This transcript has been edited for clarity.
Today, I’m going to talk about the 2023 Food and Drug Administration regulation that requires breast density to be reported on all mammogram results nationwide, and for that report to go to both clinicians and patients. Previously this was the rule in some states, but not in others. This is important because 40%-50% of women have dense breasts. I’m going to discuss what that means for you, and for our patients.
First
Breast density describes the appearance of the breast on mammography. Appearance varies on the basis of breast tissue composition, with fibroglandular tissue being more dense than fatty tissue. Breast density is important because it relates to both the risk for cancer and the ability of mammography to detect cancer.
Breast density is defined and classified according to the American College of Radiology’s BI-RADS four-category scale. Categories 1 and 2 refer to breast tissue that is not dense, accounting for about 50% of the population. Categories 3 and 4 describe heterogeneously dense and extremely dense breast tissue, which occur in approximately 40% and 50% of women, respectively. When speaking about dense breast tissue readings on mammography, we are referring to categories 3 and 4.
Women with dense breast tissue have an increased risk of developing breast cancer and are less likely to have early breast cancer detected on mammography.
Let’s go over the details by category:
For women in categories 1 and 2 (considered not dense breast tissue), the sensitivity of mammography for detecting early breast cancer is 80%-90%. In categories 3 and 4, the sensitivity of mammography drops to 60%-70%.
Compared with women with average breast density, the risk of developing breast cancer is 20% higher in women with BI-RADS category 3 breasts, and more than twice as high (relative risk, 2.1) in those with BI-RADS category 4 breasts. Thus, the risk of developing breast cancer is higher, but the sensitivity of the test is lower.
The clinical question is, what should we do about this? For women who have a normal mammogram with dense breasts, should follow-up testing be done, and if so, what test? The main follow-up testing options are either ultrasound or MRI, usually ultrasound. Additional testing will detect additional cancers that were not picked up on the initial mammogram and will also lead to additional biopsies for false-positive tests from the additional testing.
An American College of Gynecology and Obstetrics practice advisory nicely summarizes the evidence and clarifies that this decision is made in the context of a lack of published evidence demonstrating improved outcomes, specifically no reduction in breast cancer mortality, with supplemental testing. The official ACOG stance is that they “do not recommend routine use of alternative or adjunctive tests to screening mammography in women with dense breasts who are asymptomatic and have no additional risk factors.”
This is an area where it is important to understand the data. We are all going to be getting test results back that indicate level of breast density, and those test results will also be sent to our patients, so we are going to be asked about this by interested patients. Should this be something that we talk to patients about, utilizing shared decision-making to decide about whether follow-up testing is necessary in women with dense breasts? That is something each clinician will need to decide, and knowing the data is a critically important step in that decision.
Neil Skolnik, MD, is a professor, department of family medicine, at Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, and associate director, department of family medicine, Abington (Pennsylvania) Jefferson Health.
A version of this article first appeared on Medscape.com.