Does Debate on Breast Density Laws Distract From the Point?

Kate Johnson

February 12, 2015

The best way to screen dense breast tissue for cancer is no clearer after an essay on the subject by three radiologists was published in the February 12 issue of the New England Journal of Medicine.

The trio takes a gentle stand on the unique laws in the United States that require women to be informed if dense breast tissue is detected on mammogram, and call on radiologists to find some clarity on what to do with that information.

The federal Breast Density and Mammography Reporting Act and similar legislation in 21 states provide "an opportunity to strengthen patient–provider relationships by encouraging physicians to engage women in a conversation about the risks and benefits of screening, regardless of breast density," write Priscilla Slanetz, MD, MPH, and her colleagues from Harvard Medical School in Boston.

But the debate over breast density legislation might actually shine the spotlight on the wrong thing, highlighting current confusion rather than focusing on the question of what to do with a diagnosis of dense breast tissue, several experts told Medscape Medical News.

"Discussions of breast density legislation sometimes mask important issues, much as dense parenchyma masks cancers. We can all do better," said Wendie Berg, MD, professor of radiology at the University of Pittsburgh School of Medicine.

"Perhaps, rather than legislating bills mandating that radiologists give information for which we have no good evidence on how to proceed, state legislatures and Congress should push for more funding for national databases and research to answer the many questions surrounding breast density and supplemental screening," said Carol Lee, MD, a diagnostic radiologist from the Memorial Sloan Kettering Cancer Center in New York City who is past president of the Society of Breast Imaging.

Because the risk for breast cancer is higher in women with dense breasts, and because the risk that their cancer will be missed on screening mammography is higher, some breast density notification laws (although not all) mandate that women diagnosed with dense breasts be offered supplemental ultrasound screening.

Widespread adoption of this approach "would be unwise...without careful consideration of the risks and benefits," write Dr Slanetz and her colleagues.

"We are not entirely against supplemental ultrasound screening, but wanted to point out that, at present, there is not much evidence to support it and there may be better tools that could be used to screen women, depending on their risk status," Dr Slanetz told Medscape Medical News.

"While some studies have shown that whole-breast ultrasound screening in addition to mammography in women with dense breasts and above-average risk can detect an additional 3.2 cancers per 1000 women screened, this comes at a substantial cost of false positives, increased patient anxiety, unnecessary biopsies, and increased cost to the healthcare system," she said.

But which tools might be better, and for whom? And do dense breasts even require supplemental screening?

Women with dense breast tissue face a cancer risk 1.2 to 2.1 times higher than women with average breast density, but that risk is still relatively low. "In comparison, the risk of breast cancer is doubled in a woman with a first-degree relative with breast cancer and increased by a factor of eight in a woman known to carry a BRCA1 or BRCA2 mutation, regardless of breast density," the essayists write.

Consider, too, that dense breasts are "normal and common," and are seen in up to 50% of women, they add. In fact, going forward, even more women might be classified as having dense breasts because of a recent change in the radiologic reporting system. "Instead of considering a woman's average breast density, the system will categorize any breast with a dense area as a dense breast. Given the subjective mode of assessment, it's quite possible that the same woman's breasts may be classified as dense one year and not dense the following year," they explain.

With this in mind, "risk stratification" — putting each patient's individual risk in perspective — should guide screening plans, the essayists suggest. "By assessing a woman's individual risk, providers and patients will be better able to tailor the screening regimen to each patient, thereby maximizing cancer detection and minimizing the downsides of screening," said Dr Slanetz. However, she pointed out, none of the available risk-assessment tools incorporate breast density into the risk calculation.

But problems remain. "We do not know which supplemental screening tools are best suited to which women, or whether these additional tests will result in cost-effective benefits or a reduction in mortality," said Dr Lee.

Digital breast tomosynthesis (DBT) "is all the rage now because it is easy to implement and there is a huge 'wow' factor" in its ability to detect subtleties, said Dr Berg. "From the perspective of a woman with cancer not seen on a standard mammogram, however, the added benefit of tomosynthesis is relatively small. Her cancer could still be masked by dense tissue."

The inventor of DBT, Daniel Kopans, MD, a radiologist from Harvard Medical School, tends to agree.

"It remains to be seen how many of the cancers that were missed by conventional mammography and detected by ultrasound will be found by DBT, but as the inventor of DBT, I am fairly certain there will still be cancers that will not be found by DBT," he told Medscape Medical News.

Still, Dr Kopans agrees that the spotlight on supplemental screening is perhaps misplaced when the future of regular screening for breast cancer with mammography is still so precarious.

"Mammography screening is the only test that has been proven to reduce death from breast cancer using the most rigorous scientific method of randomized controlled trials," Dr Kopans told Medscape Medical News. "Unfortunately, groups like the US Preventive Services Task Force want to limit breast cancer screening. As women understandably lobby legislatures and Congress for increasing ways to detect early cancer, ironically, they are in danger of losing access to the one proven technology that is saving thousands of lives," he said. "We need to build on the success of mammography screening by understanding who might benefit from supplemental screening, and develop ways to provide additional screening in a cost-effective fashion."

At the heart of the breast density notification laws is the empowerment of women "to choose to be proactive and seek additional testing to compensate for known limitations of mammography," said Dr Berg.

 
It is about having the potential to reduce the chance of being diagnosed with late-stage disease.
 

"It is about having the potential to reduce the chance of being diagnosed with late-stage disease. We have many tools now that help with that, but information about those tools is often presented in ways that are confusing," Dr Berg explained. "We, as radiologists, are in a position to educate both patients and providers and need to step up to that plate. Many laws require language in our letters to patients recommending they discuss screening options with their physicians, but we have not educated care providers adequately."

This is the one point on which most radiologists, including Dr Slanetz and her coauthors, agree. "It is critical that radiologists work with other specialists and primary care physicians to develop evidence-based recommendations regarding situations in which supplemental screening is advisable and which method is most efficacious," they conclude.

Dr Slanetz and Dr Lee have disclosed no relevant financial relationships. Dr Berg reports receiving compensation for manuscript preparation and data analysis from Supersonic Imagine, and her department receives equipment and research support from GE Healthcare and Hologic and equipment support from Gamma Medica. Dr Kopans reports that Massachusetts General Hospital holds his patent for DBT, which has been licensed to General Electric, from which he will receive 1/16 of the royalties; his research team also receives some support from General Electric.

N Engl J Med. 2015; 372:593-595. Abstract

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