Prospective observational study to assess value of prostate specific antigen as screening test for prostate cancer

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Abstract
Objective: To evaluate measurement of serum prostate specific antigen as a potential screening test for future clinical prostate cancer among healthy men. Design: Nested case-control study with stored serum samples collected from 49261 men with follow up using national death and cancer registration systems. Subjects: 265 asymptomatic men who subsequently developed clinical prostate cancer and 1055 controls matched for age, study centre, and duration of storage of samples. Main outcome measures: Distribution of concentrations of the antigen in men who developed prostate cancer and in controls. Results: Prostate specific antigen concentrations were significantly higher in men who subsequently developed prostate cancer than in controls. In the first three years after blood collection the median concentration was 23 times greater in cases than in controls of the same age at the same centre (that is, 23 multiples of the median). A smaller difference persisted thereafter; 4.0 multiples of the median 3-6 years after blood collection, 3.6 6-10 years, and 1.8 after 10 years. In the first three years the proportion of men who developed prostate cancer and had raised levels of the antigen (>/=12 multiples of the median) (detection rate or sensitivity) was 81% (95% confidence interval 54% to 96%). The proportion of men who did not develop prostate cancer but had levels this high (false positive rate) was only 0.5%. Conclusion: Prostate specific antigen measurement is a highly discriminatory screening test for prostate cancer among healthy men. In the general population, 60-74 year old men who had >/=12 times the normal median level would have about a 50% chance of developing clinical prostate cancer in the next three years. Measurement of this antigen is a good enough screening test to justify a randomised controlled trial to determine any reduction in mortality from prostate cancer.