Breast density laws ensure that women receive critical breast-health information, supporters say, but many of the laws broadly classify breast density and fail to account for varying levels of risk.
Research shows that the sensitivity of mammography is reduced by up to 20% in women with dense breasts and that breast density is the strongest predictor of the failure of mammograms to predict breast cancer. This occurs because dense breasts-those containing a higher ratio of fibroglandular tissue to fat-can obscure or mask a cancer (Figure).
The phenomena of masking prompted initial legislation in Connecticut mandating that breast density be reported to both patients and providers. To date, 12 states have passed breast density laws (Table). In short, this legislation requires facilities to notify women with dense breasts in writing, alerting them that the condition can interfere with the effectiveness of a screening mammogram. These notifications may also give patients advice about discussing screening options with their primary physician and report that dense breast tissue may be an independent risk factor for breast cancer.
Some believe that this legislation ensures that all women who undergo a mammogram will receive critical breast-health information. But there is a downside, according to the California Breast Density Information Group (CBDIG), a group of breast radiologists and breast cancer risk specialists representing academic and community-based practices in California.
Many of the laws broadly classify breast density and don’t account for the varying levels of risk among patients with different breast densities. The CBDIG explains: When risk is expressed relative to average breast density, the risk for the 40% of women with heterogeneously dense breasts is about 1.2 times greater than average and the risk for the 10% of women with extremely dense breasts is about 2.1 times greater than average. Therefore, breast density is a risk factor, but not a strong one.
Another problem is that the Breast Imaging-Reporting and Data System (BI-RADS) composition classification system is quite subjective. Breasts in category 1 are considered the fattiest, whereas breasts categorized as 4 are the densest. Category 1 and category 4 breasts may be easy to classify, but breast tissue in the middle categories may sometimes be classified as “2” and at other times “3” depending on the day, according to observational studies.
The implications of these laws are significant, since approximately 50% of women undergoing screening mammography have either “heterogeneously dense” or “extremely dense” breasts. “For California alone, this could mean 2 million notification letters a year, and a significant increase in supplementary screening with MRI and ultrasound,” the CBDIG stated.
Supplemental screening for every woman with dense breasts would result in very substantial additional costs to the health care system, explained CBDIG member Jafi A. Lipson, MD, assistant professor of radiology at Stanford University School of Medicine. “There also is concern that the increased use of supplementary screening will ultimately expose some patients to more harm, in the form of false-positive results, than good.”
“Increased patient awareness may be considered a benefit, although there are also potential harms of notification, including awareness without a clear path forward for women and care providers, increased unsubstantiated anxiety, potential for misunderstanding or overestimation of density-associated risk and increased propensity to over-screen,” said Lipson.
To help physicians navigate patient concerns about breast density findings, the CBDIG has created a management flow chart.
An individualized risk-based approach should guide decision-making. Women at high risk for breast cancer, such as those who are BRCA-positive, are more likely to benefit from additional screening with MRI or ultrasound or tomosynthesis (“3D mammography,” a promising supplemental screening technology). For women at intermediate risk for breast cancer, the decision to have supplemental screening should be made on a case-by-case basis using a shared decision-making approach.
“The benefits of additional screening are diminished for women who are not high risk, while the potential harms remain the same,” the CBDIG said.
For some women, the addition of a single screening ultrasound to mammogram increases detection of breast cancers that are small and node-negative. However, only Connecticut has an insurance mandate for supplementary screening, so for many women, supplementary screening may be an out-of-pocket cost.
In addition, there currently are no specific billing codes for screening breast ultrasound or tomosynthesis, although this likely will soon change. And to further complicate the process: every commercial payer has its own policies about whether they will cover these services.
Lipson JA, Hargreaves J, Price ER, for the California Breast Density Information Group (CBDIG). CBDIG Web Site. Available at: http://www.breastdensity.info/. Accessed September 20, 2013.