Background
One of the problems with prostate-specific antigen (PSA) testing for prostate cancer is that of over-treatment, that is, diagnosing and treating cancers (with potentially serious side-effects) that are not likely to ever cause symptoms or shorten life.
This is of particular relevance to older men with life expectancies of 10-20 years who may not benefit from having prostate cancers detected at this stage of their lives.
Aim
To determine the relationship between concentrations of PSA at age 60 and subsequent diagnosis of clinically relevant prostate cancer in an unscreened population, to evaluate whether screening for prostate cancer and chemoprevention could be stratified by risk.
Methods
Results
The rate of screening during the course of the study was low and no cancers were detected by screening. There were 43 cases of metastasis and 35 deaths from prostate cancer.
Concentration of prostate specific antigen at age 60 was associated with prostate cancer metastasis (area under the curve 0.86, 95% confidence interval 0.79 to 0.92; P<0.001) and death from prostate cancer (0.90, 0.84 to 0.96; P<0.001).
The greater the number for the area under the curve (values from 0 to 1) the better the test.
Although only a minority of the men with concentrations in the top quartile (>2 ng/ml) develop fatal prostate cancer, 90% (78% to 100%) of deaths from prostate cancer occurred in these men.
Conversely, men aged 60 with concentrations at the median or lower (</=1 ng/ml) were unlikely to have clinically relevant prostate cancer (0.5% risk of metastasis by age 85 and 0.2% risk of death from prostate cancer).
Conclusion
The concentration of prostate specific antigen at age 60 predicts lifetime risk of metastasis and death from prostate cancer.
Though men aged 60 with concentrations below the median (</=1 ng/ml) might harbour prostate cancer, it is unlikely to become life threatening. Such men could be exempted from further screening, which should instead focus on men with higher concentrations.
