“You have dense breasts,” my doctor said after my last mammogram. This was news to me. I’d had many previous mammograms, but the term dense breasts — meaning breasts that contain more glandular or connective tissue than fatty tissue — had never come up.

I’ve since learned that about 30% of women have dense or extremely dense breasts, and most of them don’t realize it, either. Why breast density matters…

  • Breast cancer risk is higher in dense-breasted women. In fact, a recent study found that breast cancer is about four times more common in women with extremely dense breasts than in women with very low-density breasts.
  • It is harder to screen for cancer in dense breasts because mammogram X-rays do not see through dense tissue as well as they do fat tissue. Radiologist Rachel Brem, MD, director of the Breast Imaging and Interventional Center at the George Washington University Medical Center, told me, “Cancerous tissue and dense areas both appear white on a mammogram, so identifying cancer is like trying to pick out a particular cloud in a cloud-filled sky.” Comparison: Overall, only about 15% of breast cancers are undetectable on a mammogram… but in dense breasts, about one-third of cancers are undetectable.

WHAT’S YOUR DENSITY?

Breast density cannot be determined by touch. It must be assessed visually, with a mammogram or other imaging test. To find out how dense your breasts are, ask the radiologist the next time you have a mammogram. Or ask your primary care doctor, who receives written reports on your mammogram results.

Radiologists rate density on a scale of one to four. A rating of one means the breast contains less than 25% dense tissue… two indicates 25% to 49% dense tissue… three indicates 50% to 74% dense tissue, the range within which breasts are termed “dense”… four means 75% or more dense tissue, also called “extremely dense” breasts.

It is common for density to decrease at menopause. A new Mayo Clinic study suggests that women whose density does decrease have a 28% reduction in breast cancer risk. But: Density may increase after menopause if a woman uses hormone therapy or loses a significant amount of weight. (My own 10-pound weight loss could explain my new dense-breast diagnosis.)

SCREENING TESTS YOU NEED

You can’t do anything to decrease breast density other than to not use hormone therapy — but you can decrease the risk of having cancer go undetected. If you have dense breasts, Dr. Brem recommended…

  • Get an annual mammogram starting at age 40 — and be sure the test is done using the newer digital technology, which provides more accurate results. Digital mammograms are significantly better at revealing cancer in dense breasts than traditional analog technology because they produce images on a computer screen that can be enhanced and magnified for closer viewing. “More than 70% of all mammograms in the US are now done on digital machines, but facilities that do a smaller volume of mammography may not have upgraded yet,” Dr. Brem pointed out. Your doctor can refer you to a radiology facility that provides digital mammograms.
  • Ideally, get your digital mammogram done at a facility that has computer-aided detection (CAD) software. Now widely available, CAD uses a computer to analyze mammogram results and highlight any abnormal areas, alerting the radiologist to check those areas closely. CAD increases mammography’s cancer-detection ability by about 20% — even in women with dense breasts.
  • If you have dense breasts and no other risk factors, you do not need to have an annual breast MRI, Dr. Brem said. But you might want to ask your doctor about getting an annual ultrasound along with your mammogram. “Ultrasound and mammography look at very different characteristics of the breasts and provide different information,” Dr. Brem explained. At present, ultrasound is mainly used in women with unusually dense breast tissue to help determine whether a questionable image on a mammogram is a noncancerous, liquid-filled cyst or a solid mass that might be a cancerous tumor. However, some doctors do recommend routine annual ultrasounds for dense-breasted patients even when there are no other risk factors.

On the horizon: An ongoing study is evaluating 22,000 women using automated whole-breast ultrasound (ABUS). Standard 2D ultrasound uses a handheld transducer that scans the breast section by section, in a piecemeal fashion… whereas ABUS creates 3D images using an automated transducer that consistently and quickly scans the entire breast so no areas are inadvertently missed. Study goal: To determine whether routine screening with ABUS plus mammography is more accurate than mammography alone in detecting cancer in dense-breasted women. “ABUS is an exciting technology — and so far, this approach has definitely detected more cancers than mammography alone,” Dr. Brem said.

To join the clinical trial: Visit www.SomoInsightStudy.org for more information.

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