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 final 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.
The STORM (Screening with Tomosynthesis or Standard Mammography) study found that adding a three-dimensional view to a conventional two-dimensional mammogram found more cancer and decreased the number of false positives.
A false positive is an abnormal area that looks like a cancer, but turns out to be normal. Besides worrying about being diagnosed with breast cancer, a false positive means more tests and follow-up visits, which can be stressful.
The study was published online on April 25, 2013 by The Lancet Oncology. Read the abstract of “Integration of 3D digital mammography with tomosynthesis for population breast-cancer screening (STORM): A prospective comparison study.”
More than 7,290 Italian women ages 48 and older participated in the study. The women had never been diagnosed with breast cancer and didn’t have any symptoms. The women had both a two-dimensional and a three-dimensional mammogram done, one right after the other. The 3-D mammogram was merged with the 2-D mammogram to create a more complete view of the breast.
The researchers then read the mammograms in two phases. They read the two-dimensional mammograms first and then read the integrated 2-D and 3-D mammogram. Two radiologists looked at each mammogram because double reading has been shown to be more accurate than having only one radiologist read a mammogram. After either reading, the radiologists could decide whether a woman needed to be called back for more testing because of a suspicious area.
Of the 59 cancers found in 57 of the women:
- 39 were found by both mammograms
- 20 were found only by the integrated 2-D and 3-D mammogram
So the integrated 2-D and 3-D mammograms found 8.1 cancers per 1,000 screens compared to 5.3 cancers per 1,000 screens for the 2-D mammograms.
Of the 395 false positives:
- 181 came from both mammograms
- 141 came only from 2-D mammograms
- 73 came only from integrated 2-D and 3-D mammograms
The researchers estimated that requiring a positive result on an integrated 2-D and 3-D mammogram before calling a woman back for more testing could have reduced the false positive rate by 17.2% without missing any cancers.
These results are very promising and support earlier studies suggesting the benefits of combining 3-D mammography/digital tomosynthesis with digital mammography.
Still, 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 two-dimensional mammogram.