Three-dimensional mammography (also called digital tomosynthesis or just tomosynthesis) creates a three-dimensional picture of the breast using X-rays. Several low-dose images from different angles around the breast are used to create the 3-D picture.
A conventional mammogram creates a two-dimensional image of the breast from two X-ray images of each breast.
Three-dimensional mammography is approved by the U.S. Food and Drug Administration, but isn’t yet considered the standard of care for breast cancer screening. Because it’s relatively new, it’s not available at all hospitals and mammogram facilities.
A Swedish study adds more evidence to research suggesting that 3-D mammograms find more cancers than traditional 2-D mammograms.
The study was published online on May 1, 2015 by the journal European Radiology. Read “Performance of one-view breast tomosynthesis as a stand-alone breast cancer screening modality: results from the Malmö Breast Tomosynthesis Screening Trial, a population-based study.”
The Malmö Breast Tomosynthesis Screening Trial plans to enroll 15,000 Swedish women ages 40 to 74. All women in Sweden are included in the country’s breast cancer screening program. Sweden has a national health system so healthcare tends to be the same throughout the country. A national health system also makes it easier to track health outcomes.
This study is an analysis of the first 7,500 women in the study.
When the women went in for their regular mammograms, they got both a 3-D mammogram and a conventional 2-D mammogram. Each image was read by two different very experienced radiologists.
Breast cancer was detected in 68 women. Of these cancers:
- 46 were found by both 3-D mammogram and 2-D mammogram
- 21 were found by only 3-D mammogram
- 1 was found by only 2-D mammogram
This means that 3-D mammography found about 40% more breast cancers than conventional 2-D mammography.
Women may be called back for more tests if an area on a mammogram looks like cancer but turns out to be normal. This is called a false positive. Besides worrying about being diagnosed with breast cancer, a false positive means more tests and follow-up visits, which can be stressful.
In this study, the recall rates were:
- 3.8% for 3-D mammography
- 2.6% for 2-D mammography
This means that 3-D mammography had more false positives than 2-D mammography. Still, both of these recall rates are very low. In other studies recall rates have been 10% or higher.
The overall positive predictive value -- the percentage of mammograms with positive results that led to a cancer diagnosis -- was 24% for both 3-D and 2-D mammograms.
While these results are very exciting, more research needs to be done before 3-D mammography becomes part of routine breast cancer screening. Because it is another imaging test, 3-D mammography exposes women to additional radiation. Researchers are looking at ways to replace a standard mammogram image with one created from 3-D mammography images while reducing radiation exposure.
Visit the Breastcancer.org Digital Tomosynthesis page to learn more about how 3-D mammography is done and how it’s different from a 2-D mammogram.
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