April 1, 2011
Screening Does Not Reduce Prostate Cancer Deaths
Research: Randomized prostate cancer screening trial: 20 year follow-up
Screening does not significantly reduce prostate cancer deaths, but the risk of overdetection and overtreatment is considerable, concludes a 20-year study published on bmj.com today.
Prostate cancer is one of the most common cancers among men worldwide. Screening is widely used in many countries, but remains controversial because experts can't agree whether the benefits outweigh the potential harms and costs of overdiagnosis and overtreatment of healthy men.
Today's findings are based on a trial started in Sweden in 1987 involving 9,026 men aged 50-69 years identified in the National Population Register.
From this population, 1,494 men were randomly selected for screening every third year from 1987 to 1996. The remaining 7,532 men acted as controls.
On the first two occasions, screening was done by digital rectal examination only. From 1993, this was combined with prostate specific antigen (PSA) testing. On the fourth occasion (1996), only men aged 69 or under at the time of the investigation were invited.
All men with cancer diagnosed up to December 31, 1999 were included in the analysis. Survival was followed until December 31, 2008.
There were 85 cases (5.7%) of prostate cancer diagnosed in the screened group and 292 (3.9%) in the control group. The tumours in the screening group were smaller and more often localised than in the control group.
Analysis did not show significantly longer survival or overall survival for men with prostate cancer in the screened group compared with the control group.
And while screening and treating men with detected tumours might reduce deaths specifically from prostate cancer by up to a third (at best), this would be at considerable risk of worrying overdetection and unpleasant or harmful overtreatment. Indeed, a previous trial found that to prevent one death from prostate cancer, 1,410 men would need to be screened and 48 treated.
The authors believe that men should be fully informed about the potential hazards of treatment, and the psychological effects of false-positive test results, before they are screened.
They also argue that the next goal for prostate screening should be to find ways of discriminating slow-growing (indolent) tumours from high risk tumours and to develop less aggressive treatment for indolent tumours, rather than to optimise sensitivity of the diagnostic tests.
"After 20 years of follow-up, the rate of death from prostate cancer did not differ significantly between men in the screening group and those in the control group," they conclude. Results from randomised controlled trials of prostate cancer screening have been published in recent years, but none with 20 years of follow-up, they add. Long follow-up is necessary to draw definite conclusions about the benefits of screening.
On the Net: