Screening with prostate specific antigen and metastatic prostate cancer risk: A population-based case-control study

Abstract

4651 Background: Screening of asymptomatic men with the prostate specific antigen (PSA) is a highly controversial issue. There is little evidence to date that such screening is effective in reducing mortality from prostate cancer. We conducted a population-based case-control study to determine if screening with PSA reduces the risk of metastatic prostate cancer. Methods: The study was carried out in Metropolitan Toronto and five surrounding counties in Ontario, Canada. Cases were men diagnosed with metastatic prostate cancer between August 1, 1999 and May 31, 2002. Controls were randomly sampled from the source population and matched to cases for age, area of residence, and observation time. Medical records and a self-administered questionnaire were used to collect the data. We obtained information on PSA testing, digital rectal exams, symptoms, comorbidity, use of health services, as well as known and suspected risk factors for prostate cancer. Analyses were performed on 236 cases and 462 controls. Results: After adjustment for observation time, the frequency of screening among asymptomatic men was 24.6% in the cases and 33.1% in the controls (odds ratio 0.66, 95% confidence interval 0.47 to 0.92). Self-reported screening was also significantly less frequent among the cases (odds ratio 0.48, 0.34 to 0.67). No significant confounding was found in multiple logistic regression analyses. Secondary analyses including symptomatic and asymptomatic men showed that the cases generally had fewer symptoms and fewer PSA tests than the controls, except for the last year before the diagnosis of prostate cancer. In symptomatic men, the association between PSA testing and metastatic prostate cancer was not significant. Conclusions: The results suggest that screening of asymptomatic men with PSA may substantially reduce the risk of metastatic prostate cancer. Further research is needed to confirm these results in a randomized trial and to assess the economic and quality of life aspects of PSA screening. No significant financial relationships to disclose.