When it comes to breast cancer risk, you’ve probably heard about family history and genetics. But have you heard about breast density?
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If you haven’t paid attention to density in the past, start now. In one recent study, 47 percent of women between the ages of 40 and 74 had what we call “mammographically dense” breast tissue.
Here’s why that matters: Dense breast tissue can make tumors more difficult to spot in mammograms. And extremely dense tissue may be an independent risk factor for developing breast cancer.
How do you know your density?
“When you do have a mammogram, be sure to ask for your density. Then remember it. Along with factors such as family history and your genetics, it’s an important fact to know and understand.”
Holly Pederson, MD
This may come as a surprise, but you can’t determine density based on how your breasts feel. They may feel firm or lumpy to you but still not show up as dense tissue on a mammogram. Or they may feel soft to you but still show up as dense in images.
When you have a mammogram, it includes a scale for breast density. Women who fit two different categories — heterogeneously dense or extremely dense — fit the general definition of having dense breast tissue. That’s the definition used in the study above.
Density changes with age and weight. We expect a fit woman in her mid-30s to have dense breasts, for example. But density decreases in later decades, and being overweight or obese is associated with less dense tissue.
Because dense breasts limit the sensitivity of screening mammography, at least 21 state governments require doctors to notify women if they have dense breasts after a mammogram. And a similar bill was introduced in the U.S. Senate earlier this year.
Beyond the mammogram
In the study mentioned above, the breast cancer risk was highest for women who had dense breasts and other risk factors for cancer. The study included risk factors such as first-degree relatives with a history of breast cancer, a personal history of breast biopsy, and race or ethnicity.
The study is a good start, because we haven’t had good models for understanding how density fits into risk assessment. But there’s more work to be done. Future studies should focus on more risk factors and exactly which women will benefit most from supplemental imaging —the tests that go beyond a mammogram.
Perhaps you’ve heard of the “3-D mammogram,” for example. This technique, called CT tomosynthesis, enhances the sensitivity of testing and can spot cancer in dense breasts more accurately than traditional mammograms. Its use also decreases the call-back rate for women who have screening mammograms, a common source of anxiety.
There’s also whole-breast ultrasound, which may increase detection by as many as 4.2 cases per 1,000 women with dense breasts. And MRI screening is the most sensitive technique of all, with about 95 to 98 percent sensitivity, compared with about 81 to 87 percent for mammograms. With all of these techniques, there’s a question of whether they’re universally available — and covered by insurance. And MRIs are used only in high-risk cases.
In the coming years, expect more research on these techniques and more guidance on when and how we should use them. For women with dense breasts, they can be valuable tools for detecting cancer early, when treatment is most effective.
What you can do
Cleveland Clinic’s approach to mammograms recommends yearly screening for most women starting at age 40.
When you do have a mammogram, be sure to ask for your density. Then remember it. Along with factors such as family history and your genetics, it’s an important fact to know and understand.
If, for example, you’re a woman with a family risk of breast cancer and dense breasts, your doctor may recommend more specialized screening. But even if you don’t have genetic risk factors but do have dense breasts, a discussion of risk and risk modification with your doctor is always worthwhile.
Guidelines do vary — and there’s a lot of debate about them. The more you know about any and all risks you have personally, the better you can participate in conversations about your present and future health.