We know that breast density is related to the risk of cancer. But now what?

In most states, when a woman gets the results of a mammogram, she also receives, according to law, information on breast density. This is how much a woman's breasts consist of ducts, glands, and connective tissue compared to adipose tissue. And density matters: it's a risk factor for breast cancer and it's harder to detect. In 2009, Connecticut became the first state to pass a law requiring that women who undergo mammograms be informed of breast density – a feature that can only be seen on a mammogram – and nowadays it is important Today, 36 states have similar laws.

It is clear that mammograms are a less effective screening tool for women with dense breasts, but it is unclear what women with dense breasts should do. Current recommendations from the US Preventive Services Task Force indicate that there is not enough information to know if offering them additional screening will help them, and so many women are potentially informed about news without any further information. tried to treat them. In other words, legislators have outstripped scientists, who still do not know how to advise women with dense breasts.

Density is a spectrum, not a binary measure. Radiologists have classified it into four categories, with almost entirely fat breasts at one end and extremely dense breasts at the other. When doctors talk about "dense breasts", they refer to the first two categories, which include about 43% of American women aged 40 to 74 years. This makes it a very common risk factor, affecting tens of millions of women. To complicate matters, density classifications depend on the radiologist's reading and judgments. They are not necessarily consistent over time or between practitioners. And the density can change during the life of a woman; dense breasts are more common in younger women, for example.

A study published in the Journal of Clinical Oncology in 2010 found that these two main density categories were the most strongly associated with cancer in premenopausal women and postmenopausal women using hormone replacement therapy.

Scientists have known for many years that breast density is a risk factor for breast cancer without knowing exactly why. Women, however, were not necessarily part of the conversation. In 2004, Nancy Cappello was diagnosed with stage 3C breast cancer that had spread to the lymph nodes despite a normal mammogram six weeks earlier. She found that she had dense breasts, something she had never heard of before.

Cappello formed a nonprofit organization called Are You Dense ?, which advocated for the adoption of breast density reporting laws currently in effect in most states. Their language and scope vary – some states require only women in the first two categories to be informed of their density; some only mention the potential of density to mask tumors, not to cause more; and some only require general risk information without telling a woman in which category she falls. But the key message is that women should talk to their doctor about their density. Cappello was the lead author of a recent poll published in the Journal of the American College of Radiology, which shows that women overwhelmingly want this information.

But then what do they do with it? "The difficulty with breast density is that there is not a lot of action you can take to change this risk factor," said Christine Gunn, research assistant professor at the Faculty of Medicine at the University of Toronto. Boston, whose areas of research include risk communication and decision making. At this point, the focus of the discussion is focused on providing women with dense breasts with additional screening with imaging tests such as ultrasound, 3D mammograms and MRIs. But there is no consensus on what kind of additional screening is best – or whether one of them will reduce the number of breast cancer deaths.

It is important to note that breast density is associated with an increased risk of diagnostic cancer, but this is not associated with a higher risk of dying Breast cancer – and the prevention of death from disease has always been the gold standard for a screening test. Mammography has not done much to reduce the incidence of metastatic breast cancer, and the frequency with which women should have a mammogram remains a matter of contention. Cappello said it was advantageous to screen for breast cancer at an early stage because advanced cancers have poorer survival outcomes and require more severe and invasive treatments. However, screening also has potential drawbacks: anxiety, false positive results – possibly with unnecessary biopsies – and overdiagnosis in which tumors that would never have been a threat to health are detected and treated. "The more you look, the more you find," said Joann Elmore, a professor of medicine at the David Geffen School of Medicine at the University of California at Los Angeles. And with our current technology and understanding of cancer biology, we can not tell women that one tumor needs to be treated and not another, "said Elmore. So, quite understandably, they are all treated.

If women with dense breasts should be screened or not, depending on who you ask for and how they weigh the benefits and potential risks:

• Current recommendations from the US Preventive Services Working Group indicate that there is not enough information to assess the balance between the benefits and harms of additional screening (with any method) for women with dense breasts and negative mammograms.
• The American Cancer Society says that there is not enough information to say whether women with dense breasts should be screened for additional MRI unless they are already part of a high-risk group.
• The American College of Obstetricians and Gynecologists does not recommend additional tests in women with dense, asymptomatic breasts and no other risk factors.
• The American College of Radiology said this year that women with a personal history of breast cancer and dense breasts should be examined by MRI, and that women with dense breasts but no other risk factors can consider another ultrasound screening after discussing the risks and benefits of their treatment. doctors.

"Everyone agrees that if you track more, you will find other cancers," said Christoph Lee, professor of radiology at the University of Washington. "But with the additional screening, there are benign biopsies and false positives." In addition, the insurance coverage is not uniform, which means that women can pay out of pocket for additional screening that may or may not help, he said.

Women should know their breast density, said Karla Kerlikowske, a professor of medicine, epidemiology and biostatistics at the University of California at San Francisco and lead author of this 2010 risk and density study. breast cancer. But this information needs to be consistent – everyone needs to know, no matter what category they are in. (A woman with a low overall risk and fat breasts can rest more easily knowing that she has an even lower risk of breast cancer.) "If a moral imperative is to give information, it is imperative to give better information, "said Saurabh Jha, a radiologist who has written a lot about screening.

To truly assess a woman's cancer risk, density can not be considered in isolation – it must be discussed with other risk factors, such as family history and previous breast biopsies. The risk calculator of the Breast Cancer Surveillance Consortium can estimate a woman's risk taking all of these factors into account. Breast density is only one part of a woman's overall risk profile, and that's what women really need to know, Kerlikowske said.