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Wednesday, April 20, 2011
By Daniel B. Kopans, MD
Mammography screening is one of the most important advances in women's health in the past 50 years. Since annual screening began, the death rate from breast cancer has decreased by more than 30 percent.
Prior to 1990 the death rate from breast cancer had been unchanged for more than 50 years. Mammography screening began, at a national level, in the mid 1980s, and soon after, the death rate began to drop. Since 1990, the death rate has decreased by more than 30 percent.
Although advances in therapy have been important, studies in the Netherlands and Sweden show that most of the decline in deaths has been due to earlier detection afforded by mammography screening. Therapy only saves lives when cancers are found early.
Unfortunately, this undeniable success continues to be clouded by misinformation arising from inappropriate data analyses. Such confusion can do real harm if it dissuades woman from availing themselves of annual screening mammography.
A controversy that erupted last year over whether screening should begin at age 40 or 50 is one example (see the sidebar, "Screening mammography facts"). More recently, a "viral" email claiming a connection between mammography and rising thyroid cancer rates has alarmed many women.
A recent episode of The Dr. Oz Show focusing on this issue pointed out (correctly) that the incidence of thyroid cancers has been increasing among women over the past 30 years.
The host of the show, Mehmet Oz, MD, attributed radiation exposures during dental x-rays and mammograms as possibly contributing to this increase. This was unfortunate since there is absolutely no evidence that mammograms have anything to do with the increase in thyroid cancers.
Here are the facts:
The bottom line: There is no risk to the thyroid during a mammogram, and a shield can actually compromise optimal imaging. Shields are available for patients who insist on having them. But women must be aware that using one not only confers no benefit in terms of thyroid cancer prevention, but may in fact compromise the mammogram and its lifesaving benefits.
Daniel B. Kopans is a Senior Radiologist in the Breast Imaging Division at Massachusetts General Hospital Imaging and Professor of Radiology at Harvard Medical School.
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