Combining breast density information with a woman’s 5-year breast cancer risk estimate can help doctors figure out which women are at high risk for the disease and should therefore have additional screening beyond yearly mammograms, according to a study.
The research was published online on July 1, 2019, by the journal JAMA Internal Medicine. Read the abstract of “Strategies to Identify Women at High Risk of Advanced Breast Cancer During Routine Screening for Discussion of Supplemental Imaging.”
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 the breast 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.
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.
Proposed U.S. legislation would require doctors to discuss supplemental breast cancer screening with women who have dense breasts. Still, other research has shown that not all women with dense breasts have a higher risk of breast cancer. So these women with dense breasts at average risk of breast cancer would not need additional screening. The purpose of this study was to better identify women with dense breasts at high-risk of breast cancer who would benefit the most from additional screening.
How 5-year breast cancer risk was estimated
To estimate the 5-year risk of breast cancer for each woman in the study, the researchers used the Breast Cancer Surveillance Consortium Risk Calculator.
The Breast Cancer Surveillance Consortium is a collaborative network of breast imaging registries doing research to assess and improve the delivery and quality of breast cancer screening in the United States. The Breast Cancer Surveillance Consortium Risk Calculator is an interactive tool designed by researchers that participate in the Breast Cancer Surveillance Consortium to estimate a woman’s 5-year risk of developing invasive breast cancer. The calculator was designed to be used by healthcare professionals. If a woman uses the tool and she is not a healthcare professional, the consortium encourages her to discuss the results with her doctor.
How the study was done
To do the study, the researchers looked at the medical histories of 638,856 women ages 40 to 74 who had screening mammograms done at a Breast Cancer Surveillance Consortium imaging facility from Jan. 3, 2005, to Dec. 31, 2014.
The researchers used BI-RADS classifications to determine each woman’s breast density. As mentioned above, the Breast Cancer Surveillance Consortium Risk Calculator was used to determine each woman’s 5-year risk of developing invasive breast cancer.
Overall, 47% of the women in the study had consistently dense or extremely dense breasts.
The researchers then looked to see how many women were diagnosed with stage IIB or higher breast cancer within 1 year of a screening mammogram.
The researchers found that 60% of the stage IIB or higher breast cancers were diagnosed in women with dense breasts.
Overall, 12.5% of the women had dense breasts and a high risk of breast cancer. High rates of stage IIB or higher breast cancer were diagnosed in women with a:
- 5-year breast cancer risk score of 2.5% or higher and consistently dense breasts (6% of the women)
- 5-year breast cancer risk score of 1.0% or higher and extremely dense breasts (6.5% of the women)
"Studies consistently report that women can experience anxiety and concern in response to breast density notification, and most practitioners are not prepared to counsel women about breast density and are uncertain about offering supplemental imaging," the researchers wrote. "Our findings provide important information to guide women and practitioners about when supplemental imaging may be most beneficial and when it would not."
The researchers also said that 5-year breast cancer risk should be calculated every 3 to 5 years to ensure that women at high risk of the disease are identified.
What this means for you
If you learn that you have dense breasts and are unsure what that means, contact a member of your healthcare team to learn how your breast density affects your personal risk of breast cancer. While you’re talking about your breast density, you may want to bring up this study and ask your doctor to calculate your 5-year risk of invasive breast cancer. If you do have a higher-than-average risk of breast cancer, talk to your doctor about additional screening, including MRI and ultrasound.
There are also 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
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 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