Breast density laws linked to higher ultrasound use after mammography: Study

More than 40% of American women age 40 and older have dense breast tissue, according to the National Cancer Institute. This type of tissue can make cancer harder to spot on mammograms and is itself associated with a higher risk of cancer. For some, additional screening may be appropriate.

Two kinds of legislation can help drive supplemental imaging for women with dense breasts-notification laws that require that facilities tell women when dense breast tissue is found by a radiologist on a mammogram and insurance mandates that require coverage of the follow-up tests-according to researchers from the Penn State College of Medicine.

In a study of 12.6 million de-identified health records of American women between the ages of 40 and 64 published in JAMA Network Open, the research team found that both forms of legislation independently led to modest increases in follow-up imaging tests like ultrasounds and magnetic resonance imaging (MRIs). However, insurance coverage mandates had nearly four times the impact, associated with roughly 47 additional ultrasounds per 1,000 women screened compared to 13 more from notification laws.

“Notification opens the door for patients to discuss breast density and supplemental screening with their healthcare provider, but it’s not enough if we’re trying to lower barriers for patients,” said senior author Chan Shen, Howard E. Morgan Professor in Surgery and professor of public health sciences at Penn State College of Medicine. “This is the first large nationwide study that examined the influence of notification laws and insurance coverage independently on supplemental imaging whereas prior studies have often mixed these two factors together.”

Breasts are composed of three different types of tissue: fibrous connective tissue, glandular tissue and fatty breast tissue. When someone has dense breasts, they have more fibrous and glandular tissue, which appears white on a mammogram, similar to abnormal changes to breast tissue like a tumor. However, since dense breast tissue can’t be felt during a physical exam and can only be detected on medical imaging, several states have passed legislation to increase awareness of breast density status and the availability of supplemental screening.

“There’s a lot of variation in the legislation,” Shen said. “Some states require that notifications to be sent only to people with dense breasts while others send a general notice to everyone. Some states include information about supplemental screening in the notification letters. A smaller number of states require insurance coverage with some including ultrasound, some including MRI and some including both.”

For example, Pennsylvania passed the breast density notification act in 2013, which requires facilities to inform patients in the Commonwealth of breast density findings. Beginning in 2022, the Commonwealth began requiring all health insurance companies to cover breast ultrasounds and MRIs for women insured in Pennsylvania with high-risk conditions, which includes dense breast tissue.

On the federal level, the Food and Drug Administration began requiring mammography facilities to inform people whether or not they have dense breasts in 2024, but there are no federal laws mandating coverage for supplemental testing.

Working in the national insurance claims database MarketScan, the researchers in this study analyzed the records of women who received routine mammograms between 2008 and 2019 and had continuous insurance coverage for at least six months after the screening. A total of 21% of women lived in states with dense breast notification laws, nearly 60% of whom lived in states that required the notification to include information about supplemental screening tests. A smaller percentage lived in states with insurance coverage laws — 7% lived in states that required coverage for ultrasounds and 3% lived in states that required coverage for MRIs.

The researchers found that telling a woman that she has dense breasts was associated with higher odds of getting a breast ultrasound within six months of a mammogram. When the researchers analyzed data only from states with notification laws, they found that breast ultrasound use was higher when laws required notices to mention supplemental screening and when laws targeted notices specifically to women with dense breasts rather than all women undergoing mammography.

Insurance mandates, on the other hand, had the biggest impact, according to Shen. When states required insurance companies to cover the cost of supplemental imaging, the use of supplemental ultrasounds increased four times more than when states require notification alone.

Notification laws were associated with a small increase in MRI use, about one additional examination per 1,000 women screened. MRI insurance coverage laws, however, were not associated with a statistically significant change in MRI use.

“People with a personal or family history of breast cancer were much more likely to get MRI imaging, which may make uptake of this specific type of imaging less responsive to legislative efforts,” Shen said. “In addition, while we didn’t directly examine cost or logistical factors in this study, MRIs are generally more expensive tests and there are fewer facilities, which may pose accessibility barriers that influence whether someone seeks this type of imaging,”

Despite the modest increases, overall use of supplemental imaging remained low when considering that more than 40% of middle-age and older women have dense breasts, Shen said. Across the study sample, only 9% of women received supplemental ultrasound imaging and 0.6% received supplemental MRI within six months of a screening mammogram. Older women, women living in rural communities and those with other health conditions were all less likely to get follow-up screening.

“Not everyone with dense breasts needs supplemental screening, but you first need to be aware whether or not you have dense breasts to make that decision in consultation with your healthcare provider,” Shen said. “However, the findings suggest that there are logistical and geographical barriers that influence whether or not women seek out follow-up screening like cost, availability of imaging facilities and patient preference. While more research is needed, this study provides some insights on how to maximize the public health impact of dense breast laws.”

Reference:

Kang D, Chetlen A, Zhou S, Wang L, Leslie D, Shen C. Dense Breast Legislation and Supplemental Breast Imaging Among Women Undergoing Mammography. JAMA Netw Open. 2026;9(7):e2626008. doi:10.1001/jamanetworkopen.2026.26008