Results from two major studies have recently been reported in the prestigious New England Journal of Medicine on the effectiveness of PSA testing as a potential population-wide screening method for prostate cancer. Unfortunately, both these studies were published prematurely which means that final results from these large studies are yet to be determined so the dilemma of PSA screening for prostate cancer remains unresolved at this time.
The first study1 (162,000 men) on prostate cancer screening was conducted in Europe (across eight countries) on men aged between 55 and 69, and established a 20% reduction in the death rate. This means that to prevent the one death, 1410 men would need to be screened for prostate cancer by PSA testing, and an additional 48 men would have to undergo treatment. This study noted that although there was a reduction in the rate of death, it was associated with a high risk of over diagnosis, meaning that many men would be having unnecessary treatment.
The second study2 (76,693 men) was conducted in America and found no significant effect of prostate cancer screening on the death rate from prostate cancer. The authors also found a low prostate cancer mortality rate which they suggested may be due to advances in medical treatment. Both studies highlighted the issue of over diagnosis as a result of screening and the consequent interventions (and side effects) that would not occur otherwise.
Methodological limitations in both studies were acknowledged. Limitations of the study include potential contamination of the control group, because half of these men in the US study had had a PSA test. The European study integrated trials from different countries where different protocols were used across the sites. The studies highlight the difficulty in conducting controlled clinical trials on prostate cancer screening, because a greater awareness of prostate cancer had increased the rates of PSA testing in the community. Further studies are underway which will add to our understanding of the effects of prostate cancer screening using the PSA test.
The results of these studies are relevant to Australian clinical practice and provide the best evidence to date that there is a significant level of uncertainty about the use of PSA test as a population-wide screening marker for prostate cancer.There are many reasons why a doctor may recommend, or a man may request, PSA testing. At an individual level, men need to be properly informed about the benefits and limitations associated with the PSA test and the implications of the results that may show normal or abnormal PSA levels.
The studies highlight that newer and more specific prostate cancer markers are needed before an effective population-wide prostate cancer screening program could be recommended or implemented.
1. Schroder FH et al. Screening and Prostate-Cancer Mortality in a Randomized European Study. N Engl J Med. 2009; 360 1320 - 1328
2. Andriole GL et al. Mortality Results from a Randomized Prostate-Cancer Screening Trial. N Engl J Med. 2009; 360: 1310-1319
