Background
Prospective single-institution active surveillance cohort (University of Toronto, Sunnybrook). 993 patients with favorable-risk prostate cancer (Gleason ≤6 and PSA ≤10 ng/mL in 73%, clinical stage T1–T2a) enrolled 1995–2014. Protocol: PSA q3 months ×2 years then q6 months, DRE q6 months, confirmatory biopsy at 1 year then q3–4 years, PSA doubling-time calculation. Intervention triggered by Gleason ≥4+3, PSA doubling time <3 years, or patient/physician preference.
Interventions and follow up
Strategy: Active surveillance with deferred curative-intent treatment on progression criteria (n=993)
Monitoring: Serial PSA, DRE, and protocol biopsies; PSA doubling-time tracking
Primary endpoint: Cause-specific and overall survival
Median follow up: 6.4 years; 15-year outcomes reported
Monitoring: Serial PSA, DRE, and protocol biopsies; PSA doubling-time tracking
Primary endpoint: Cause-specific and overall survival
Median follow up: 6.4 years; 15-year outcomes reported
Results
15-year overall survival: 78.6%
15-year cause-specific survival: 97.2% (15 of 993 prostate cancer deaths = 1.5%)
Metastatic disease at 15 years: 2.8%
15-year treatment-free survival: 38% (62% converted to treatment)
Median time to conversion: 6.5 years (IQR 3.7–9.4)
15-year cause-specific survival: 97.2% (15 of 993 prostate cancer deaths = 1.5%)
Metastatic disease at 15 years: 2.8%
15-year treatment-free survival: 38% (62% converted to treatment)
Median time to conversion: 6.5 years (IQR 3.7–9.4)
Adverse events
Biopsy-related: Prostatitis ~4%, hematuria ~2%, urinary retention ~1%
Psychological/treatment burden: Surveillance-related anxiety is an important patient-reported issue not captured in this analysis; treatment-related toxicities accrued as patients converted to radical therapy
Psychological/treatment burden: Surveillance-related anxiety is an important patient-reported issue not captured in this analysis; treatment-related toxicities accrued as patients converted to radical therapy
Conclusions
Active surveillance is safe for favorable-risk prostate cancer, with 15-year cause-specific survival of 97.2% and low metastatic progression (2.8%); about 38% remain on surveillance at 15 years without treatment. These data establish active surveillance as the preferred initial strategy for low-risk disease, avoiding overtreatment in men who would never develop clinically significant cancer.
Key Limitations
Single-institution, non-randomized — favorable outcomes partly reflect selection (low-risk disease, compliant follow-up). Gleason grading has evolved (ISUP grade groups); historical Gleason ≤6 = ISUP 1. The serial-biopsy protocol predates MRI-targeted biopsy, which may improve reclassification. Larger national datasets suggest somewhat higher reclassification and conversion rates than this cohort.
Clinical Context
The Klotz Toronto series is the most mature prospective active surveillance cohort and remains foundational evidence for surveillance as standard of care in low-risk (ISUP grade group 1) prostate cancer. ESMO, EAU, and AUA/ASTRO recommend active surveillance for low-risk disease. Modern protocols add baseline mpMRI and MRI-guided targeted biopsy to detect higher-grade disease earlier, improving risk stratification over the systematic biopsy approach used here.
References