Tests for prostate cancer ‘risky and of little use’
Posted Saturday, March 28 2009 at 15:11
The blood test used to screen for prostate cancer saves very few lives. And it leads to risky and unnecessary treatments for large numbers of men, two studies have found.
The findings, the first based on rigorous, randomised studies, confirm some long-standing concerns about the wisdom of widespread prostate cancer screening.
Although the studies are continuing, results so far are considered significant and the most definitive to date.
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 tumour.
But it has been difficult to know whether finding prostate cancer early saves lives.
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.
The studies — one in Europe and the other in the United States — are “some of the most important studies in the history of men’s health,” said Dr Otis Brawley, the chief medical officer of the American Cancer Society.
In the European study, 48 men were told they had prostate cancer and were needlessly treated for it.
Dr Peter B. Bach, a physician and epidemiologist at Memorial Sloan-Kettering Cancer Centre, says one way to think of the data is to suppose he has a PSA test today. It leads to a biopsy that reveals he has prostate cancer, and he is treated for it.
There is a one in 50 chance that, in 2019 or later, he will be spared death from a cancer that would otherwise have killed him. And there is a 49 in 50 chance that he will have been treated unnecessarily for a cancer that was never a threat to his life.
Prostate cancer treatment can result in impotence and incontinence when surgery is used to destroy the prostate, and, at times, painful defecation or chronic diarrhoea when the treatment is radiation.
As soon as the PSA test was introduced in 1987, it became a routine part of preventive health care for many men age 40 and older.
Experts debated its value, but their views were largely based on less compelling data that involved statistical modelling and inferences.
Now, with the new data, cancer experts said men should carefully consider the possible risks and benefits of treatment before deciding to be screened. Some may decide not to be screened at all.
For years, the cancer society has urged men to be informed before deciding to have a PSA test. “Now we actually have something to inform them with,” Dr. Brawley said. “We’ve got numbers.”