New FDA guidelines on breast density notifications and implications for overuse

The US Food and Drug Administration (FDA) recently updated their mammography guidelines to require mammography facilities to notify patients about their breast density. This change, which goes into effect September 2024, is a final version of a rule proposed in 2019 (see our previous coverage on this topic).

The FDA guidelines contain suggested language for notifications about breast density:

“Breast tissue can be either dense or not dense. Dense tissue makes it harder to find breast cancer on a mammogram and also raises the risk of developing breast cancer. Your breast
tissue is dense. In some people with dense tissue, other imaging tests in addition to a mammogram may help find cancers. Talk to your healthcare provider about breast density, risks for breast cancer, and your individual situation.”

There are a lot of issues here. Breast density is a risk factor for developing breast cancer, but it is one of many risk factors. There may be women at much higher risk for cancer because of their age, family history, alcohol use, etc. who do not have dense breasts, while others with dense breasts are at an overall lower risk.

While the FDA keeps it simple, saying that “breast tissue can be either dense or not dense,” it’s not actually that clear cut. The American College of Obstetricians and Gynecologists (ACOG) pointed out in a comment to the FDA that “there is no standardized method for assessing breast density,” so whether or not a patient gets a classification of dense breasts depends on the opinion of the radiologist who reads the test. Breast density can also change over time, so one notification may not be true years later.

The notification language also pushes patients toward additional imaging tests by saying they “may help find cancer,” but doesn’t mention that these imaging tests also increase the risk of false positives and other cascade events. There are no trials showing that supplemental cancer screening with MRI or ultrasound improves mortality or morbidity for women with dense breasts.

Previous research on breast density notification policies show a potential for overuse. Studies of state policies notifying patients about breast density show that they strongly increase the likelihood of patients discussing supplemental screening with their doctor, and modestly increase the likelihood of supplemental screening and breast biopsies. If supplemental screening worked as intended and caught dangerous cancers early, one would expect reductions in rates of late-stage cancer in states with these breast density notifications. However, a 2017 study of these policies did not show a difference in rates of regional or metastatic disease between states with and without notifications.

Because of their high false positive rates and lack of proven benefit, ACOG does not recommend routine use of other scans like ultrasound or MRI to screen for breast cancer in women with dense breasts as their only risk factor. The US Preventive Services Task Force, an independent panel that makes evidence-based recommendations about preventive services, concluded that evidence was insufficient to recommend additional screening for women with dense breasts.

This puts doctors in a tough spot, because when patients will come to them seeking information on what to do, they will either have to tell patients to do nothing (which is likely frustrating and unsatisfying for patients) or tell them to get supplemental screening (which is not universally recommended and could put them at harm for cascade events).

“Primary care physicians in states that have passed such laws often feel poorly prepared to counsel women regarding what action to take, if any, for a woman with dense breasts and a normal mammogram.”

Dr. Kenneth Lin, Medscape

There are also significant cost implications of this policy, both on an individual and system level. An estimated 40-50% of women in the US have dense breasts, so if all of them underwent additional supplemental screening, that could have a serious impact on healthcare spending. While screening mammograms are covered under most insurance, additional MRIs can add out-of-pocket costs for patients and biopsies even more.

We know at least one group for whom this guideline change is a win-win: the makers of imaging devices, who have funded groups for years that advocate for breast density notifications.