Women with Dense Breasts and Additional Screenings

Normal Dense Breast Tissue
Normal Dense Breast Tissue on a Mammogram. National Cancer Institute

A new study, supported by the National Cancer Institute (NCI), found that women, with dense breasts, can benefit from a screening strategy that is not limited to following up a negative mammogram with additional screenings such as an ultrasound, a PET scan or an MRI. The study suggests that  the best predictor of a woman developing a breast cancer after having a negative mammogram, and before her next mammogram, is a screening strategy that also takes into account other risk factors such as age, race, family history and history of breast cancer biopsies.

Breasts have a mixture of fibrous and glandular tissue and fatty tissue. Your breasts are considered dense if you don’t have much fat, and your breasts have a lot of fibrous or glandular tissue. The only way you would know your breast density is if you had a mammogram. Only a radiologist can determine your breast density. You can’t feel it. Firm breasts don’t mean dense breasts.  

There are four categories used to describe breast density:

  1. Breasts that are the least dense have almost all fatty tissue
  2. Breasts that have scattered areas of fibroglandular density
  3. Breasts with heterogeneous density
  4. Breasts that have almost all glandular and fibrous tissue with little to no fatty tissue.

Dense breasts can make finding a cancer more difficult on a mammogram. Yet, mammograms are still considered to be the screening tool of choice for those women who have dense breasts. Whenever possible, a woman with dense breasts should have a digital mammogram as digital has proven to be a more effective screening tool than the traditional film mammogram.

Dense breasts show up on mammograms as white, and, as such can hide a tumor, since cancer also shows up as white. So additional tests are given to rule out any cancer not picked up in a mammogram.

Dense breasts are not uncommon. About half of the women having mammograms have dense breasts. Dense breasts are more common in younger women, and women who take hormone therapy to relieve signs and symptoms of menopause.

Dense breasts are considered an increased risk for breast cancer.  High breast density often causes false-negative findings on a screening mammography.

Concern over the increased risk for breast cancer in women with dense breasts has resulted in 22 states having legislation that mandates doctors to inform women if they have dense breasts, and to discuss having additional imaging such as MRI, PET, or ultrasound following a normal mammogram. Congress is currently considering enacting similar legislation.

While additional imaging can find breast cancers that are missed in a mammography, these imaging procedures may result in increased numbers false-positive results.  False positives necessitate having more procedures, which include the pain and anxiety of unnecessary biopsies.

The study, led by Karla Kerlikowske, M.D., of the University of California, San Francisco, was published in the Annals of Internal Medicine.

Data used in the study came from 365,000 women ages 40 to 74 years in the Breast Cancer Surveillance Consortium (BCSC), an NCI funded program.

A five-year breast cancer risk for each woman took into consideration breast density, age, race, any family history of breast cancer, and her history of breast biopsies to estimate breast cancer risk over the next 5 years.

Researchers found that about 47 percent of the women had dense breasts. Those women at highest risk of getting a cancer between mammograms were those having 75 percent of their breast tissue considered dense tissue.

The BCSC risk calculator is designed as a tool to assist clinical decision-making. Primary care providers can calculate a 5-year breast cancer risk using the risk calculator and use this information in their discussions about supplemental or alternative screening methods in women with dense breasts. The risk calculator can also be used to compare one woman’s risk relative to the average risk for a woman of the same age and ethnicity.

"This study is a good example of using information wisely to personalize risk estimation,” said Stephen Taplin, M.D., M.P.H., of NCI’s Division of Cancer Control and Population Sciences.

Based on the study’s results, Dr. Kerlikowske said, “It just doesn’t make sense for all women with dense breasts to get additional screening.”

Sources: The National Cancer Institute, and the Annals of Internal Medicine

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