An article published in The Lancet Oncology suggests that a higher incidence of screening for prostate-specific antingens in the USA is associated with a large decrease in prostate-cancer mortality in the USA compared to the UK between 1994 and 2004. Researcher Simon Collin (University of Bristol, UK) and colleagues can not be sure of the exact role that screening played until a randomized trial is conducted.
The rate of prostate cancer screening is markedly different in the USA than in the UK. The prostate-specific antigen (PSA) test is very common in the USA. Data from 2001 show 57% of men aged 50 or older having had a PSA test within the last 12 months. Across the pond in the UK, about 6% of men aged 45 to 84 had a PSA test for each year between 1999 and 2002. Researchers, however, are lacking solid evidence that routine PSA screening results in a decline of prostate-cancer mortality. Comparisons of prostate cancer trends in the USA and the UK using data from the late 1990s have demonstrated that mortality rates in the USA started to fall more quickly than rates in the UK, but there is not enough evidence to suggest that PSA screening is the reason for this difference.
Collin and colleagues studied patterns in prostate-cancer mortality in the USA and the UK between 1975 and 2004 and evaluated them alongside screening and treatment trends. The researchers found that in both countries, mortality rates were at their highest in the early 1990s and were at almost the same rate. The divergence occurs after this period, as the mortality rate decrease in the USA (4.17% per year) was about four times the rate in the UK (1.17% per year). Patients aged 75 or older in the USA saw the largest and longest lasting decline in mortality rates, but rates had stopped declining in this group in the UK by the year 2000.
One reason for the difference in mortality rates that is suggested by the authors is that the two countries could be engaging in different treatment and screening policies. In the USA, there is a greater use of gonadotropin-releasing hormone treatment in older men. Also, men with locally advanced and asymptomatic prostate cancer discovered through greater PSA testing tended to receive more aggressive treatment. A third possibility may concern difference in the way the two countries identify the cause of death in patients with prostate cancer.
“The decline in mortality from prostate cancer in the USA is striking in comparison to the UK, but we can only continue to speculate about the relative contributions of differences in detection and treatment, or the relative balance of benefits and harms, until the publication of findings from trials provides the robust evidence that is so eagerly awaited,” conclude the authors.
Prostate-cancer mortality in the USA and UK in 1975 – 2004: an ecological study
Simon M Collin, Richard M Martin, Chris Metcalfe, David Gunnell, Peter C Albertsen, David Neal, Freddie Hamdy, Peter Stephens, J Athene Lane, Rollo Moore, Jenny Donovan
The Lancet Oncology (2008).
doi:10.1016/S1470-2045(08)70104-9
Written by: Peter M Crosta