Women with extremely dense breast tissue have a 4 to 6 times increased risk of developing breast cancer, and their cancers are also less likely to be detected on a mammogram. About 50% of women have dense breasts.
New laws in many US states were recently passed requiring mammogram reports to include information on the density of a woman’s breast tissue. Dense breast tissue is a risk factor for breast cancer and can make detecting breast cancer more difficult with screening mammograms alone. For this reason, more research is underway to determine how to best screen for cancer in women with dense breasts.
So what are “dense breasts”? Breasts consist of fibrous glandular tissue and fat. Dense breasts contain more fibrous tissue and less fat. On a mammogram, dense fibrous tissue has the same white appearance as a breast cancer. This can make it very difficult for radiologists to spot the breast cancer.
A long-standing question is whether or not women with dense breasts should undergo additional imaging screening tests in combination with mammograms. A new study published in the New England Journal of Medicine offers new insight supporting the addition of MRI screening to mammograms for women with extremely dense breast tissue.
The study was conducted in the Netherlands. 40,373 women between the ages of 50 and 75 years with extremely dense breasts and normal screening mammograms were randomized to undergo additional screening via MRI, or receive no additional screening. The study results showed the mammogram plus MRI group experienced 50% fewer interval cancers than the mammogram-only group during a 2-year period (2.5 vs 5 per 1,000 screenings, respectively). The tumors detected on MRI were smaller, of an earlier stage, and more likely to be node-negative than those detected in the mammography-only group.
This study suggests that a combination of mammograms and MRIs can be beneficial for women with extremely dense breast tissue in detecting breast cancer at an earlier stage than mammograms alone. However, it is important to note the results of this study do not suggest adding MRIs will decrease the death rates from breast cancer.
It is important to discuss your screening options with your health care team to see if additional MRI imaging would be beneficial for you based on your specific situation and risk of developing breast cancer.