Number of screens for overdetection as an indicator of absolute risk of overdiagnosis in prostate cancer screening

As with wide-spread use of prostate cancer (Pca) screening with prostate-specific antigen testing, overdetection has increasingly gained attention. The authors aimed to estimate absolute risk of overdetection (RO) in Pca screening with various interscreening intervals and ages at start of screening. We estimated age-specific preclinical incidence rates (per 100,000 person-years) for progressive cancer (from 128 for age group 55-58 years to 774 for age group 67-71 years) and nonprogressive cancer (from 40 for age group 55-58 years to 66 for age group 67-71 years), the mean sojourn time (7.72 years) and the sensitivity (42.8% at first screen and 59.8% at the second screen) by using a multistep epidemiological model with data from the Finnish randomized controlled trial. The overall number of screens for overdetection (NSO) was 29 (95% confidence interval (CI): 18, 48) for screenees aged 55-67 years, equivalent to 3.4 (95% CI: 2.1, 5.7) overdetected Pcas per 100 screenees. The NSO decreased from 63 (95% CI: 37, 109) at the first screen to 29 (95% CI: 18, 48) at the third screen and from 43 (95% CI: 36, 52) for age 55 years to 25 (95% CI: 8, 75) at age 67 years at the first screen. In conclusion, around 3.4 cases for every 100 screened men would be overdetected during three screen rounds (∼ 13 years of follow-up) in the Finnish randomized controlled trial. Elucidating the absolute RO under various scenarios makes contribution for evaluating the benefit and harm of Pca screening.