Screening for prostate -specific antigen (PSA) leads to a small or no reduction in prostate cancer mortality, but is associated with harm related to both evaluation and treatment, concluded a review of studies published in the Annals of Internal Medicine. Last Friday's publication of the paper came the day after recommendations from the US Preventive Services Task Force had been leaked to the press, stating men should no longer undergo annual PSA tests.
In the study Roger Chou and colleagues from Oregon Health & Science University (Portland, Oregon) identified published papers that helped to synthesise current evidence on screening and treatments for localised prostate cancer. Altogether the team identified five clinical trials that sought to assess whether men who underwent routine PSA tests were less likely to die of prostate cancer, three of which were judged to be weak.
The two stronger studies - both published in March 2009 in The New England Journal of Medicine – produced conflicting results. The ERSPC (European Randomised Study of Screening for Prostate Cancer) study found that a prespecified subgroup (of men aged 55 to 69years) showed a 20% reduction in relative risk for mortality after nine years in men who had been screened. However, the PLCO (US Prostate, Lung, Colorectal and Ovarian screening) study found no significant difference after 10 years between those groups who had been screened and those who had not.
Other studies explored by the investigators showed that overall 12 to 13% of screened men had false-positive results, and that serious infections or urinary retention occurred in 0.5% to 1.0% of prostate biopsies.
From the studies examined, the investigators estimate that the treatment of three men with prostatectomy or seven men with radiation therapy in place of "watchful waiting" resulted in one additional case of erectile dysfunction in each case, ant that treating five men with prostatectomy resulted in one additional case of urinary incontinence.
"In summary, PSA-based screening is associated with detection of more prostate cancers; small to no reduction in prostate cancer-specific mortality after 10 years; and harms related to false positive test results, subsequent evaluation, and therapy, including over diagnosis and overtreatment," write the authors.
They add that the results from the upcoming Prostate Cancer Intervention versus observation trial, which compared prostatectomy with watchful waiting for screening-detected cancer, should help to clarify which patients would most benefit from prostatectomy, with the potential to reduce harms from unnecessary treatment.
R Chou, J Croswell, T Dana, et al. Screening for Prostate Cancer: A review of the evidence for the U.S. Preventive Services Task Force. Annals of Internal Medicine 2011.