Tumor characteristics in a population-based prostate cancer screening trial with prostate-specific antigen.

Early diagnosis of prostate cancer is a necessary, but not sufficient, prerequisite for an effective screening program aiming at mortality reduction. We compared tumor characteristics between the screening and control arms in the Finnish population-based screening trial.The Finnish trial is the largest component in the European Randomized Study of Screening for Prostate Cancer. A total of 24,000 men aged 55-67 years were randomized to the screening arm, whereas 35,973 men formed the control arm during the first three screening years. At the time of invitation, 22,732 men were eligible for screening, and 15,685 (69%) participated. A prostate-specific antigen (PSA) concentration of > or ==" BORDER="0">4 micro g/liter was defined as a screening-positive finding.The detection rate among screenees was 2.4% (377 of 15,685), whereas 0.6% (40 of 7,047) of nonparticipants in the screening arm and 0.3% (112 of 35,973) of the controls were diagnosed with prostate cancer during the first postrandomization year in the absence of screening. In the screening arm, 82% of the cancers were clinically organ confined compared with 65% in the control arm. Yet, both the absolute number and cumulative incidence of advanced cancer were higher in the screening arm. No differences were seen in the WHO grade distribution between the study groups. The median PSA was substantially lower among screen-detected cases (7.1 micro g/liter) than among nonattenders (15.7 micro g/liter) and controls (13.2 micro g/liter).Our findings on intermediate indicators of PSA screening provide encouraging, yet inconclusive evidence for eventual mortality reduction.