Healthy Choices

UC study urges caution on cancer screenings for women with dense breasts

Women with dense breast tissue may not need the additional cancer screenings often recommended by physicians, according to a new study co-authored by a UC Davis researcher.
Women with dense breast tissue may not need the additional cancer screenings often recommended by physicians, according to a new study co-authored by a UC Davis researcher. The Associated Press file

Women with dense breast tissue may not need the additional cancer screenings often recommended by physicians, according to a new study co-authored by a UC Davis researcher.

While well-intentioned, efforts in California and other states requiring that women be informed about their breast density status may be prompting more cancer screenings than are actually necessary, said Diana Miglioretti, a UC Davis biostatistics professor and study co-author. Not all women with this issue need to undergo further screening, she said, and doing so can lead to false positives, burdensome costs and undue stress for some.

“I’ve talked to a lot of women who’ve had a lot of false positive mammograms, and it’s caused a lot of anxiety,” she said. “The main message is really that we might want to focus on breast cancer risk, as well as breast density, when we consider which women could benefit from supplemental imaging.”

Breast cancer advocates have pushed hard in recent years to draw attention to breast density. The condition affects just under half of women, and often signals to physicians a need for additional screening beyond a mammogram. The new study, published May 18 and led by the University of California, San Francisco, suggests that physicians be more selective about additional tests, such as biopsies or ultrasounds.

The study, which surveyed about 365,000 women aged 40 to 74 over a nine-year period, found that more than half of women with heterogeneously or extremely dense breasts – the two more severe categorizations for breast density – were at low to average five-year risk for breast cancer. That means they may not benefit from additional screening.

A woman’s breasts are considered dense if they contain a lot of fibrous or glandular tissue but not much fat. The condition is more prevalent in young women, athletic women and women undergoing hormone treatment for menopause.

On a mammogram, dense breast tissue appears white and foggy and has the potential to mask breast cancer, which also shows up white. That’s especially concerning given that women with dense breasts are also more likely to develop breast cancer.

With those factors in mind, 21 states have passed breast density reporting legislation in the past five years. These laws, including one in California, require that women be informed of their density status and be given the opportunity to ask their physicians about other tests, such as an MRI or a biopsy.

The Breast Cancer Surveillance Consortium, which UCD’s Miglioretti co-leads with other researchers, assesses five-year risk based on a number of factors including age, race, family history, body mass index and prior cancer diagnosis.

Women with high five-year risk and dense breasts would be the most likely to benefit from additional imaging, the study shows. Having dense breasts alone does not always justify additional screening, Miglioretti said.

Joy Melnikow, director of the UC Davis Center for Healthcare Policy and Research, said one of the biggest downsides to additional screening for women with dense breasts is overdiagnosis, or finding cancer that might not be problematic. While cancer policy tends to err on the side of more screening, being specific about who gets screened could help reduce that problem, she said.

“You can find things if you look hard that would never become symptomatic in a person’s lifetime, and if you treat those things, you aren’t helping that person,” Melnikow said. “This is a challenge to the commonly held beliefs around screening practices, so it takes some explaining.”

But for Heidi Wohle, a 37-year-old Sutter patient who has nine female relatives who have had breast cancer, additional screening is key. Wohle’s mother had dense breasts, and her breast cancer was missed on a mammogram. She pushed for additional imaging, and doctors caught her tumor on an ultrasound.

Now Wohle gets some kind of diagnostic screening every six months just to be safe. Wohle worked with the Susan G. Komen foundation while it was advocating for California’s breast density reporting legislation, which took effect in 2013.

“If you have dense breasts alone, some people might feel fine continuing with just mammograms,” she said. “But at least information empowers people to feel like they can have more in-depth conversations with their provider.”

The breast density debate is still a bit of a conundrum, said Dr. Robert Smith, vice president of cancer screening, prevention and early detection for the American Cancer Society. Women with dense breasts are generally at higher risk, and they can have a higher rate of missed cancers. But those statements don’t apply to everyone, and additional tests are costly.

“We need to link the underlying risk with the density, to show for whom the secondary imagery would most benefit,” he said. “The question is: Do we have the resources to do this for people who are concerned?”

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