Two large studies published online last week in the New England Journal of Medicine have found that the PSA blood test used to screen for prostate cancer saves few lives and can lead to risky and unnecessary treatments for 95% of the men who are screened.
The PSA (prostate-specific antigen) test, which measures a protein released by prostate cells, does what it is supposed to do — indicates a cancer might be present, leading to biopsies to determine if there is a tumor. Most of the cancers tend to grow very slowly and are never a threat and, with the faster-growing ones, even early diagnosis might be too late. Until the release of the results of the two new studies, it has been difficult to know whether finding prostate cancer early saves lives. Both studies have confirmed that in most instances it does not.
The findings, which are the first based on robust, independently audited evidence, and randomized studies, confirmed some longstanding concerns about the wisdom of prostate screening and indicated that the practice of widespread prostate screening may result in far more harm than benefits. Prostate cancer treatment can result in impotence and incontinence when surgery is used to destroy the prostate, and, at times, painful defecation or chronic diarrhea when the treatment is radiation. In addition, many believe that the practice of cancer biopsies often leads to the spread and more rapid development of cancer.
The European study, the European Randomized Study of Screening for Prostate Cancer (ERSPC), commenced in the early 1990's and involved 182,000 men in eight countries – Belgium, Finland, France, Italy, Netherlands, Spain, Sweden and Switzerland – with an overall follow-up of up to 12 years. The other study, by the National Cancer Institute, involved nearly 77,000 men at 10 medical centers in the United States. Although both studies are continuing, the results so far are considered significant and the most definitive to date.
In both studies, participants were randomly assigned to be screened — or not — with the PSA test and in each study the two groups were followed for more than a decade while researchers counted deaths from prostate cancer, asking whether screening made a difference.
In the European study, for every man whose death was prevented within a decade of having a PSA test 48 men were told they had prostate cancer and needlessly treated for it, and the study found that there were only seven fewer prostate cancer deaths for every 10,000 men screened and followed for nine years.
The American study, found no reduction in deaths from prostate cancer after most of the men had been followed for 10 years. Instead, by seven years the death rate was 13 percent lower for the unscreened group.
Sources Included: NY Times, NEJM, ScienceDaily