Reducing overtreatment of prostate cancer by radical prostatectomy in Eastern Ontario: a population-based cohort study.

Background: Canadian guidelines recommend against population-based screening for prostate cancer because of the risk of overdiagnosis and overtreatment. We sought to assess whether a higher proportion of patients receiving surgery had clinically significant cancer over time.

Methods: All hospitals in Eastern Ontario that perform prostatectomy participate in a Prostate Cancer Community of Practice, which prospectively maintains a database for the region. Using these data, we conducted a retrospective cohort study that included all patients who underwent prostatectomy from 2009 to 2015 in the region. We examined trends in biopsy findings, clinical stage, prostate-specific antigen level and Gleason score. We then determined whether the proportion of patients with clinically significant cancer (Gleason score ≥ 7 or stage pT3) increased over time.

Results: During the study period, 1897 patients underwent prostatectomy in Eastern Ontario (mean 271 surgeries/yr). The proportion of patients who were determined to have National Comprehensive Cancer Network intermediate or high-risk disease increased from 46.7% in 2009 to 90.2% in 2015. The proportion of men with clinically significant cancer on prostatectomy increased from 59.7% in 2009 to 93.1% in 2015. Adjusted analyses suggested that the proportion of patients with clinically significant cancer increased by 5% per year during the study period.

Interpretation: There has been a change in the tumour characteristics of patients who undergo prostatectomy in Eastern Ontario. In recent years, almost all patients have had clinically significant cancer, which suggests that overtreatment of prostate cancer has decreased.