Breast Density in the News 2019

Thirty-eight states have passed legislation mandating that a woman’s mammogram report include information about her breast density.  The Food and Drug Administration has been mandated to make sure all mammography reports include this information.  However, why this focus on breast density?  The National Breast Cancer Coalition published the following informative response in its recent “Call To Action” newsletter:

 

The National Breast Cancer Coalition (NBCC) is an evidence-based organization. What does that mean? We do NOT want women and men to get advice and information that is based on hope or assumptions. They deserve recommendations that are based on scientific evidence when it exists and to be told when it does not.  To do otherwise risks creating unnecessary harm. This is an important concept not just for the public, but for Congress as well. Legislators must stop enacting laws that fly in the face of scientific evidence.

On February 15, 2019, Congress passed a funding bill[1] that ended the longest ever Federal government shutdown. Unfortunately, this bill did many other things, including issuing a mandate to the U.S. Food and Drug Administration (FDA) about mammography screening and breast density reporting. Specifically….

The Committee recognizes the importance of patients receiving their own personal medical information and directs the Food and Drug Administration to ensure that mammography reports and summaries received by patients and their providers include appropriate information about breast density specified by the Secretary, including, at a minimum, the effect of breast density in masking the presence of breast cancer on a mammogram, the qualitative assessment of the provider who interpreted the mammogram, and a reminder to patients that individuals with dense breast tissue should talk with their providers if they have any questions or concerns about their summary“ (emphasis applied).

Why does Congress want you to know if you have dense breasts?  There really is no good reason. Unfortunately, as of May 2019, a total of 38 states and the District of Columbia have passed varying legislation requiring that women with dense breasts be notified about their breast density. Now the United States Congress wants to make the same mistake and raise it to the national level.

So, what is appropriate information in this instance?

What is Breast Density

Dense breasts are defined by how they appear on a mammogram using the American College of Radiology’s (ACR’s) Breast Imaging Reporting and Data System (BIRADS). This system classifies breasts as “almost entirely fatty,” “scattered fibroglandular densities,” “heterogeneously dense,” or “extremely dense.” With those classifications, approximately 43 percent of all women between the ages of 40 and 74 years have dense breasts (either “heterogeneously dense” or “extremely dense). The problem with this system is that there is considerable variability and subjectivity among radiologists in classifying breast density for patients. Studies have shown that density status is reclassified on subsequent examination for 1 in 5 women (23%) by the same radiologist, and for 1 in 3 women (33%) by a different radiologist.[2] Why should we care?

Breast Density and Mammography

Much of the push for notification is based on the assumption that if you have dense breasts, a mammogram is less likely to “find” a lump.  The thought is, if you have dense breasts and a normal mammogram, you should have additional screening. Of course, that will result in harm to women and significant unnecessary cost to the system, but what benefit would it have? One recent analysis[3] looked at the impact in New Jersey of density reporting requirements on the use of additional screening following normal mammograms in women with high density breasts. It demonstrated a 651 percent increase in the use of ultrasounds for supplemental screening, and a 59 percent increase in the use of breast MRIs. This has huge cost implications for the U.S. health care system when one considers how common dense breast are (43% of all women).[4]

While these additional imaging procedures can detect a small number of cancers missed by mammography, they will also dramatically increase the number of false-positive results which lead to additional procedures, including unnecessary biopsies and their associated risk. And we can’t ignore the potential risks that supplemental screening modalities themselves pose to patients, such as the use of gadolinium contrast required for breast MRI which has been associated with nephrogenic systemic fibrosis in patients with acute kidney injury or chronic kidney disease,[5] and more recent research has shown that IV gadolinium exposure may be associated with neuronal tissue deposition, even with normal renal function.[6] Likewise, harms from digital breast tomosynthesis could come from additional breast radiation exposure.[7]

This proposed national rule change will almost certainly expand the already too high rate of breast cancer testing and overdiagnosis[8] (~20%)—the identification of slow-growing, harmless cancers that won’t kill a person and don’t need to be found and treated in the first place, with resulting over treatment. This is simply not acceptable without solid evidence of benefit in patient-relevant survival outcomes. It may benefit the medical imaging community and oncologists, but not women.

Breast Density and Risk of Dying of Breast Cancer

If a woman has dense breasts is she more likely to die of breast cancer? No. Scientific studies have shown that among women ultimately diagnosed with breast cancer, increased breast density is not related to breast cancer death.[9] [10] [11] [12] [13]

In 2012, investigators10 actually studying this question using data from the Breast Cancer Surveillance Consortium (BCSC) concluded that high mammographic breast density is notassociated with increased risk of death from breast cancer or death from any cause after accounting for other patient and tumor characteristics. Likewise, in 2018 another group of researchers using data from the Population-Based Research Optimizing Screening Through Personalized Regimens (PROSPR) consortium similarly demonstrated that breast density is not associated with breast cancer that has a poorer prognosis.[14] Both of these studies are consistent with the U.S. Preventive Services Task Force (USPSTF) conclusions in the comprehensive synthesis it prepared on this topic in 2016.8 Thus, the requirement to provide notification about the status of breast density lacks any supporting evidence to do so, and in such a limited context is likely to be confusing, anxiety-provoking, and not at all informative for patients.

Breast Density and Risk of Getting Breast Cancer

Does having dense breasts raise your risk of getting breast cancer? Some evidence suggests that it may pose a small risk, but there are many known risk factors, most of which, including density, cannot be changed. Moreover, breast density ranks much lower in terms of absolute risk compared to other risk factors: age, family history, obesity, genetics; notifying patients about their breast density elevates this one risk factor out of context. Moreover, women receiving normal or low breast density assessments may erroneously be given a false sense of security and not consider their other more important individual risks… assuming of course they can do something about them, other than worry.

FDA must involve educated advocates in determining how to respond to this Congressional mandate, including the drafting of ANY information that will be provided to patients. Moreover, information to be included in the lay summary that is ultimately given to patients must explain the limitations of mammography and other screening modalities, the potential for overdiagnosis and overtreatment and the fact that there is no evidence that information about breast density would lower risk of getting or dying of breast cancer. Or have any benefit at all.


[1] Hoeven  J. Agriculture, Rural Development, Food and Drug Administration and Related Agencies Appropriations Bill of 2019, S 115-259, 115th Cong, 2nd Sess (2018).https://www.congress.gov/congressional-report/115th-congress/senate-report/259/1?q=%7B%22search%22%3A%5B%22farm%22%5D%7D. Accessed May 23, 2019.

[2] Sprague BL, Gangnon RE, Burt V, Trentham-Dietz A, Hampton JM, Wellman RD, et al. Prevalence of mammographically dense breasts in the United States. J Natl Cancer Inst. 2014;106.

[3] Sanders LM, King AB, Goodman KS. Impact of the New Jersey Breast Density Law on Imaging and Intervention Volumes and Breast Cancer Diagnosis. J Am Coll Radiol. 2016 Oct;13(10):1189-1194.

[4] Sprague BL, Gangnon RE, Burt V, Trentham-Dietz A, Hampton JM, Wellman RD, et al. Prevalence of mammographically dense breasts in the United States. J Natl Cancer Inst. 2014;106.

[5] Fraum TJ, Ludwig DR, Bashir MR, Fowler KJ. Gadolinium-based contrast agents: A comprehensive risk assessment. J Magn Reson Imaging. 2017 Aug;46(2):338-353.

[6] McDonald RJ, McDonald JS, Kallmes DF, et al. Intracranial Gadolinium Deposition after Contrast-enhanced MR Imaging. Radiology. 2015 Jun;275(3):772-82.

[7] Miglioretti DL, Lange J, van Ravesteyn N, et al. Radiation-induced breast cancer and breast cancer death from mammography screening. AHRQ Publication no. 14-05201-EF-5. Rockville, MD: Agency for Healthcare Research and Quality; 2015.

[8] Welch HG, Prorok PC, O’Malley AJ, Kramer BS. Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness. N Engl J Med. 2016 Oct 13;375(15):1438-1447.

[9] Siu AL. Screening for breast cancer: US Preventive Services Task Force recommendation statement. Ann

Intern Med. 2016;164(4):279–296.

[10] Weinstein SP, Localio AR, Conant EF, Rosen M, Thomas KM, Schnall MD. Multimodality screening of

high-risk women: a prospective cohort study. JClin Oncol. 2009;27(36):6124–6128.

[11] Kuhl CK, Strobel K, Bieling H, Leutner C, Schild HH, Schrading S. Supplemental breast MR imaging screening

of women with average risk of breast cancer. Radiology. 2017;283(2):361–370.

[12] Berg WA, Zhang Z, Lehrer D, et al. Detection of breast cancer with addition of annual screening ultrasound or

a single screening MRI to mammography in women with elevated breast cancer risk. JAMA. 2012;307(13):1394–1404.

[13] Gierach  GL, Ichikawa  L, Kerlikowske  K,  et al.  Relationship between mammographic density and breast cancer death in the Breast Cancer Surveillance Consortium.  J Natl Cancer Inst. 2012;104(16):1218-1227.

[14] McCarthy  AM, Barlow  WE, Conant  EF,  et al; PROSPR Consortium.  Breast cancer with a poor prognosis diagnosed after screening mammography with negative results.  JAMA Oncol. 2018;4(7):998-1001.