Oct. 06--As lawmakers around the country rush to enact legislation requiring providers to notify women if their screening mammograms find dense breast tissue, doctors remain at a loss, unsure how to counsel such women.
Dr. Leonard Berlin, professor of radiology at Rush University and the University of Illinois at Chicago, called the array of state laws "a real conundrum. No one knows exactly what to do with them."
According to the advocacy group Are You Dense, 24 states now have laws mandating the reporting of mammographic density, which increases a woman's risk of getting breast cancer and can hide small cancers. Similar legislation is pending at the federal level. The organization has pushed for such state and federal legislation.
Some state laws require that women be informed about the availability of supplemental screening tests, such as ultrasound and magnetic resonance imaging (MRI). While both ultrasound and MRI have been shown to detect cancers missed by mammograms, however, myriad questions remain, among them: Does such additional testing prevent deaths from breast cancer? At what cost? Will insurance cover it?
The problem is widespread, because up to half of all women undergoing routine mammograms have breasts classified as "extremely" or "heterogeneously" dense, meaning they have a high proportion of fibrous or glandular (as opposed to fatty) tissue. It's an especially common problem for women in their 40s, who are more likely to have dense breasts and in whom mammography is notoriously inaccurate.
Researchers have been struggling for 40 years to understand why women with dense breasts have a higher risk of developing breast cancer, but progress has been slow.
"At this point, we can't tell a woman with high density what she can do to reduce her risk," said Rulla Tamimi, a researcher at Harvard Medical School. "All you do is increase her anxiety."
Recently, a study by Dr. Karla Kerlikowske and others at the University of California-San Francisco found that not all women with dense breasts actually are at increased risk -- only those with additional risk factors.
Kerlikowske's team looked at interval cancers, that is, breast cancers that are diagnosed within a year of a normal mammogram. Interval cancers can be especially aggressive, so additional screening tests likely would be most beneficial in women at high risk for such cancers.
The team analyzed more than 800,000 mammograms from 365,426 women. They calculated each woman's five-year risk of developing breast cancer using the Breast Cancer Surveillance Consortium risk model (https://tools.bcsc-scc.org/BC5yearRisk), which factors in age, first-degree relatives with breast cancer, biopsy history, race or ethnicity, and density on the Breast Imaging Reporting and Data System (BI-RADS).
They found a high rate of interval cancers (more than 1 case per 1,000 mammograms) in women with extremely dense breasts if they also had a five-year breast cancer risk of 1.67 percent or greater, and in women with heterogeneously dense breasts if they had a five-year risk of 2.5 percent or higher. That added up to 24 percent of those with dense breasts.
Kerlikowske pointed out that the women in her high-risk group were at risk not only of missed cancers but of advanced cancers. "If you're going to do supplemental screening," she said, "you should target the 24 percent who are really at high risk."
Dr. Edward Sickles, former chief of breast imaging at UCSF, and other radiologists believe the more serious problem of mammographic density is its ability to mask cancers, not its effect on breast cancer risk.
Sickles said the increased risk has been exaggerated by some researchers, who compared women with the densest breasts to those with the fattiest breasts. If, instead, women with dense breasts are compared with average women, the difference is not so great. Even those with extremely dense breasts are only 2.1 times more likely to develop breast cancer, a risk equivalent to having a mother or sister with the disease.
There is great variability in the array of state laws on breast density enacted since 2009. Some just say women with dense breasts should be told they might benefit from additional screening tests. Some, like Connecticut, require doctors to offer ultrasound or MRI. Unlike most states, Connecticut also mandates that insurance cover the additional screening.
According to Are You Dense, Delaware, Louisiana, Michigan and North Dakota passed laws this year. The other states are Alabama, Arizona, California, Delaware, Hawaii, Maryland, Massachusetts, Missouri, Minnesota, Nevada, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, Tennessee, Texas and Virginia.
"Those laws happened before we were ready," Tamimi said. "We don't have clear guidelines or recommendations for these women or their physicians. There's still so much we don't know."
Radiology studies have shown that supplemental imaging with ultrasound can detect some cancers missed by mammography in women with dense breasts. However, a study published this year by Brian Sprague of the University of Vermont Cancer Center concluded that supplemental ultrasonography for these women has little impact on outcome but dramatically increases costs and harms, including false alarms.
Sprague's team looked at ultrasonography because it's widely available and relatively inexpensive. Potential alternatives include MRI and digital breast tomosynthesis, or 3D mammography.
A computer simulation published in the journal Radiology in March found that adding tomosynthesis to biennial mammography would avert 0.5 deaths and 405 false-positive results per 1,000 women. The additional cost per quality-adjusted life year saved was $53,893 with tomosynthesis, compared with $325,000 using ultrasound in the Sprague study.
Dr. Daniel Kopans of Harvard, who invented tomosynthesis, said his test is not meant to be a supplement to regular mammography. Rather, he said, "it will completely replace 2D mammography, just as digital mammography has replaced screen-film mammography. (It's) actually a much better mammogram, since it finds many more early cancers while having fewer recalls."
Like other experts, Kopans stressed that mammography is the only screening test that has been shown in randomized clinical trials, the gold standard of medical evidence, to reduce breast cancer mortality.
But even his "much better mammogram" won't detect every cancer. "Some cancers that are palpable do not show up on mammograms," he said. "All women should be vigilant. If they feel something new, even if it is soon after a (normal) mammogram, they should bring it to their doctor's attention."
Judy Peres is a freelance reporter.
