Evidence of Benefit
The absolute difference between the screening and control groups was 0.71 prostate-cancer deaths per 1,000 men. Thus, in order to prevent one prostate-cancer death, the number of men who would need to be screened would be 1,410. The additional prostate cancers diagnosed by screening resulted in an increase in cumulative incidence of 34 per 1,000 men, so that 48 additional subjects would need to be treated to prevent one death from prostate cancer. Thus, PSA-based screening reduced the rate of death from prostate cancer by 20% but was associated with a high risk of overdiagnosis.
Important information that was not reported includes the contamination rate in the control group, and the treatment administered to the prostate cancer cases by stage and by randomly assigned group. Incompleteness of data is also a concern because it appears that several of the participating countries have not yet provided data beyond the 10-year point at which the major effect appears to occur. Longer follow-up will be needed to determine the final results of this trial.
The Goteborg (Sweden) trial is a prospective randomized trial of 20,000 men born between 1930 and 1944. Data from participants born between 1930 and 1939 is used in the pooled ERSPC data. Recently, data with up to 14 years of follow-up was reported. Of the screened group, 12.7% was diagnosed with prostate cancer versus 8.2% of the control group. The absolute risk of prostate death was 0.9% in the control group and 0.5% in the screening group (95% CI, 0.17-0.64). This is a 44% RR reduction in prostate-cancer mortality (95% CI, 0.28-0.68; P = .0002). Of note, the number of deaths from all causes was equal in the intervention group and the control group. The authors estimated that 12 men needed to be diagnosed and treated to prevent one death.
The Norrkoping study (Sweden) is a population-based nonrandomized trial of prostate cancer screening. All men aged 50 to 69 years living in Norrkoping, Sweden in 1987 were allocated to either invited (every sixth man allocated to invited group) or not-invited groups. The 1,494 men in the invited group were offered screening every 3 years from 1987 to 1996. The first two rounds were by DRE; the last two rounds by both DRE and PSA. About 85% of men in the invited group attended at least one screening; contamination by screening in the not-invited group (n = 7,532) was thought to be low. After 20 years of follow-up, the invited group had a 46% relative increase in prostate cancer diagnosis. Over the period of the study, 30 men (2%) in the invited group died of prostate cancer, compared with 130 (1.7%) men in the not-invited group. The RR of prostate cancer mortality was 1.16 (95% CI, 0.78-1.73). This nonstatistically significant finding provides no evidence that screening leads to a reduction in prostate cancer mortality, even after 20 years of follow-up.