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Should
you have that Mammogram? Let
those biostatisticians slug it out down at the National Cancer Institute
- I’m getting my yearly mammograms anyway.
Then again, the way things are going, should I? Last
week, the latest panel of experts took a crack at sorting out the
decades-old mess about mammograms: Do these X-rays really save lives? Or
do they just make us feel like we’re doing something, no matter how
mystical, to reduce the
risk of dying from breast cancer? The
panel, called the P.D.Q. screening and prevention editorial board, is an
independent group of specialists convened by the cancer institute. Its
job is to sort out complicated data – the mammogram debate surely fits
the bill - and put it up on NCI’s web site (www.cancer.gov).
Its
specific mission was to review controversial assertions published last
fall as a letter in the British journal Lancet by Danish researchers,
Ole Olson and Peter C. Goetzsche, who looked at data from the seven key
mammography studies. The
Danes concluded, and last week the P.D.Q. panel concurred, that there is
insufficient evidence to prove that mammograms prevent deaths from
breast cancer, according to Donald A. Berry, a panel member and chair of
the biostatistics department at M.D. Anderson Cancer Center in Houston. Among
the flaws? Assessment of cause of death may not have been done in a
“blinded” way in some research, that is, without knowing whether a
woman was in the screening group or not. Some researchers did not
exclude women with pre-existing cancer at equal rates in mammogram and
control groups and other “egregious “mistakes, says Berry. According to the Danish researchers,
two of the seven studies were so flawed as to be completely useless - the New York and Edinburgh studies, both of which found a
benefit to mammography. Three other studies
- the Two-County
Study in Sweden, the Stockholm study and the Goteborg study, all of which found a benefit to mammography – were deemed
of poor quality. So far, that’s five studies, all
showing a benefit, all deemed unreliable. The
two studies that the Danes thought were done properly were the Malmo
study and the Canadian study. The Malmo study found a slight benefit to
mammography. One part of the Canadian study found no benefit at all, and
the part that focused on younger women found more
deaths in the screening group, though this could have been due to
chance. Needless
to say, the P.D.Q. panel’s interpretation of the Danes’
interpretation of the seven key studies is not universally accepted. Dr.
Daniel B. Kopans, director of the breast imaging division at
Massachusetts General Hospital and a staunch advocate of mammography
calls the Danish analysis and P.D.Q.’s acceptance of it “ a
travesty…It’s a mistake to use the nonscience from the Danish study
to dissuade women from potentially life-saving screening.” The
five studies the Danes rejected were actually “among the best done,”
says Kopans, and the Canadian study, which the Danes applauded, was
poorly done. “These guys don’t know what they’re talking about.” This
morass is both big news and same old, same old. It’s
big news because invasive breast cancer is estimated to have hit 192,000
women last year to have killed 40,200. It’s also important because
women have fought hard to get mammograms covered by insurance and
because many women believe (or have been led to believe) that if they
just get mammograms, they’ll either be magically protected against
breast cancer, or at least will have a better shot at surviving it if we
do. (The first is obviously untrue, the second is what’s up for
grabs.) Among
the continuing believers in mammography are the American Cancer Society
and, with more ambivalence, the National Cancer Institute. Dr.
Robert C. Young, president of the American Cancer Society, stresses that
the death rate from breast cancer has been declining in recent years.
(It’s not clear, however, whether this is due to wider use of
mammography or more aggressive treatments.)
“With
widespread use of mammography,” he argues, the presence of cancer in
lymph nodes at the time of initial surgery “has gone from 60 percent
in the 1980s to less than 30 percent in the 1990s. And the size of
breast cancer lesions on average has gone from 3 centimeters in the
1980s to 2 centimeters now.” Furthermore,
he says, the real benefit of mammography may not be seen for
another 15 to 20 years. Dr.
Peter Greenwald, director of cancer prevention at the National Cancer
Institute, acknowledges that the institute’s recommendations “have
not been totally consistent.” But he is sticking by current NCI
recommendations: a mammogram every one to two years for women, starting
in their 40s, and starting
earlier, for women at high risk whose doctors recommend it. But
this whole mess smacks of same old, same old, too. The seven studies now
at issue are the same seven studies that researchers have been fighting
about for years, particularly with regard to younger women. At
a consensus conference called by NCI in January, 1997, that panel of
experts concluded that women in their 40s should make up their own minds
about mammography because the survival benefit to younger women is so
small. That
turned out to be a politically incorrect decision. The American Cancer
Society disagreed vehemently. In February, the National Cancer Advisory
Board, which oversees the NCI, got into the act. Then Congress, which
oversees the NCI’s budget, weighed in, making it clear that if the NCI did not recommend mammograms for younger women, its budget
could be cut, recalls Berry. Surprise,
surprise, the NCI then reversed itself, recommending mammograms for
younger women. All
of this might be considered academic squabbling were it not for one
thing. Many women dutifully
have mammograms in part because they take
a “Why not? It can’t hurt” attitude. But
mammography can hurt (and not
just the compression during the X-ray). One outcome of mammography can
be more testing, some of it painful, most of it, anxiety provoking. The
good news is that most suspicious mammograms turn out to be false
alarms, but to be sure of this, women put themselves through biopsies
and other tests. Mammograms
aren’t exactly foolproof in the other direction, either. In younger
women, mammograms miss 25 percent of cancers; in women 50 and over,
mammograms miss 15 percent of cancers. That’s bad, too, obviously, because women may delay
treatment. Women’s
health advocates have long held a more nuanced view of mammography than
lay women, arguing that while mammograms may detect breast cancer
earlier than clinical (manual) exams, this is not really early
detection, merely earlier. The latest
mess “confirms what many of us have suspected,” says Fran Visco,
president of the Washington,D.C.-based National Breast Cancer Coalition.
“The evidence behind screening mammography is poor, certainly for
women under 50. For too long, we feel, mammography has taken up too much
space in the world of breast cancer…we need to look more at how to
prevent the disease, how to detect it early, at access to quality care
for all women.…those are the big issues.” “Mammography
is not the answer to the breast cancer epidemic,” the coalition added
in a prepared statement last week. “ In any age group, mortality
reduction associated with mammography is less than 50
percent….Although it may be difficult to accept, it is vital that
women know the truth about breast cancer screening and the false sense
of security it provides.” Cindy
Pearson, executive director of the Washington, D.C.-based National
Women’s Health Network, agrees. “It’s better that we know this and
are confused than we are kept in the dark like in the old days. So,
ladies, where does this leave us? Among other things, in the same boat
as men, who are often urged to have PSA testing for prostate cancer
without understanding that this test may lead to more and more invasive
interventions, some of which may be damaging or of little survival
value. As
for mammograms, the P.D.Q. panel is writing up its conclusions now and
expects to finalize them in March. At that point, the NCI may or may not
decide to alter its current recommendations. None
of this uncertainty is going to go away. It would probably help if
everybody (the media included), obsessed a bit less about breast cancer,
terrifying though it can be, and a bit more about statistically greater
threats, like heart disease, for which there is ample evidence that
improvements in exercise and diet can reduce risk. Ultimately,
the answer is not an endless series of expert panels endlessly
re-hashing old data on an obviously imperfect test. The real answer is
genuine prevention and cures that work. Meanwhile,
I’m keeping that mammogram appointment.
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