Screening for Prostate Cancer
At the present time there is pressure to screen for prostate cancer, but implementation of screening programmes for prostate cancer cannot be recommended based on the available evidence. The main reason for this situation is that no results are available from randomised trials assessing screening for prostate cancer. These are the only methods of evaluation which avoid bias and, in consequence, it is not known whether screening by one of the available modalities or in combination is effective in leading to a reduction in the mortality rate from prostate cancer. This is a necessary prerequisite for embarking on population screening.
Any reduction in mortality from prostate cancer due to screening, while uncertain, must be weighed against the harm from screening diagnosis and treatment. Some men who do not need treatment are likely to receive it. These are men destined to die of causes other than prostate cancer. Unfortunately, at diagnosis, men needing treatment for prostate cancer cannot be differentiated from men who do not.
The PSA test is simple, cheap, readily available and acceptable. PSA testing has already achieved a high penetration among men and their physicians. To document the extent of PSA testing in the general population at Getafe (Spain) a total of 5.371 PSA test records (1997–1999) were reviewed and testing rates estimated per 1.000 person-years. The PSA-testing rate in the general population was 21.6/1000 person-years. In the age-group 55–69 years, this rate was 86.8/1000 and increased to 152.6/1000 in men >70 years. In Milan, Italy where there is no campaign publicising or encouraging prostate cancer screening, it has been estimated that 26.9% of men aged 40 and older and without a history of prostate cancer received a PSA test in the 2-year period 1999–2000. In men aged 50 and greater, this rate rose to 34%.
Multiple sources of data show that prostate cancer incidence rates rose following the introduction of PSA testing. The average age at diagnosis has fallen, the proportion of advanced stage tumours has declined, the proportion of moderately differentiated tumours has increased, and patterns of care have changed accordingly. A decline in mortality began in the USA and other countries in 1991. The decline in mortality is well established, but this recent trend may only retrace an increase in mortality that immediately preceded it. The descriptive epidemiology of prostate cancer reveals many effects of the introduction of prostate cancer screening. Although the evidence suggests increased prostate cancer testing has yielded public health benefit, this has not yet been shown conclusively and a decision on the value of screening should await the results of trials. In any event, systems should now be in place to ensure that men and physicians participating in PSA testing participate in a programme in which the effect of the intervention can be evaluated as best can be done given the non-experimental nature of the intervention.