3212 - Identifying Intermediate-Risk Prostate Cancer Patients Appropriate for Active Surveillance Using Recursive Partitioning Analysis and Long-Term Follow-up
Presenter(s)
R. Del Castillo1, D. Vesprini2,3, S. K. Liu3, H. Leong4, M. Beera5, Z. Sadiq5, L. Zhang6, A. Mamedov6, M. Kulasingham-Poon7, L. Klotz8, and D. A. Loblaw6,9; 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, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 4Sunnybrook Research Institute, Toronto, ON, Canada, 5Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 6Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 7Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 8Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 9Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada
Purpose/Objective(s): 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.
Materials/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 Patients were followed until death or withdrawn consent.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.
Results: The study initially included 1409 men, of whom 25 were excluded due to Gleason categories 4+3 or 4+4, leaving 1384 patients analyzed. With a median follow-up of 11.2 years (range 1.2–26.4 years), the RPA identified MRI use, Gleason grade (GG), PSA levels, and APP4 categories as critical predictors of FFM. Patients with GG1 and PSA <10 exhibited excellent outcomes, with 15-year FFM rates exceeding 98%. For GG2 patients, those with APP4 <1 had significantly better outcomes compared to those with APP4 =1, who demonstrated increased risk of metastasis (HR 2.9). Notably, APP4 =1 categories were combined due to a low number of patients with APP4 >5 in the MRI subgroup.
Conclusion: Patients with GG1 and PSA <10 or GG2 with APP4 <1 have low risk of metastases and prostate cancer-specific mortality, making them ideal candidates for active surveillance. Conversely, GG2 and APP4 =1 patients may require closer monitoring or definitive treatment. These findings enhance risk stratification in IRPC and support personalized management strategies for safe AS application.