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Continued Debate Over Mammograms' Value
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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