Evaluating the Impact of Age on Prostate Cancer Overdiagnosis Using Long‐Term Follow‐Up From the <scp>CAP</scp> Randomised Trial

Prostate cancer overdiagnosis is detection of prostate cancer through PSA testing that otherwise would not have been diagnosed within the patient's lifetime. It is a major concern to policymakers due to its impact on quality of life. We used long-term follow-up data from the CAP randomised trial of a one-off screen, and English male competing mortality rates (2021-23), to estimate the impact of age on excess prostate cancer incidence within 15 years ('overdiagnosis') using competing-risks methods. In total, 2249 (1.19%) of 189,386 men invited for a PSA test in CAP had cancer detected at the one-off screen. Prostate cancer cumulative incidence at 15 years was 7.08% (95% CI 6.95%-7.21%) in those invited to screening, compared with 6.94% (95% CI 6.82%-7.06%) in the control arm; an absolute excess incidence difference of 0.14% (95% CI -0.04% to 0.37%). Excess net incidence to 15 years was 0.14/1.19 = 11.7% (95% CI 0.0%-26.7%) of cases detected at a single prevalent screen. Accounting for competing mortality, men diagnosed at screening aged 50 years were projected to have a 16% chance the cancer would not have been detected within 15 years, rising to 32% if detected at screening aged 70 years and 58% aged 80 years. Thus, prostate cancer overdiagnosis rises substantially with age due to competing mortality, and is relatively low for younger men. Accordingly, policies that enable opportunistic testing should be re-examined in settings where they have led to high rates of screening in older men.