By Melissa Healy, Los Angeles Times
Screening women for breast cancer using traditional digital mammography plus a technique that yields a three-dimensional picture of the breast improves detection of cancer and reduces the number of women called back unnecessarily for further tests and biopsies, a new study has found.
The addition of tomosynthesis, a technique not widely available before 2011, to digital mammography increased the numbers of cancers found in women screened from 0.42 percent to 0.54 percent — a 29 percent increase. The latest research, published Tuesday in JAMA, did not follow women for years to discern whether tomosynthesis saved more lives. But recent research has suggested that tomography is likely better at detecting the most deadly cancers—small invasive cancers and lobular cancers—than digital mammography alone.
While tests that increase detection rates often come at the cost of increasing false positives, the latest study found that adding the 3D pictures to routine mammography actually had the opposite effect: 10.5 percent of women who got mammograms alone were called back for additional imaging or biopsy; but among those being screened with mammography plus tomosynthesis, only 8.9 percent had to endure the anxiety, expense and risk of being called back for further tests.
While digital mammography takes a single, static picture of the breast, tomosynthesis passes a low-dose X-ray source in an arc across the breast, creating a series of images. Computer software then lines the images up to create a three-dimensional image of the breast. Smaller cancerous lesions are less likely to be obscured behind dense tissue or other structures within the breast, and a radiologist can glean a better picture of the size and shape of an abnormality, reducing confusion over whether it has malignant potential.
“We now have a better mammogram,” said the study’s lead author, Dr. Sarah M. Friedewald, a diagnostic radiologist at Advocate Lutheran Hospital in Libertyville, Ill. While several studies have suggested there might be a benefit in adding a third dimension to breast cancer scans, Friedewald said that the current research does so with greater clarity. This study’s robust findings emerged from the collected records of 13 breast imaging centers across the United States, which conducted nearly 455,000 breast-cancer screenings between 2010 and 2012.
Friedewald noted that insurance companies now reimburse unevenly for the more expensive screening that uses both digital mammography and tomosynthesis. “We’re hoping this will shed light on and increase awareness” of the benefits of the enhanced scanning technique, Friedewald added, “so they’ll be more consistent.”
In an editorial accompanying the JAMA study, a pair of experts in radiological diagnosis acknowledged that the new study is unlikely to end the recurring debate over the value of breast cancer screening.
Those inclined to believe that breast-cancer screening saves lives will be cheered by the availability of a technique that makes detection better without driving up false-positive results, wrote Dr. Etta D. Pisano of the Medical University of South Carolina and Martin J. Yaffe, a researcher at the University of Toronto’s Ontario Institute for Cancer Research.
But those who question the value of yearly screens for all women after 40 or 50 will cite the current study’s absence of follow-up, which might reveal whether better or earlier detection of cancers allowed more women to live, and for longer, they added.
Paul Falardeau via Flickr
