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CHICAGO, Nov 27 (Reuters) - Controversial U.S. guidelines
for mammography issued in 2009, calling for screening every two
years rather than annually for women over 50 years old, can
result in breast cancers being missed, according to U.S.
researchers studying the hotly debated topic.
This latest study assessing the impact of revised guidelines
issued by the U.S. Preventive Services Task Force three years
ago comes on the back of a chilling analysis published last week
in the New England Journal of Medicine (NEJM).
The NEJM study, using three decades of U.S. government data,
found that nearly one in three patients - or 1.3 million women -
whose cancer was detected through routine mammograms was treated
for a tumor that may not have been life threatening.
Routine screening has traditionally been recommended by the
task force and the American Cancer Society for all women over
the age of 40. The American Cancer Society has not changed its
stance, but the task force issued new guidelines in 2009,
recommending mammography every two years for women 50 to 74
years old.
Dr. Elizabeth Arleo of Weill Medical College of Cornell
University and lead researcher examined the impact of the
revised task force guidelines on women ages 40 to 49, and 65
years and older.
Arleo analyzed data on screening mammography at New York
Presbyterian Hospital/Weill Cornell Medical Center between 2007
and 2010. Over those four years, 43,351 mammograms were
performed, leading to the detection of 205 breast cancers.
Nearly 20 percent of cancers detected with screening mammography
were found in women in their 40s.
"In our book, it seems unacceptable to miss 19 percent of
breast cancers, half of which were invasive," she said, noting
that "invasive" cancers are more advanced because they reside in
the breast tissues and not just the milk ducts, considered to be
the earliest form of breast cancer.
"Our findings favor the American Cancer Society
recommendations. Women over 40 should have annual mammograms. In
my book, there's no confusion. I tell my patients, I tell my
friends and I tell my mother to get annual mammograms," Arleo
said in a telephone interview. "We hope we can quell some of the
confusion."
Arleo pointed out that not one of the 16 members of the U.S.
Preventive Services Task Force is a breast surgeon or breast
imager.
Arleo, who presented her findings at the Radiological
Society of North America meeting in Chicago, dismissed the NEJM
analysis, calling the premise, methods and conclusions of the
analysis flawed.
The NEJM study, she said, is predicated on the theoretical
idea that all women get screened, but in reality, only about
one-third of women over 65 years old actually get screened.
The method is flawed because researchers combined data from
women with breast cancer in the milk ducts with those who had
small invasive cancers, thereby falsely diminishing the results
for late-stage cancers.
And the conclusion is flawed because no one can say for sure
which cancers would have progressed to an advanced or
life-threatening state.
"We need to understand the biology of cancer so we know
which cancers to treat. Until that question is answered,
screening is our best shot," she said.
She acknowledged that false positives are a problem of
widespread screening.
"But for every test, you have to do a risk-benefit analysis,
not just for mammography," Arleo added.
(Reporting by Debra Sherman; Editing by Lisa Shumaker and
Maureen Bavdek)