Up to 70,000 American women a year are treated unnecessarily for
breast cancer because they were screened with mammograms, according to
an analysis in today's New England Journal of Medicine that's likely to
reignite a running debate over the value of cancer screening. The
study, whose results are already being challenged by other cancer
experts, finds that nearly one in three breast cancer patients - or 1.3
million women over the past three decades - have been treated for tumors
that, although detectable with mammograms, would never have actually
threatened their lives. The study lays bare perhaps the greatest risk
of cancer screening, called "overdiagnosis," long acknowledged by
doctors and even advocates of mammograms, but unknown to most women who
undergo the procedures.
Overdiagnosis occurs when technology
detects cancers that, although technically malignant, behave as if
they're benign, says study co-author H. Gilbert Welch of The Dartmouth
Institute for Health Policy and Clinical Practice in Lebanon, N.H.
Though it may surprise the average patient, Welch says, doctors have
long known that some tumors aren't actually fatal. Instead, some remain
dormant for years or even disappear on their own.Doctors and public
health campaigns typically emphasize the benefits of mammograms - such
as the potential to detect cancers when they're smaller and more curable
- but ignore the "huge human costs" of women who go through surgery,
radiation and hormonal therapies for nothing, Welch says.
suggested to women that having a mammogram is one of the most important
things you can do for your health, and that's simply not true," Welch
says. "I can't tell you the right thing to do, except to tell women the
truth, tell them both sides of the story. We shouldn't be scaring women.
This is a really close call.
"Though policy experts are familiar
with such tradeoffs, few others understand that, in any screening
program, some women will be harmed while others are helped, says Fran
Visco, president of the National Breast Cancer Coalition. Breast cancer
therapies can be very toxic, leading to second cancers, heart failure
and even death, Visco says. "When you intervene in a healthy
population, you better be sure you're helping them, because you can be
sure you're harming them," says Visco, a breast cancer survivor, who
wasn't involved in the new study.
If it were really clear mammograms saved a lot of lives, there wouldn't be this constant debate."
cancer survivors credit mammograms with saving their lives, a
conviction that can help sustain them through painful treatments.Authors
acknowledge their paper doesn't offer any guidance to women diagnosed
with cancer. Because doctors can't tell for sure which tumors are most
dangerous, they treat all breast cancers - and even pre-cancers - as if
they have the potential to kill, says co-author Archie Bleyer of St.
Charles Health System in Bend, Ore. Cancer advocates had mixed reactions
to the analysis. Some say the authors overestimate the problem of
unnecessary treatment.In a statement, the American Cancer Society says
"overdiagnosis is a matter deserving of attention," but it notes that
other analyses have arrived at different estimates of the number of
patients treated unnecessarily.
Len Lichtenfeld, the society's
deputy chief medical officer, urged people to view the findings "with
caution."Overall, "the benefits of screening mammography outweigh the
risks and harms, which are an unavoidable part of breast cancer
screening," Lichtenfeld says.Rigorously designed clinical trials - the
gold standard of medical evidence - have found that mammograms reduce
the death rate from breast cancer by about 15% in women in their 40s and
50s and 30% for women in their 60s. More recent studies, though less
rigorously designed, suggest the benefits could be even greater, says
radiologist Barbara Monsees, speaking for the American College of
Radiology."We know that overdiagnosis exists," Monsees says.
doctors need better tools to differentiate lethal tumors from
relatively harmless ones, Monsees says, "we should continue to screen,
because we know we can save lives."Authors say their findings suggest
that most of the recent progress against breast cancer has come from
better treatments, rather than early detection.That's because the
greatest reduction in breast cancer mortality has occurred among women
who don't undergo routine screenings, Welch says.
mortality has fallen 42% in patients under age 40, who typically don't
get screening mammograms, but 28% in women over 40, the age at which the
American Cancer Society suggest women begin annual screenings.
Winer, head of breast medical oncology at Boston's Dana-Farber Cancer
Institute, notes that the study found an 8% reduction in the number of
women whose tumors were detected at more advanced stages. Even under a
scenario in which mammograms led more than 1 million women to receive
unnecessary treatment, the screenings would have prevented 410,000
diagnoses of late-stage cancer.
While researchers struggle with
these issues, Winer says, women often hear a much more simplified
message."We probably have to some degree oversold the benefits of
mammography, but we still know that mammography is beneficial, certainly
for women over the age of 50 and likely for some women under 50," Winer
says. "I don't think we need to abandon mammography. It's still our
best test, although we desperately need better tests."
offer different recommendations about the frequency and timing of
mammograms. The American College of Radiology and American Cancer
Society both recommend women get annual mammograms beginning at age 40.
The U.S. Preventive Services Task Force recommends that women be
screened every other year beginning at age 50, but they should make up
their own minds about whether or not to have mammograms before
that.Given the test's limitations, Winer says, women may choose to have
fewer screenings to reduce their risk.
"It certainly suggests
that a woman who chooses to wait until she's 50 to have mammograms, or
who chooses to have mammograms every other year, is making a rational
decision," Winer says.Jackie Fox says she doesn't regret having a
mammogram four years ago, at age 52. Her tumor was very early - often
considered more of a pre-cancer - but doctors said there was a 50%
chance that it could grow into a larger, invasive cancer. "We have to
use the information that we have at the time," says Fox, from Omaha,
Barry Kramer, director of the National Cancer Institute's
division of cancer prevention, says women should be presented with the
full picture of mammography's risks and benefits.
have been instructed that "early detection saves lives," relatively few
are told that screenings also have costs, including the risk of
undergoing surgery, radiation and drug therapy that doesn't help them,
Kramer says. "The risks of overdiagnosis are real," he says, "and women
ought to know about it."