A 5-year study has found that compared to traditional 2D mammograms, 3D mammograms find more breast cancers and offer fewer false positives.
The results of this study echo other results suggesting that 3D mammograms are more accurate than 2D mammograms and may help 3D mammography become part of routine breast cancer screening.
The research was published online on March 10, 2020, by the journal Radiology. Read the abstract of “Five Consecutive Years of Screening with Digital Breast Tomosynthesis: Outcomes by Screening Year and Round.”
What is 3D mammography?
Three-dimensional (3D) mammography (also called digital breast tomosynthesis, digital tomosynthesis, or just tomosynthesis) creates a 3D picture of the breast using X-rays. Several images from different angles around the breast are used to create the 3D picture.
A conventional mammogram creates a two-dimensional image of the breast from two X-ray images of each breast.
3D mammography is approved by the U.S. Food and Drug Administration (FDA) and is a standard of care for breast cancer screening. Because 3D mammography is a relatively newer technology, it may not be available at all hospitals and mammogram facilities.
Still, 3D mammography technology seems to have been adopted faster throughout the United States than digital mammography was. According to FDA statistics as of March 1, 2020, of 8,668 certified mammography facilities, 5,989 offer 3D mammograms.
A number of studies have found that 3D mammograms find more cancers than traditional 2D mammograms and also reduce the number of false positives.
A false positive is when a mammogram shows an abnormal area that looks like a cancer but turns out to be normal. Ultimately, the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.
The mammogram debate
The rate of false positives has helped fuel an ongoing debate about the value of screening mammograms. Doctors who question the value of mammograms say that while mammograms do save lives, for each breast cancer death prevented, three to four women are overdiagnosed. Overdiagnosis means either:
- a screening mammogram finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
- a screening mammogram finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated
Studies on the benefits and possible harms of screening mammograms and the resulting stories in the media have raised controversy about the value of mammograms.
Many radiologists believe that 3D mammograms are better for breast cancer screening and that 3D mammograms may help ease concerns about the value of mammograms. This is why many studies are comparing 3D mammograms to traditional 2D mammograms.
How this study was done
The researchers analyzed the results of 67,350 screening mammograms that were done in 29,310 women between September 2011 to September 2016:
- 56,839 were 3D mammograms
- 10,511 were 2D mammograms
On average, the women in the study were about 56 years old.
Rates of women who were called back for more imaging because something looked suspicious on a screening exam were:
- 8.0% for women who had a 3D mammogram
- 10.4% for women who had a 2D mammogram
This difference was statistically significant, which means that it was likely due to the difference in screening method and not just because of chance.
Breast cancer detection rates were:
- 6 per 1,000 women screened with 3D mammography
- 5.1 per 1,000 women screened with 2D mammography
While this difference favors 3D mammograms, it was not statistically significant.
The researchers noted that nearly 33% of the cancers found by 3D mammograms were considered to have a poorer prognosis, compared to 25% of the cancers found by 2D mammograms.
"We showed that the improved performance with [3D mammography] was maintained over multiple years," said Emily Conant, M.D., professor and chief of breast imaging in the Department of Radiology, Perelman School of Medicine at the University of Pennsylvania. "This is the longest follow-up with cancer registry matching that has been published thus far."
Conant is the lead author of the study and a member of the Breastcancer.org Professional Advisory Board.
"With [3D mammography] you can remove some of the overlapping or obscuring breast tissue so that both normal and abnormal findings are better seen," she continued. "That provides both improved cancer detection and decreased false positives."
What this means for you
If you would like to have a 3D mammogram and aren’t sure your facility offers it, call and check before you make your appointment. If the facility doesn’t offer 3D mammograms, ask your doctor to recommend a facility that does.
To learn more about 3D mammography, including how it’s done and how it’s different from 2D mammography, visit the Breastcancer.org Digital Tomosynthesis page.
Written by: Jamie DePolo, senior editor