Do the benefits of screening for prostate cancer outweigh the risks?

Each year in the UK about 34,000 men are diagnosed with prostate cancer and over 10,000 die from the disease. Two new studies of prostate cancer screening reported in the New England Journal of Medicine (26th March 2009) have shown equivocal results. The question of whether the benefits of screening to prevent death from prostate cancer outweigh the risks of unnecessary treatment remains unanswered.

The first trial, a multi-centre American study of 77,000 men ages 55 to 74, found that the rate of death from prostate cancer was low and did not differ significantly between groups receiving annual screening and usual care. The American Prostate, Lung, Colorectal, and Ovarian Cancer trial randomised men either to annual PSA testing for six years plus annual digital rectal examination for four years, or to no screening. After 10 years, the researchers found 92 prostate cancer deaths in the screening group and 82 in the control group, a chance difference.

In the second study of 182,000 men aged 50 to 74 from seven European countries, PSA-based screening reduced the rate of death from prostate cancer by 20%, which was just slightly more than a chance difference between the two groups. However, this reduction in death rate was associated with a high risk of over-diagnosis, that is, diagnosing cancer in men who would not have clinical symptoms during their lifetime because their tumours were small and slow-growing. Over-diagnosis was estimated to be as high as 50% in the screening group, resulting in unnecessary treatment and side-effects such as incontinence and impotence. The authors commented "Although the results of our trial indicate a reduction in prostate-cancer mortality associated with PSA screening, the introduction of population-based screening must take into account population coverage, over-diagnosis, over-treatment, quality of life, cost, and cost-effectiveness."

Both studies had important limitations. For example, in the US study, screening was actually completed in about 85% of those assigned screening but in only about 50% of control subjects. In the European trial, results were pooled from seven countries whose PSA screening intervals and inclusion of rectal examination in initial screening varied.

The current UK approach to prostate cancer, the Prostate Cancer Risk Management Programme, is designed so that men who are concerned about the risk of prostate cancer can receive clear and balanced information about the advantages and disadvantages of the PSA test and of treatment for prostate cancer to help them decide whether they want to have the test.

Tests: PSA
Conditions: Prostate cancer
Screening: Prostate cancer - Adults, Prostate cancer - Adults 50 and up