Breast cancers found with 3D mammography were more likely to be smaller and node-negative (meaning they had not spread to the lymph nodes) compared to breast cancers found with standard digital mammography, according to a study.
The research was published online on Feb. 28, 2019, by the journal JAMA Oncology. Read the abstract of "Association of Digital Breast Tomosynthesis vs Digital Mammography With Cancer Detection and Recall Rates by Age and Breast Density."
What is 3D mammography?
Three-dimensional mammography (also called digital breast tomosynthesis, 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 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), but isn’t yet considered the standard of care for breast cancer screening. Because it’s a newer technology, it may not be available at all hospitals and mammogram facilities.
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 the ongoing debate about the value of screening mammograms, especially for women younger than 50. In October 2015, the American Cancer Society recommended that women at average risk of breast cancer start annual screening mammograms at age 45 (instead of 40).
“The issue for women ages 40 to 49 is that with conventional 2D mammography there are clearly too many false positives,” said Emily Conant, M.D., chief of breast imaging and professor of radiology at the University of Pennsylvania Medical Center and member of the Breastcancer.org Professional Advisory Board. “At the same time, we can't even find some of the cancers on 2D mammography. Many of the false positives in this age group are because the mammogram is their first, or ‘baseline,’ with no earlier mammograms to compare it to so the radiologist can say, ‘Oh, that is the way her breasts have always been — this is just normal for her.’”
Conant was one of the authors of a 2016 study that found the benefits of 3D mammograms last over time. “The findings reaffirmed that 3D mammography is a better mammogram for breast cancer screening,” she said.
Conant is the lead author of the study reviewed here.
How the study was done and results
The study compared the results of 3D mammograms and conventional 2D digital mammograms done on 96,269 women age40 to 74. The women had the screening mammograms between 2011 and 2014.
- 129,369 were conventional 2D digital mammograms
- 50,971 were 3D mammograms
The average age of women who had conventional 2D digital mammograms was 56.4 years. The average age of women who had 3D mammograms was 54.6 years.
Overall, the study found that screening with 3D mammography increased breast cancer detection rates by about 40%.
Also, 3D mammography found smaller invasive cancers that were more likely to be node-negative and HER2-negative compared to conventional 2D digital mammography:
- 73.7% of breast cancers found with 3D mammography were 1 centimeter (cm) or smaller and node-negative
- 65.4% of breast cancers found with digital mammography were 1 cm or smaller and node-negative
This difference in detecting small breast cancers was especially notable in women age 40 to 49. For these women, 3D mammography found 4.41 invasive cancers per 1,000 exams in women with nondense breasts compared to 2.71 invasive cancers per 1,000 exams found by conventional 2D digital mammography.
Screening with 3D mammography seemed to find breast cancers at an earlier, more treatable stage in these younger women. For women age 40 to 49:
- 25% of breast cancers detected with 3D mammography were considered to have a poor prognosis
- 40.4% of breast cancers detected with conventional 2D digital mammography were considered to have a poor prognosis
Screening with 3D mammography also reduced recall rates — the number of times women had to schedule follow-up appointments because of a suspicious area on a mammogram that turned out to be normal. Recall rates were 40% lower with 3D mammography compared to conventional 2D digital mammography.
“Our results support the evolving literature showing that screening with [3D mammography] simultaneously improves breast cancer detection while reducing false-positive recalls,” Conant and her colleagues wrote. “Although these smaller cancers may not have transformed into more aggressive subtypes, they are expected to be associated with better long-term prognosis.”
What this means for you
Three-dimensional mammography technology seems to be being adopted faster throughout the United States than conventional 2D digital mammography was. According to 2018 statistics from the FDA, about 4,000 facilities out of 8,726 certified mammography facilities in the county offer 3D mammograms.
The results of this study offer more evidence that 3D mammograms find more cancers than traditional 2D mammograms, especially for younger women, and may help 3D mammography become part of routine breast cancer screening.
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
Reviewed by: Brian Wojciechowski, M.D., medical adviser