'Dense Breast' Proposal Would Lead to Unnecessary Worry and Tests

Marcia Frellick

May 16, 2019

Requiring all women and their referring physicians to receive a summary of breast density after each mammogram, as recently proposed by the US Food and Drug Administration (FDA), may have broad and costly unintended consequences.

Such a breast density report may needlessly worry and confuse many millions of women and lead to unnecessary imaging and added costs without clear benefit, warn two experts.

Nancy L. Keating, MD, MPH, and Lydia E. Pace, MD, MPH, both internists at Brigham and Women's Hospital, Boston, Massachusetts, discuss the issues in an essay published online May 9 in JAMA.

The FDA proposal was published in the Federal Register in March and is open for public comment until June 26. It suggests that every woman who has a mammogram and her referring provider receive a follow-up summary about breast density. The letter would include an explanation that dense breasts may make cancer more difficult to spot on a mammogram and that additional imaging may be needed.

Women would be told whether they have dense breasts — meaning the mammogram shows they have more fibrous and glandular tissue than fatty tissue — and whether the density is high or low. About 43% of women ages 40 to 74 have dense breasts (heterogeneously dense or extremely dense).

Some women are already receiving density notification letters. The federal proposal followed the implementation of notification laws in 37 states.

In its impact statement, the FDA says the benefit would be fewer breast cancer deaths from catching cancer earlier after density notifications. The impact statement also says detecting cancer earlier will save the healthcare system money.

However, Keating and Pace write that these statements "have no basis in evidence."

State-level mandates have led to modest increases in additional imaging, primarily in ultrasound and breast biopsies, they point out.

But there's no evidence, the authors say, that having additional imaging tests, such as ultrasound, MRI, or 3D mammograms, will save lives.

"There are no data to suggest that supplemental imaging for women with dense breasts improves cancer outcomes, including mortality, and such imaging is associated with false-positive results, unnecessary biopsies, and presumably overdiagnosis," Keating and Pace write.

They note that in 2016, the United States Preventive Services Task Force concluded that there wasn't enough evidence to recommend for or against additional breast imaging for women who have dense breasts.

The authors give an example of the uncertainty of benefit compared with mammography in hand-held or automated whole-breast ultrasound, which they write "detects an additional 4.4 cancers per 1000 examinations." In 14% of cases, the article states, supplemental ultrasound results are found to be suspicious and require follow-up diagnostic imaging or biopsy (recall rate). The probability that someone with a positive screening with supplemental ultrasound will actually have breast cancer (positive predictive value) is 3% to 8%.

The test that may be most helpful, Keating says in an accompanying JAMA audio author interview, is 3D digital breast tomosynthesis (DBT), which can increase identification of tumors compared with mammography (5.8 vs 4.5/1000 examinations). At the same time, it would decrease recall rates (127 vs 109/1000 examinations) in the United States, "where we have traditionally had very high recall rates," she comments.

Some Costs Left Out of FDA Estimate

As for costs, the authors say that although the FDA included in its estimates costs associated with more imaging, the agency did not include costs for inevitable overdiagnosis and treatment or additional visits to primary care providers for counseling.

Keating and Pace spell out two other major concerns for the proposed new rules.

One is that readings of the images are variable, whether read by the same radiologist or different radiologists. The authors note that variation can change the determination from dense to nondense in 13% to 19% of women over 2 to 3 years. So the same women would be told she has dense breasts after one screening, but nondense breasts after another, which would cause unnecessary worry and lack of confidence in screening, the pair comment.

Another is that the notification language must be understandable to women at all literacy levels and, thus far, the language in the state notifications that are already being sent out has not scored well in that regard, they comment.

"Even with optimal language, patients will need additional counseling by primary care clinicians," Keating and Pace add.

What Clinicians Can Do

The FDA's proposal would affect a number of medical specialties, including radiology, primary care, oncology, and public health.

It presents an opportunity for clinicians to talk with their patients about breast density and individual risk based on factors beyond breast density, Keating and Pace suggest.

However, they also suggest that "discussions about the potential benefit of supplemental imaging should be limited to women at high risk of breast cancer based on other risk factors."

Clinicians may also want to discuss the option of annual screening rather than every 2 years, in particular for women at higher risk of breast cancer.

Discussing lifestyle modifications to lower cancer risk is also important, the authors write, including limiting alcohol, striving for a healthy weight, and exercising regularly.

Amy Abernethy, MD, PhD, the FDA's principal deputy commissioner, said in a statement that "helping to ensure patient access to information about the impact that breast density and other factors can have on the risk for developing breast cancer is an important part of a comprehensive breast health strategy."

However, Keating argues in the author interview that "while this seems like the right thing to do, it's not deeply seeded in evidence yet. Notification is going to be part of our future, and I think our next challenge, then, is to really continue the research that will gather evidence about long-term outcomes."

JAMA. Published online May 9, 2019. Editorial

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