Even when a screening study has demonstrated a mortality reduction, the degree of pre-testing and contamination is of importance as it can dilute the "true" effect of screening. Our object was to describe the level of pre-testing and contamination in the Göteborg-1 prostate cancer (PC) screening trial.
20,000 men, 50-64 years, were invited in 1994 and randomized to either a screening group (SG) (offered prostate-specific antigen (PSA) testing every 2 yrs) or to a control group (CG). Follow-up through December 31, 2014. Outcome measurement was overall testing in the SG and CG. A positive PSA test was defined as a PSA ≥3 ng/mL.
In the study, 4.2% in the SG and 4.6% men in the CG were tested before study start. During follow-up, 72% in the CG took at least one PSA test (contamination) compared to 87% of men in the SG. Of all PSAs, 24% in the SG and 39% in the CG were above threshold. In total, 66% of the men underwent prostate biopsy within 12 months from a raised PSA in the SG and 28% in the CG.
Similar proportions of men were PSA-tested in both the SG and CG, yet only a minority of contamination PSAs led to biopsy. Also, men in the SG started screening at a younger age. These could both be explanations for our result that organized screening is more effective in reducing prostate cancer mortality than non-organized testing. When carried out properly and compared to an unscreened population, the effects of organized screening are likely even greater than previously shown in the Göteborg screening trial.
The Journal of urology. 2022 Jun 30 [Epub ahead of print]
K Stinesen Kollberg, E Holmberg, A Josefsson, J Hugosson, R Arnsrud Godtman
Department of Urology, Institute of Clinical Science, Sahlgrenska Academy, University of Gothenburg, Gothenburg Sweden., Region Västra Götaland, Sahlgrenska University Hospital, Department of Urology, Gothenborg Sweden.