A study has found that compared to traditional 2D mammograms, 3D mammograms offer fewer false positives and are more effective in women age 65 and older.
The research was published online on April 2, 2019, by the journal Radiology. Read “Digital 2D versus Tomosynthesis Screening Mammography among Women Aged 65 and Older in the United States.”
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 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 older women. The American Cancer Society recommends breast cancer screening should continue as long as a woman with average risk of the disease is in good health and is expected to live 10 more years or longer. Other organizations, including the U.S. Preventive Services Task Force, the American College of Physicians, and the American College of Obstetricians and Gynecologists, say screening isn’t recommended for women age 75 and older or that women can consult with their doctors about whether they should continue breast cancer screening.
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 fueled an ongoing debate 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
Researchers from Massachusetts General Hospital compared screening mammograms from two groups of women:
- 15,019 women with an average age of about 73 years had 2D mammograms from March 2008 to February 2011
- 20,646 women with an average age of about 72 years had 3D mammograms from January 2013 to December 2015
Compared to women who had 2D mammograms, women who had 3D mammograms had fewer false positives. The difference was statistically significant, which means that it was likely due to the difference in screening and not just because of chance.
Researchers use a statistic called “positive predictive value” to evaluate the effectiveness of a screening test. Positive predictive value is the likelihood that a person with a positive test result truly has the disease. The higher the positive predictive value, the more likely the screening test is to accurately identify a person with the disease.
In this study, the positive predictive value of 2D mammography was 11.9%. The positive predictive value of 3D mammography was 14.5%.
“We've shown that screening mammography performs well in older women, with high cancer detection rates and low false-positives, and that tomosynthesis leads to even better performance than conventional 2D mammography,” said study lead author Manisha Bahl, M.D., radiologist at Massachusetts General Hospital and assistant professor of radiology at Harvard Medical School.
She added that the study results do not support a specific age cutoff for mammography screening.
“Guidelines for screening in older women should be based on individual preferences, life expectancy and health status rather than age alone,” Bahl said. “Our research demonstrates that screening mammography and tomosynthesis perform well in older women with regard to cancer detection and false-positives. So, if a woman is healthy and would want her cancer to be treated if it were detected, then she should continue screening.”
What this means for you
3D 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 country offer 3D mammograms.
If you would like to have a 3D mammogram and aren’t sure your facility offers them, 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.
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.
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