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FAQ For High Risk Women & Women With Dense Breast Tissue


50% of women have dense breasts. Conventional digital mammography may not detect an early cancer in dense breasts. Women with dense breasts should consider adjunctive imaging to increase the likelihood of detecting a cancer when it is small. 3D mammography (tomosynthesis) is the adjunctive imaging test of choice in the vast majority of cases. In women who are considered high risk for developing breast cancer, breast MRI in addition to mammography is recommended.

What is breast density?

There are two main types of breast tissue that make up the breast: fatty tissue and glandular tissue. Fatty tissue is dark on the mammogram. Glandular tissue is white or grey on the mammogram. Breast density is subjectively determined by the radiologist’s “eyeball” estimate of the percentage of glandular tissue with respect to the fatty tissue on the screening mammogram. If there is an equal or greater amount of glandular tissue in the breast compared to the fatty tissue, this is considered “dense breast tissue” (Illustration A). Approximately 50% of the female population is considered to have dense breast tissue. If you read your mammogram report, the breast density category should be stated. The two categories that qualify as dense breast tissue are “heterogeneously dense” and “extremely dense”.

Dense breast tissue categorized by a screening mammogram does NOT correlate with breast firmness as determined by physical exam.

PBSS Illustration

Why should women be aware of their breast density status?

First, the more glandular tissue in the breast (white on the mammogram), the higher chance a developing cancer (also white on the image) may be obscured, or masked, by the glandular tissue. Studies have shown that radiologists may not see 15-20% of cancers on a 2D digital screening mammogram. The more glandular tissue present in the breast, the more difficult it may be for the radiologist to see the cancer. Because of this, additional breast cancer screening tests may be warranted in women with dense breast tissue. In most cases a 3D mammogram is considered satisfactory for breast cancer screening in women with dense breast tissue.

However in high risk patients (see below) breast MRI is recommended in addition to screening mammography (2D or 3D).

Second, increased breast density (particularly extremely dense breast tissue) is considered an independent risk factor for breast cancer. Although the degree of increased risk is highly debated, it is generally agreed that this risk is less than the major risk factors of age, family history, reproductive history, and genetic mutations.

What is the Arizona breast density law?

As of September 2018 legislation has been passed in 35 states requiring that women be informed of their dense breast tissue status as determined by the radiologist from a screening mammogram. Currently, laws vary from state to state concerning how the patient is notified, and what is included in the notification letter. As per the Arizona law the patient letter must include the following:

Your mammogram indicates that you have dense breast tissue. Dense breast tissue is common and is found in fifty percent of women. However, dense breast tissue can make it more difficult to detect cancers in the breast by mammography and may also be associated with an increased risk of breast cancer. This information is being provided to raise your awareness and to encourage you to discuss with your health care providers your dense breast tissue and other breast cancer risk factors. Together, you and your physician can decide if additional screening options are right for you.

A report of your results was sent to your physician.
This law has been in effect in Arizona since October 1st, 2014.

For more information regarding the etiology of this law please see the following link: “HAPPYGRAM”

Is screening digital mammography enough for women with dense breasts?

Conventional mammographic screening is the only early cancer detection strategy that has been shown in randomized trials to reduce the chance of death from breast cancer. Fourteen of the more recently published studies, between 2001 and 2010, have shown a 25-50% reduction in breast cancer-related mortality for women aged 40-74 years who had mammographic screening (Ref. 1). The American Cancer Society, the National Comprehensive Cancer Network, the American Congress of Obstetricians and Gynecologists, the American College of Radiology and other organizations recommend screening mammography annually for women older than 40 years. The Affordable Care Act, signed into law in 2010, mandated insurance coverage of annual mammograms for women commencing age 40.

Digital mammography is less effective at finding cancers in women with dense breasts as the superimposition of breast tissue can obscure cancers or make normal structures appear suspicious. This reduction in sensitivity and specificity for the detection of breast cancers is more pronounced as breast density increases (Illustration B). Breast density is assessed by your radiologist, at the time of your screening mammogram, using the breast image reporting and the data system (BIRADS), developed by the American College of Radiology. 50% of women have dense breasts. In these women, additional imaging might be considered to increase the likelihood of detecting early cancers. However additional imaging may result in additional costs, unnecessary anxiety, and biopsies with benign pathology results, which must be taken into consideration.

Breast Illustration

What adjunctive imaging options are available for women with dense breasts?

Bilateral Whole Breast Sonography:
Ultrasound (sonography) uses sound waves to image the breast. Ultrasound does not require compression of the breast, nor an intravenous injection of contrast. Bilateral whole breast sonography has been extensively evaluated as a potential screening test. In women with dense breasts, screening ultrasound detects additional cancers to those discovered with digital mammography. The number of new cancers found, is similar to that seen with 3D mammography. Unfortunately, employing ultrasound as a screening tool increases the number of unnecessary biopsies to an unacceptable level (Ref. 2). For this reason whole breast ultrasound is not offered at Radiology Ltd as a screening test.

3D Mammography:
3D Mammography takes multiple x-ray images of the compressed breast using different projections, and from this data reconstructs multiple thin images representing the breast volume. These images are then dynamically viewed by your radiologist, one after another, like a movie. Tomosynthesis helps to increase the conspicuity of cancers by removing the layers of overlapping breast tissue that occur with conventional digital mammography. It is most effective in breasts of mixed density as we see in women with heterogeneously dense breasts (Illustration D). Tomosynthesis detects on average an additional 1.9 cancers per 1000 screens when used in addition to digital mammography (Ref. 3-5). To put that into context, screening digital mammography alone, detected 5.2 cancers per 1000 screens in the same studies. The use of tomosynthesis in addition to screening digital mammography does increase the radiation dose to the breasts by a factor of 2. The total combined dose however, is still below the U.S.Food and Drug Administration (FDA) radiation dose limits allowed for mammograms and is similar to the dose patients received before the introduction of digital mammography. The radiation dose of a digital mammogram examination is however negligible, being equivalent to that received from normal background radiation over a period of seven weeks.

Bilateral Breast Magnetic Resonance Imaging:
Breast MRI is our most sensitive tool for the detection of breast cancer. Across 9 scientific studies MRI detected an additional 11 cancers per 1000 screens in high risk women (Ref. 6). Its performance is not affected by breast density nor the presence of breast implants. It is not associated with x-ray radiation, however, MRI does require an intravenous injection of contrast.

Why do women need to know lifetime breast cancer risk in addition to breast density status to determine which, if any additional screening options are appropriate?

Although adjunctive screening may be appropriate for all women with dense breast tissue, unfortunately insurance considerations will play a role in which options are pursued for most women. When insurance companies decide if additional screening examinations will be covered for women with dense breast tissue, they often take into account lifetime risk for developing breast cancer.

Breast cancer risk assessment identifies the small percentage of women who are at high risk for breast cancer and may not be aware of it. At Radiology Ltd. all patients referred for screening have their breast cancer risk estimated using the Tyrer-Cuzick statistical model as part of our Personalized Breast Screening Service. Personal and family history, as well as numerous additional risk factors, are incorporated into the Tyrer-Cuzick model. A woman with a greater than or equal to 20% lifetime risk of breast cancer, is considered at high risk. This information is included in every screening mammogram report.

Which adjunctive imaging option is best for me taking into account both breast density and breast cancer risk?

In March 2018 The American College of Radiology published the following article: “Cancer Screening in Women at Higher-Than-Average Risk: Recommendations from the ACR.” These recommendations should be discussed with your healthcare provider. Keep in mind that insurance coverage for breast cancer adjunctive screening is constantly evolving and this information should also factor into your discussion with your healthcare provider. Together you can decide which, if any, adjunctive imaging is right for you.

By age 30:

  • All women should be evaluated for breast cancer risk by their primary care provider.
  • Early breast cancer risk determination is particularly important for women of Ashkenazi Jewish descent and African American descent, as these women are at higher risk for genetic mutations which can lead to more aggressive young-onset breast cancers.

Average Risk Women (<10% lifetime risk of breast cancer):

  • Age 40: Begin annual screening mammography (either 2D or 2D + 3D)
    Women <50 years of age with dense breast tissue benefit the most from adding 3D mammography to the 2D mammogram.

High risk women AND their first degree relatives (e.g. mom, sister and daughter) due to:

  • specific genetic mutations determined through genetic testing
  • OR >20% lifetime risk:
    • Age 30: Begin annual screening mammography (either 2D or 2D + 3D)
    • Higher risk women who begin screening at an earlier age would be expected to benefit from 3D mammography given the known likelihood of having denser breast tissue.
    • Age 25-30: Breast MRI annually

Genetic counseling for hereditary breast and ovarian cancer syndrome (BRCA gene) has been recommended. What do I do next?

Genetic counseling for Hereditary Breast and Ovarian Cancer Syndrome is recommended in women who have an unusually strong personal and/or family history of breast and/or ovarian cancer as outlined by the USPSTF guidelines released in December 2013. Genetic counselors examine your family history in detail and help you decide if testing for the BRCA or other high risk genes is appropriate for you. A positive test for a high risk gene has important implications for you and your family. We advise you discuss our recommendation with your doctor to ensure this test is right for you.