, FFM, cause-specific survival (CSS), and overall survival were calculated from the date of registration biopsy.