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The addition of 3-D mammography to conventional digital mammography substantially improved detection of invasive breast cancers and reduced the number of women called back for reexamination, according to the first large study of the new technology, released Tuesday.
Doctors in 13 academic and community health settings discovered 41 percent more of the most lethal cancers when women had both traditional digital mammograms and the 3-D screening known as "tomosynthesis." The technology, approved by the Food and Drug Administration in 2011, provides images that appear as slices of the breast, removing the effect of overlapping breast tissue that can obscure views of tumors.
Sarah Friedewald, co-medical director of the Caldwell Breast Center at Advocate Lutheran General Hospital in Park Ridge, Ill., who led the study, unequivocally endorsed the value of 3-D mammography over conventional imaging. "In my opinion," she said of any woman about to be screened for breast cancer, "she should have the 3-D mammogram."
The paper, published online in the Journal of the American Medical Association, reviewed 454,850 examinations from 13 sites across the country -- 281,187 conducted with digital mammography and 173,663 that provided the traditional mammogram and tomosynthesis. The improved technology found 41 percent more invasive cancers (4.1 per thousand women screened versus 2.9 per thousand); and more cancers overall (5.4 per thousand versus 4.2).
The addition of tomosynthesis also reduced the need to recall women for further testing from 107 per thousand to 91 per thousand, which decreases patients' anxiety and holds down health care costs. There was no difference in discovery of ductal carcinoma in situ, a condition that is the subject of heated debate concerning overdiagnosis and overtreatment of some breast cancers.
The 3-D screening subjects women to more radiation than traditional mammography, but the amount is still well within limits set by the FDA, Friedewald said. However, it costs more, is not available everywhere and is not always covered by insurance, she said.
"It's hard to justify purchasing more equipment when it's not guaranteed to be paid for," she said.
Breast cancer kills 40,000 women annually, according to the American Cancer Society, although screening mammography has been important in reducing the mortality rate. But in recent years, women have been subjected to a confusing outpouring of information and research on who should be screened for breast cancer, when and how often. In July, a committee of the National Cancer Institute warned of overdiagnosis and overtreatment of some cancers, suggesting a name change for ductal carcinoma in situ, which is not invasive and, the committee said, should not be labeled a cancer. In recent years, influential medical boards in the United States, Canada and Switzerland have revised their recommendations on screening mammography as debate continued over false positive findings and overdiagnosis.
In an editorial that accompanied the 3-D mammography study Tuesday, two physicians who were not involved in the research suggested that the results will renew debate, this time over whether tomosynthesis should replace digital mammography, the way that technology replaced X-ray film. They called for more study.
Previous studies have reached similar conclusions as Tuesday's paper about the value of 3-D mammography, but all were from single sites and so of limited value. The research released Tuesday was retrospective and so was not correlated with patient outcomes, an area that Friedewald said needs additional study.