Keeping Cancer in
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To screen or not to screen?
The mammography debate rages on, newly fueled by results from a
Canadian trial published in the Sept. 3, 2002, Annals of Internal
The Canadian National Breast Screening Study (CNBSS) is the first
trial designed specifically to assess screening mammography in women
ages 40–49. In the early 1980s, the CNBSS recruited 50,430
women in this age group with no history of breast cancer. Half were
assigned to receive annual mammograms; the other half, to receive “usual
care,” meaning that mammograms were done only if a patient’s
doctor recommended them.
After an average of 13 years, there were 105 breast cancer deaths
in the mammography group and 108 in the usual care group — not
statistically significant difference. The researchers concluded that
mammograms are not justified for breast cancer screening in women
under age 50.
Critics of the CNBSS trial said the data came from older technology,
before improved imaging was available. The women who took part enrolled
20 years ago, when mammography images were less clear and radiologists
weren’t as proficient at reading them.
But the American Cancer Society, the Centers for Disease Control
and Prevention, and the National Cancer Institute advise women to
get annual mammograms starting at age 40.
To further muddy the waters, the same issue of Annals of Internal
Medicine that carried the CNBSS results published new guidelines
for breast cancer screening from the U.S. Preventive Services Task
Force (USPSTF). The USPSTF is a panel of health experts that analyzes
published research and makes suggestions about preventive health
The group recommends having a mammogram every one to two years,
starting at age 40. The authors assert that there is no convincing
evidence to support the theory that starting annual screening at
age 40 exposes women to undue harm, with minimal chances of finding
On the other hand, if mammograms can find breast cancer, why not
start at age 40? For one, the screening test may adversely affect
some women. False-positive results (which flag a problem when none
exists) can lead to anxiety and further testing.
In defense of its recommendations, however, the USPSTF says that
anxiety usually disintegrates after cancer is ruled out. And even
when it doesn’t go away, anxiety doesn’t seem to discourage
women from continuing their screening regimen.
If you have a family history of breast cancer or other risk factors,
it makes sense to start mammograms at age 40 (perhaps earlier, depending
upon your level of risk). For everyone else, a discussion with your
doctor is the most sensible first step. If she or he feels annual
mammograms are unnecessary for you, and you’re comfortable
with the decision, waiting until you’re 50 should be fine.
November 2002 Update
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