Breast cancer screening can be complicated; sometimes it’s more than just a mammogram. For example, when a screening mammogram report says a person has dense breasts, what does that really mean? Why is it important, and what should we do about it?
What does it mean to have dense breasts?
People with “dense breasts” have a higher proportion of glandular tissue and fibrous connective tissue compared to fatty tissue. This can make a screening mammogram more difficult to interpret, because breast tissue, calcifications, and some tumors can all appear white, whereas fatty tissue appears dark. Sensitivity of a mammogram for detecting breast cancer is 86-89% in breasts with mostly fatty tissue, but drops to 62-68% in extremely dense breasts.
Nearly half of all women over the age of 40 who get mammograms have dense breasts, so those are very concerning numbers. Furthermore, as of March 2023, there’s a new FDA regulation that states imaging facilities must notify patients that they have dense breasts. Patients and clinicians alike are left wondering: what are we supposed to do with this information?
How do we screen patients with dense breasts for breast cancer?
In addition to mammograms, there are supplemental breast cancer screening modalities: 3D mammogram (breast tomosynthesis), whole breast ultrasound, breast MRI, and molecular breast imaging. Unfortunately, we don’t have enough research yet to answer the question of what additional testing we should do, or how often.
We may ask ourselves, “Should I be getting an ultrasound for this patient? Maybe a breast MRI?” According to the USPSTF, not necessarily. In May 2023, the U.S. Preventive Services Task Force concluded that “the current evidence is insufficient to assess the balance of benefits and harms of supplemental screening for breast cancer using breast ultrasonography or magnetic resonance imaging (MRI) in women identified to have dense breasts on an otherwise negative screening mammogram.”
A practical approach to determining which imaging modalities to use for your patients is to use the American College of Radiology’s ACR Appropriateness Criteria for Supplemental Breast Cancer Screening Based on Breast Density, which can be found here. When deciding which imaging test to order, the ACR recommends using a combination of the patient’s breast density and their overall risk of breast cancer. Risk may be determined using the Breast Cancer Risk Assessment Tool, which uses personal and family history, demographic factors, and presence or absence of genes associated with breast cancer.
Barriers to breast cancer screening
One important barrier to optimal breast cancer screening is that supplemental screening tests are often not covered by insurance. Women may have to pay more than $1,000 for appropriate screening tests. The Find It Early Act, which would require government and private insurances to cover the sometimes exorbitant costs faced by high-risk women, has been introduced in Congress to try and address this gap.
Some patients would clearly benefit from additional screening beyond mammography. Screening breast MRI has been shown to substantially increase the rate of cancer detection and is recommended in patients who are at high risk (>20% lifetime risk) based on American Cancer Society Guidelines. For patients at “intermediate risk,” such as those with a personal history of breast cancer or a prior biopsy diagnosis of atypia (equivalent to a 15% to 20% lifetime risk), a patient-centered shared decision-making approach is recommended.
Thanks for all you do to help manage breast cancer screenings in your patients. For a deeper dive on breast cancer screenings for patients with dense breasts, how to approach mammography and more, listen to this episode on the Primary Care RAP podcast.