Prostate (PSA) Test Found to Save Few Lives two large studies have found.
- From: J <xewsnswex@nalid;"no>
- Date: Thu, 19 Mar 2009 04:50:04 -0500
http://www.nytimes.com/2009/03/19/health/19cancer.html?_r=1
Prostate Test Found to Save Few Lives
By GINA KOLATA
Published: March 18, 2009
The PSA blood test, used to screen for prostate cancer, saves few lives
and leads to risky and unnecessary treatments for large numbers of men,
two large studies have found.
Mortality Results from a Randomized Prostate-Cancer Screening Trial (The
New England Journal of Medicine)
Screening and Prostate-Cancer Mortality in a Randomized European Study
(The New England Journal of Medicine)
The findings, the first based on rigorous, randomized studies, confirm
some longstanding 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 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. 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
needlessly treated for it for every man whose death was prevented within a
decade after having had a PSA test.
Dr. Peter B. Bach, a physician and epidemiologist at Memorial
Sloan-Kettering Cancer Center, 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 diarrhea 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
often involved statistical modeling 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.?
The publication of data from the two new studies should change the
discussion, said Dr. David F. Ransohoff, an internist and cancer
epidemiologist at the University of North Carolina. ?This is not relying
on modeling anymore,? he said. ?This is not some abstract, pointy-headed
exercise. This is the real world, and this is real data.?
Dr. H. Gilbert Welch, a professor of medicine at Dartmouth who studies
cancer screening, also welcomed the new data. ?We?ve been waiting years
for this,? he said. ?It?s a shame we didn?t have it 20 years ago.?
Both reports were published online Wednesday by The New England Journal of
Medicine. One involved 182,000 men in seven European countries; the other,
by the National Cancer Institute, involved nearly 77,000 men at 10 medical
centers in the United States.
In both, participants were randomly assigned to be screened ? or not ?
with the PSA test, whose initials stand for prostate-specific antigen. 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.
The European data involved a consortium of studies with different designs.
Taken together, the studies found that screening was associated with a 20
percent relative reduction in the prostate cancer death rate. But the
number of lives saved was small ? seven fewer prostate cancer deaths for
every 10,000 men screened and followed for nine years.
The American study, led by Dr. Gerald L. Andriole of Washington
University, had a single design. It found no reduction in deaths from
prostate cancer after most of the men had been followed for 10 years.
Every man has been followed for at least seven years, said Dr. Barnett
Kramer, a study co-author at the National Institutes of Health. By seven
years, the death rate was 13 percent lower for the unscreened group.
The European study saw no benefit of screening in the first seven years of
follow-up.
Screening is not only an issue in prostate cancer. If the European study
is correct, mammography has about the same benefit as the PSA test, said
Dr. Michael B. Barry, a prostate cancer researcher at Massachusetts
General Hospital who wrote an editorial accompanying the papers. But
prostate cancers often are less dangerous than breast cancers, so
screening and subsequent therapy can result in more harm. With
mammography, about 10 women receive a diagnosis and needless treatment for
breast cancer to prevent one death. With both cancers, researchers say
they badly need a way to distinguish tumors that would be deadly without
treatment from those that would not.
When the American and European studies began, in the early 1990s, PSA
testing was well under way in the United States, and many expected that
the screening test would make the prostate cancer death rate plummet by 50
percent or more. Dr. Brawley was at the cancer institute then, though not
directly involved with its prostate cancer screening study. But he saw the
reactions.
Some urologists said the study was unethical, because some people would
not be screened, and demanded it be shut down, he said. One group of black
urologists encouraged black men not to participate because blacks have a
greater risk of prostate cancer and it seemed obvious they should be
screened.
Some thought that they would see fewer cancer deaths among screened men as
quickly as five years. But it became clear that screening would not have a
large, immediate effect ? if it did, the studies would have been stopped
and victory declared. Cancer researchers began turning to less rigorous
sources of data, with some arguing that screening was preventing cancer
deaths and others arguing it was not.
In the United States, many men and their doctors have made up their minds
? most men over age 50 have already been screened, and each year more than
180,000 receive a diagnosis of prostate cancer. In Europe, said Dr. Fritz
H. Schröder of Erasmus University, the lead author of the European study,
most men are not screened. ?The mentality of Europeans is different,? he
said, and screening is not so highly promoted.
Both studies will continue to follow the men. It remains possible that the
United States study will eventually find that screening can reduce the
prostate cancer death rate, researchers say, or that both studies will
conclude that there is no real reduction.
?I certainly think there?s information here that?s food for thought,? Dr.
Brawley said.
The benefits of prostate cancer screening, he said, are ?modest at best
and with a greater downside than any other cancer we screen for.?
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