The Density Debate
By Rebecca Montz, EdD, MBA, CNMT, PET, RT(N) (CT), NMTCB RS
Radiology Today      
Vol. 24 No. 4 P. 18

Empowering Women to Confront Dense Breast Tissue Concerns  

According to the CDC, about one in eight women will get breast cancer in their lifetime. Mammograms continue to be the gold standard in screening for early detection of breast cancer and determining whether a woman has dense breast tissue. The National Cancer Institute reports that nearly 50% of women 40 years old and older who have a mammogram are identified as having dense breasts, making it common among women. Having dense breast tissue is an independent risk factor for breast cancer and makes mammograms slightly less effective in early detection of breast cancer. However, most women are unaware of the fact that they have dense breast tissue or the possible impact it may have on their health. 

Breast tissue is composed of milk glands, milk ducts, supportive tissue (dense breast tissue), and fatty tissue (nondense breast tissue). Breast density is a measure of the amount of fibrous and glandular tissue, also known as fibro glandular tissue, in breasts as compared with fat tissue. If there is a large amount of fibrous and glandular tissue, it may be determined that the patient has dense breast tissue when seen on a mammogram. Concerns about dense breast tissue are that it makes breast cancer screenings more difficult to evaluate and also increases the risk of breast cancer.

Dense breast tissue appears white on mammograms. Various masses and cancers also appear white, making it more difficult for radiologists to differentiate fibrous and glandular breast tissue from abnormalities. In contrast, fatty tissue looks dark and transparent on mammograms; therefore, abnormalities are less likely to be obstructed. Although the challenges associated with dense breast tissue and mammograms are recognized, experts in the field do not agree on what other tests, if any, should be done in addition to mammograms for women with dense breasts.

Patient Advocacy
All women should be informed if they have dense breast tissue because breast density diminishes mammography’s ability to detect breast cancer, potentially resulting in a negative mammogram that may be a false reassurance, says Vivianne Freitas, MD, MSc, an assistant professor at the University of Toronto in Canada, and a staff radiologist at the Joint Department of Medical Imaging in Toronto. If a patient’s mammogram report states that they have dense breast tissue, it is vital they speak with their health care team to discuss the possibility of other health-related factors that may increase their risk for breast cancer. Promoting patient access to information in their mammography reports is an important part of a comprehensive breast health strategy.

In a significant effort to improve patient education and communication, the FDA on March 9, 2023, announced updates to the mammography regulations under the Mammography Quality Standards Act of 1992, a law passed to ensure quality mammography, and now requires all nationwide mammography facilities to notify patients about the density of their breasts. Previously, 38 states had this requirement, but facilities will now have 18 months to comply with the nationwide requirement. The amendments provide specific language explaining how breast density can influence the accuracy of mammography. The new rules mandate that providers include an assessment of patients’ breast density in mammogram reports to inform them about the potential limitations of their screenings and enable them to make informed decisions about further testing.

The new amendments will enhance the FDA’s ability to communicate directly with patients if facilities do not meet the quality standards. Patients receiving personalized information about their breasts will be more knowledgeable and aware of additional steps to take to ensure breast cancer does not go undetected. The FDA’s recent announcement will empower women to collaborate with their providers to make informed decisions about additional screening, if needed, and engage them in their health.

The current recommendation for breast cancer screening is mammography. The frequency and age of the screening are variable factors worldwide, depending on the screening program. However, most medical guidelines suggest women should start getting regular mammograms starting at age 50 or, depending on additional risk factors, earlier.

The American Cancer Society strongly recommends that women with an average risk of breast cancer undergo regular screening mammography starting at age 45. The United States Preventive Services Task Force (USPSTF) recommends women who are 50 to 74 years old and at average risk for breast cancer get a mammogram every two years. The USPSTF recommends that women weigh the benefits and risks of screening tests when deciding whether to begin getting mammograms before age 50. Brian Drohan, PhD, a scientist at Volpara Health, says the rising tide of interest in breast density and family history of cancer is helping drive changes in screening recommendations.

“As we work with breast centers around the world, we see many that are developing their own risk programs in lieu of clear guidelines, and they are finding more cancers earlier and reducing suffering for women and families,” he says.

Many Options
Several supplemental screening tests are available for women with dense breast tissue, but no established guidelines exist to direct health care providers in their recommendation of preferred supplemental screening tests. Drohan says that even though supplemental screening has been shown to find cancers earlier and find interval cancers, there is a lack of education and preparedness in the referring population that hinders patient education and access. He suggests that tailored screening, which takes into consideration a patient’s mammographic breast density and lifetime breast cancer risk, can help guide breast cancer screening strategies that are more comprehensive.

The four most common supplemental imaging tests are handheld breast ultrasound (HHUS), automated breast ultrasound (ABUS), digital breast tomosynthesis (DBT), and breast MRI. Studies have suggested that DBT, known as 3D mammography, may be particularly helpful for women with dense breasts. Additional studies have shown that HHUS, ABUS, and MRI may also be utilized to detect some breast cancers that could be missed on mammograms. Contrast enhanced mammography and molecular breast imaging are also emerging screening technologies being suggested for dense breasts.

The benefits of HHUS are that it is easily accessible, does not use ionizing radiation, is relatively inexpensive, and addresses patient comfort. The drawbacks are the potentially high number of call backs and false positive needle biopsies for incidental findings. The risks of call backs from additional testing may require the patient to endure additional mammograms, ultrasounds, or needle biopsies, which can lead to patient anxiety. However, women overall prefer to have been called back rather than have a missed cancer diagnosis, says Stamatia Destounis, MD, FACR, FSBI, FAIUM, the managing partner of Elizabeth Wende Breast Care in Rochester, New York; chair of the ACR Commission on Breast Imaging; and a member of Radiology Today’s editorial advisory board.

Like HHUS, ABUS can also increase cancer detection, but it has high recall and biopsy rates. Furthermore, ABUS guided biopsy has not been developed, so an additional HHUS is necessary for further evaluation and biopsy of findings recalled from ABUS, Freitas explains.

Is MRI Superior?
Recent studies have shown that breast MRI is highly effective as an additional method for breast cancer detection and works well in women with dense breast tissue. A recent study, “Supplemental Breast Cancer Screening in Women With Dense Breasts and Negative Mammography: A Systematic Review and Meta-Analysis,” published in Radiology, was conducted to measure which screening methods are the most beneficial to women with dense breasts. Researchers performed a meta-analysis on 22 studies that included 261,233 patients screened for breast cancer. Ten of the studies covered HHUS, four studies covered ABUS, three studies covered breast MRI, and eight studies reported on DBT. The meta-analysis revealed that, of 132,166 patients with dense breasts, a total of 541 breast cancers were initially missed on mammography but detected with supplemental screening methods. Breast MRI was the superior screening method and could detect even the smallest of cancers.

Excluding MRI, there was not a significant difference between the other supplemental screening methods. The study was the first of its kind to compare screening diagnostic performance of these modalities. Freitas, a coauthor of the study, says, “Our results about the role of MRI in supplementary screening will allow stakeholders to guide health care policies in this setting and direct further research.” She says that before advocacy can begin for wider application of breast MRI in women with dense breasts, further evaluation of the cost-effectiveness of breast MRI compared with other techniques, effect on mortality reduction, etc, will need to be studied.

Although breast MRI may be an effective screening test for women with dense breasts, it requires an injection of contrast media and uncomfortable positioning for some patients. Patients may be allergic to the contrast, be claustrophobic, or have metal from a prior biopsy/surgery in their body, ruling them out as candidates for MRI. Another drawback is the expense and potential lack of accessibility due to some radiology practices not having an MRI unit. As with HHUS and ABUS, MRI may potentially detect abnormalities other than cancer, which could lead to more tests and unnecessary biopsies.

Supplemental Screening
Overall, there are barriers to supplemental screening, such as the lack of precise guidelines and screening codes, unclear reimbursement policies, limited staff resources and equipment to provide the screening, and potential additional expense and stress for the patient. Freitas says, “At the current time, availability and cost of the breast MRI remain the biggest barrier for widespread implementation.” She notes that abbreviated MRI demonstrated a similar sensitivity and specificity compared with a full breast MRI protocol and is being investigated to provide a more cost-effective modality.

Supplemental screening will increase the cancer detection rate and likely find interval cancers when they are smaller and more treatable, but it may lead to overdiagnosis due to false positives. However, Drohan says, “If we are going to inform women their mammogram is less effective because they have dense breasts, we need to inform them of the pros and cons of supplemental screening, which may include overdiagnosis.”

Drohan believes the ideal scenario would include adjunct screening as part of a risk assessment program that brings together a multidisciplinary care team within an institution to personalize breast care. He says care teams can provide a collaboration point for radiologists, oncologists, nurse navigators, genetic counselors, and medical geneticists to provide a more complete standard of care for patients.

The debate about which women should receive supplemental screening and which modalities should be applied based on the level of their dense tissue and other risk factors is ongoing. But experts agree that women with dense breast tissue should have the opportunity to discuss their options with their health care providers. “A shared decision-making model is necessary, where the health care provider and a patient work together to make the best decision for supplementary screening, taking into consideration the provider’s knowledge and experience, evidence based information about different options, and the patient’s values and preferences,” Freitas says. The goal is to find every breast cancer as soon as possible to increase long-term survival and improve each patient’s overall prognosis.

— Rebecca Montz, EdD, MBA, CNMT, PET, RT(N) (CT), NMTCB RS, has worked at the Mayo Clinic Jacksonville and University of Texas MD Anderson Cancer Center in Houston as a nuclear medicine and PET technologist.