Adding breast tomosynthesis to traditional mammography increases the detection of the most invasive breast cancers by 41% and reduces the need for reexaminations by 15%, according to a study published this week in JAMA.
Breast tomosynthesis—a 3-D mammogram technology that FDA in 2011 approved for use along with regular 2-D mammograms—takes various X-ray images from different angles to create a three-dimensional image of a patient's breast. The images appear as slices of the breast, so that overlapping tissue cannot obscure the view of tumors.
"It allows us to peel away the layers and see underlying lesions that might be obscured by other tissue," says Sarah Friedewald, lead author of the new JAMA study. She adds, "You can think of regular mammography as showing a closed book. With 3-D you are able to page through the book one page at a time without other information superimposed."
However, it remains unclear whether the new technology is worth its higher price tag. Experts say the technology is too new to know whether it saves lives or misses tumors.
Will 3-D mammograms improve cancer care?
JAMA study: 3-D mammograms may improve detect of deadly cancers
For the study, researchers from the Caldwell Breast Center at Advocate Lutheran General Hospital analyzed data on 454,850 breast exams at 13 academic and community health facilities. Of those exams, 281,187 were conducted with traditional technology and 173,663 were conducted with both traditional technology and 3-D mammography.
With the 3-D mammograms, the clinicians found:
- More invasive cancers. Clinicians in the study detected 4.1 invasive cancers per 1,000 exams using the tomosynthesis, compared with 2.9 per 1,000 exams using digital mammography alone.
- Less need for follow-up. For every 1,000 patients who underwent traditional mammography, 107 were called back for more imaging. With 3-D mammography, the reexamination rate dropped to 91 out of 1,000, a 15% decrease.
In addition, the researchers found that patients who received 3-D mammograms were more likely to get biopsies: 19.3 patients per 1,000 patients who underwent 3-D mammography had biopsies, compared with 18.1 per 1,000 patients who underwent traditional mammography. Nearly 30% of 3-D mammography patients who were biopsied tested positive for cancer, compared with 24% of biopsied patients who underwent traditional mammography.
Debating annual mammograms
The study was funded by the National Cancer Institute and Hologic, the company that manufactures tomosynthesis machines. It is the largest study to date examining the use of the 3-D technology.
Should 3-D mammograms be broadly used?
About 1,100 of the country's 13,500 mammography units use 3-D mammography, according to Hologic spokesperson Jim Culley. This year, an estimated six million U.S. patients will undergo 3-D mammography.
But it is still "uncertain" whether 3-D mammography should be broadly recommended, Etta Pisano—a mammography expert and the dean at the Medical University of South Carolina—writes in an accompanying editorial. Pisano notes that the study was not a randomized clinical trial directly comparing the harms and benefits of the two types of mammograms.
What to consider before you adopt digital breast tomosynthesis
The study is "extremely promising," but clinicians "need to be cautious as we adopt a new technology," Pisano told the New York Times. Pisano says she would not request the technology as a patient.
Moreover, Pisano says her university could not afford a 3-D mammography unit, as it costs about $500,000, or twice the price of a digital mammography machine. And patients sometimes face extra costs because some insurers do not pay for it (Bernstein, Washington Post, 6/24; Grady, New York Times, 6/24; Carroll, NBC News, 6/24; Shute, "Shots," NPR, 6/24; Goldschmidt, CNN, 6/25; Beck, Wall Street Journal, 6/24).
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