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By Gina Kolata
A new study in a British medical journal
has stirred a passionate debate among doctors in Europe and
the United States by asserting that mammograms do not prevent
women from dying of breast cancer or help them avoid mastectomies.
The question is dividing experts and women's
health advocates, many of whom acknowledge that they do not
know what to think about the new report. For more than two
decades, annual mammograms have been part of life for millions
of women, with the American Cancer Society and the National
Cancer Institute urging women to have them.
Experts are still digesting the new
findings, which appeared in the Oct. 20 issue of the journal
The Lancet.
Women have long been urged to have the
test every year starting at age 50 or sooner, and promised
that early detection will reduce their chances of dying from
breast cancer by about 30 percent. And detecting cancer early,
they were told, would allow women to avoid extensive surgery
and harsh treatments that might be needed to control a larger
tumor found later.
But the new analysis, of seven large studies
of mammography conducted over the past few decades, says those
promises are an illusion. It calls into question
the assumption that early identification of breast tumors,
before they can be felt in an external examination, improves
the chances of a cure.
Those studies
that found benefits from mammography were flawed,
say the investigators, Dr. Peter Gotzsche, director of the
Nordic Cochrane Center in Copenhagen, and Ole Olsen, the deputy
director. Recent studies, more rigorously designed and conducted,
found no such effects, they assert.
For example, they criticize a New York
study from more than a quarter of a century ago finding that
women who never had a mammogram died of breast cancer at a
rate 30 percent higher than those who had the test.
Dr. Gotzsche and Mr. Olsen say this study,
and four others, do not meet agreed-upon standards for well-conducted
and reliable research. They question whether the subjects
who had mammograms might have been substantially healthier
than those who did not, and whether deaths among women who
had mammograms might be less likely to be ascribed to breast
cancer than deaths among women who did not have them.
"The quality of the trials was very
surprising because it is pretty low," Dr. Gotzsche said
in a telephone interview. "Even if they are judged by
yesterday's standards, the quality is low. In some cases,
we know why that happened - these trials were conducted by
people who were unfamiliar with clinical trial methodology.
They were run by enthusiastic clinicians."
The researchers cite with greater approval
a more recent study in Malmo, Sweden, that compared 21,088
women who had mammograms to 21,195 who served as controls.
After nearly nine years, 63 women in the mammogram group had
died of breast cancer, compared with 66 in the control group
- an insignificant difference.
The other study the researchers approved
of, done in Canada, involved 44,925 women who had mammograms
and 44,910 who did not. There were 120 deaths from breast
cancer in the screened group and 111 among the women who served
as controls.
Nor did mammography
lead to fewer mastectomies, the investigators say.
In the Malmo study, for example, 424
women in the mammography group and just 339 in the control
group had mastectomies.
One reason may be that doctors aggressively
treated some tiny tumors found in mammograms - tumors that
might never have developed into cancer or might never have
been noticed in a woman's lifetime.
So far, just one country, Switzerland,
has taken action as a result of the study, deciding not to
offer a national mammography screening program. Dr. Gianfranco
Domenighetti of the Swiss Network for Health Technology Assessment
said the decision was heavily influenced by the Danish research.
But Switzerland did not have a national
program; it was thinking of starting one. It is a different
matter in a country like the United States, which has a longstanding
policy of urging women to have mammograms.
Once a program
has been highly promoted and advanced as a way to save lives,
said Dr. Barnett Kramer, the associate director for disease
prevention at the National Institutes of Health, it
can be difficult to suggest that guidelines be revised.
Nevertheless, some American experts, including
researchers at the National Institutes of Health, say that
the analysis deserves consideration, and that women
should at least be aware of the debate.
The debate has nothing to do with the
effectiveness of breast cancer treatment. There is agreement
that treatment, with surgery, hormones and chemotherapy, saves
lives. Instead, the question - which has come up before with
screening tests for other kinds of cancer - is whether earlier
treatment is better.
At its heart, the analysis challenges
the assumption that the period when a tumor can be seen on
a mammogram but not felt in a breast examination is a critical
period in which cure is possible. If that assumption is wrong
- if cancers can be just as treatable, or just as deadly,
whether they are found early or late - then mammography would
offer no benefits.
A similar problem recently emerged with
breast self-examination, another method of early detection
that had been highly promoted. When studies in China and Russia
indicated that it did not prevent breast cancer deaths, the
cancer institute quietly dropped its emphasis on the method,
saying in a database primarily for doctors that there was
insufficient evidence of its value.
The institute will ask a panel of independent
experts that advises it on that same database to look at the
new mammography study, said Dr. Peter Greenwald, the institute's
director for cancer prevention.
Dr. Greenwald added that there might be
a simple explanation for the discrepancy among the studies
analyzed by the researchers in Copenhagen. Newer treatments
are saving women's lives, he said.
That may mean that a woman's prognosis
is nearly the same whether tumors are found early, with mammography,
or later, when they can be felt. If this is the case, earlier
mammography studies, conducted when treatments were less effective,
would have found that screening prevents breast cancer deaths;
more recent studies might not have found this effect.
But the most important question, Dr. Gotzsche
said, is not whether women are saved from dying of breast
cancer; it is whether mammograms prolong their lives. It is
possible, he said, that a mammogram might find a cancer early,
leading to treatment that might prevent a breast cancer death.
But theoretically,
the treatment might be so harsh that it precipitates another
illness, so that the woman lives no longer, although
her death is not attributed to breast cancer.
No one study was large enough to answer
that question, so the investigators combined study data. They
concluded that the overall death rate did not budge when women
had mammograms compared with when they did not.
But some doctors who want to advise their
patients confess that they are whipsawed by the dueling experts.
"The debate has become so sophisticated
from a methodology viewpoint that as a doctor my head is spinning,"
said Dr. Barron H. Lerner, an internist and historian at Columbia
University's College of Physicians and Surgeons. Dr. Lerner
wrote "Breast Cancer Wars" (Oxford University Press,
2001).
"You read the article in The Lancet
and you nod your head yes. Then you read the studies by people
on the other side and you nod your head yes," Dr. Lerner
said. "We're witnessing this fight between the pro- and
anti-mammography forces and they're both arguing that `my
data is better and we're right and they're wrong.' "
What should be done, Dr. Lerner said,
is "sitting back and trying to analyze how we as patients,
as doctors, as a society, should deal with these conflicting
data."
That is an issue that is plaguing some
advocacy groups.
The report "is really causing a huge
amount of concern among activists," said Cindy Pearson,
the executive director of the National Women's Health Network.
She said her group no longer advocates self- examination.
Now, she said, if mammograms are not useful, "you're
just left out there with nothing."
Fran Visco, president of the National
Breast Cancer Coalition, said she welcomed the mammography
dispute. "We know that mammography screening has serious
limitations, yet it has been sold as the be-all and end-all
for breast cancer," Ms. Visco said. "When someone
says, `We have to question that assumption,' we're thrilled.
We've been questioning it from the beginning."
"I'm not ready to tell women over
50 not to get screened," Ms. Visco said. "But what
we are telling women is that we don't have a good screening
test to detect breast cancer early and we're not sure what
to do when we find it early."
It is time,
she said, to focus on these issues rather
than assume that mammograms are the answer.
Abstracted
from The New York Times December 9, 2001
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