Three-dimensional mammography (also called digital 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 study has found that 3-D mammography found more breast cancers and led to fewer call backs compared to conventional 2-D mammography.
The study, “Implementing Digital Breast Tomosynthesis in a Screening Population,” was presented on Dec. 4, 2013 at the Radiological Society of North America Annual Meeting.
The study was led and presented by Breastcancer.org Professional Advisory Board member Emily Conant, M.D., chief of breast imaging at the University of Pennsylvania Medical Center.
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 researchers compared mammogram results from 15,633 women who had a 3-D mammogram to results from 10,753 women who had a conventional 2-D digital mammogram. Six radiologists who were trained to read 3-D mammograms reviewed the images.
The average recall rates were:
- 8.78% for 3-D mammograms
- 10.40% for 2-D digital mammograms
This means that 3-D mammograms had 15.6% fewer false positives than 2-D digital mammograms.
The cancer detection rates were:
- 5.24 per 1,000 women for 3-D mammograms
- 4.28 per 1,000 women for 2-D digital mammograms
This means that 3-D mammograms found 22% more cancers than 2-D digital mammograms.
The overall positive predictive value -- the percentage of mammograms with positive results that led to a cancer diagnosis -- was 4.1% with 2-D mammograms and 6.0% with 3-D mammograms, a 46% increase. Specifically, 3-D mammograms found 30.1% more invasive breast cancers than 2-D mammograms.
In March 2013, the STORM study also found that 3-D mammography led to better detection rates and fewer false positives. This new study echoes those results.
“It’s the most exciting improvement to mammography that I have seen in my career, even more important than the conversion from film-screen mammography to digital mammography,” said Dr. Conant. “The coming years will be very exciting, as we see further improvements in this innovative technology.”
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.