When breast cancer screening uses advanced techniques such as 3D mammograms or synthetic mammograms, fewer women are found to have dense breasts compared to screening with traditional 2D mammography, according to a study.
The research was published online on March 19, 2019, by the journal Radiology. Read “Effect of Mammographic Screening Modality on Breast Density Assessment: Digital Mammography versus Digital Breast Tomosynthesis."
What is breast density and how is it measured?
Dense breasts have less fatty tissue and more non-fatty tissue compared to breasts that aren't dense.
One way to measure breast density is the thickness of tissue on a mammogram. The BI-RADS (Breast Imaging Reporting and Database System), which reports the findings of mammograms, also includes information on breast density. BI-RADS classifies breast density into one of four groups:
- mostly fatty
- scattered areas of density
- consistently dense
- extremely dense
Still, no one method of measuring breast density has been agreed upon by doctors. Breast density is not based on how your breasts feel during your self-exam or your doctor's physical exam. Dense breasts have more gland tissue that makes and drains milk and supportive tissue (also called stroma) that surrounds the gland. Breast density can be inherited, so if your mother has dense breasts, it's likely you will, too.
Research has shown that dense breasts:
- can be twice as likely to develop cancer as nondense breasts
- can make it harder for mammograms to detect breast cancer; breast cancers (which look white like breast gland tissue) are easier to see on a mammogram when they're surrounded by fatty tissue (which looks dark).
Nearly half of women age 40 and older in the United States are classified as having dense breasts.
As of December 2018, more than 70% of states have passed legislation requiring that women be notified of their breast density with mammography results.
What are advanced screening methods?
A traditional mammogram creates a two-dimensional image of the breast from two X-ray images of each breast.
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.
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.
In synthetic mammography, 2D images are created from 3D mammogram information. This means that only one exposure is needed to create both 3D and 2D images, instead of two exposures to capture both 2D and 3D information. This means less radiation exposure for the patient and slightly quicker creation of the final mammogram images.
How the study was done
This study compared the breast density classifications that came from three breast cancer screening methods:
- traditional 2D mammography
- 3D mammography with traditional 2D mammography
- synthetic mammography with traditional 2D mammography
The study looked at 60,766 breast cancer screening results from 24,736 women that were done between Sept. 1, 2010, and Feb. 28, 2017, at the Hospital of the University of Pennsylvania. The women were 40 to 75 years old:
- 42.3% of the women were white
- 57.7% of the women were black
3D mammography with traditional 2D mammography was the most frequently used screening method:
- 8,935 exams were traditional 2D mammography
- 30,779 exams were 3D mammography with traditional 2D mammography
- 21,052 exams were synthetic mammography and traditional 2D mammography
The researchers accounted for age, body mass index (BMI), ethnicity, and the radiologist who read the mammogram, all of which can affect breast density classification.
Overall, the results showed that women who were screened with 3D mammography and 2D mammography were less likely to be classified as having dense breasts compared to women screened with 2D mammography alone.
Compared to 2D mammography alone, a woman’s chances of being classified as having dense breasts were:
- 31% lower with 3D mammography and 2D mammography
- 57% lower with 3D mammography and synthetic mammography
This lower chance of having dense breasts after screening with 3D or synthetic mammography seemed to be more pronounced in women with a higher BMI.
The researchers explained that the lower density classifications may be because 3D and synthetic mammograms display breast tissue in three dimensions, rather than traditional 2D mammograms’ flat display.
“Our findings may have direct implications for personalized screening because breast density assignments, which often drive recommendations for supplemental screening, may vary according to modality, ethnicity, and BMI,” the researchers wrote.
What this means for you
If your mammogram reports consistently say that you don’t have dense breasts or that you do have dense breasts, then that is likely to be accurate. Still, if your breast density varies from mammogram to mammogram, or suddenly changes after you have a mammogram using newer technology, you might want to talk to your doctor or the radiologist who read the mammogram to get a better understanding of your breast density.
If you know that you have dense breasts, there are lifestyle choices you can make to keep your risk of breast cancer as low as it can be, including:
- maintaining a healthy weight
- exercising every day
- limiting or avoiding alcohol
- eating a healthy diet full of fresh, whole foods and avoiding processed foods with a lot of added sugar and salt
- never smoking (or quitting if you do smoke)
- breastfeeding, if you have the option to do so
Along with lifestyle options, many doctors recommend additional screening for women with dense breasts. This might include MRI and ultrasound.
For more information on steps you can take to keep your breast cancer risk as low as it can be if you have dense breasts, visit the Having Dense Breasts page in the Breastcancer.org Lower Your Risk section.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser