The Finnish prostate cancer screening trial: analyses on the screening failures

Prostate cancer (PC) screening with prostate-specific antigen (PSA) has been shown to decrease PC mortality in the European Randomized Study of Screening for Prostate Cancer (ERSPC). However, in the Finnish trial, which is the largest component of the ERSPC, no statistically significant mortality reduction was observed. We investigated which had the largest impact on PC deaths in the screening arm: non-participation, interval cancers or PSA threshold. The screening (SA) and control (CA) arms comprised altogether 80,144 men. Men in the SA were screened at four-year intervals and referred to biopsy if the PSA concentration was ≥ 4.0 ng/ml, or 3.0-3.99 ng/ml with a free/total PSA ratio ≤ 16%. The median follow-up was 15.0 years. A counterfactual exclusion method was applied to estimate the effect of three subgroups in the SA: the non-participants, the screen-negative men with PSA ≥ 3.0 ng/ml and a subsequent PC diagnosis, and the men with interval PCs. The absolute risk of PC death was 0.76% in the SA and 0.85% in the CA; the observed hazard ratio (HR) was 0.89 (95% confidence interval (CI) 0.76-1.04). After correcting for non-attendance, the HR was 0.78 (0.64-0.96); predicted effect for a hypothetical PSA threshold of 3.0 ng/ml the HR was 0.88 (0.74-1.04) and after eliminating the effect of interval cancers the HR was 0.88 (0.74-1.04). Non-participating men in the SA had a high risk of PC death and a large impact on PC mortality. A hypothetical lower PSA threshold and elimination of interval cancers would have had a less pronounced effect on the screening impact.