I feel dense for not knowing this important public health fact: women with extremely dense breast tissue are at least four times more likely to develop breast cancer.
Over the years, I’ve had my routine screening mammograms with stellar results. No evidence of cancer in my two mammary glands. I’ve heard radiology technicians comment about my dense breasts, but I thought it was an interesting attribute like droopy breast, or perky breasts or double D breasts.
In December 2011, just before my 50th birthday, I was overdue for my routine screening mammogram. I felt a little guilty for putting it off, but the results were the same as always:
“Bilateral mammography shows extremely dense breasts throughout which are scattered with occasional benign microcalcifications bilaterally. Breast pathology is not suggested. Recommendation: Annual screening mammography.”
Just like always, my mammogram results showed nothing to worry about. Pencil on the calendar my next mammogram in 12 months.
Fast forward five months. My left nipple starts looking sorta like this and I made an appointment with my local nurse practitioner. A few diagnostic tests later and here’s the diagnosis: Stage IIIB invasive ductal carcinoma. In plain English, I have a 7 cm tumor in my breast that’s already spread to my lymph nodes.
“Seriously? 7 cm? What about that mammogram I had just a few months ago?” I ask myself and the physicians. “Mammograms are like reading the clouds,” one radiologist responded. “And you have really dense breast tissue,” he added.
Breast tissue density is a mammographic indicator of the amount of glandular tissue in the breast relative to fatty tissue. There are two qualitative classification systems to characterize it, the Wolfe grade and the American College of Radiology’s BI-RADS. What I didn’t know—-and feel ignorant for not knowing—-is high breast tissue density is a strong independent risk factor for developing breast cancer. Epidemiological studies consistently find a 4- to 6-fold increased risk of breast cancer for women with high breast density compared to those with less dense breasts (e.g., here, here, here.) Epidemiologists Valerie McCormack, PhD, MSc and Isabel dos Santos Silva, MD MSc PhD of the London School of Hygiene & Tropical Medicine conducted a systematic review and meta-analysis of 15 studies that used quantitative methods to assess mammographic density and breast cancer risk. In their 2006 paper published in Cancer Epidemiology, Biomarkers and Prevention they reported:
“The combined data presented here confirm that breast density, measured using either Wolfe grade or percentage density, is strongly associated with breast cancer risk, as determined by general population studies of either incident or prevalent cancer risk.”
I created the following table using McCormack and dos Santos Silva’s calculations of combined pooled relative risks (RRs) for breast tissue density categories.
My December 2011 written mammogram result merely said “extremely dense breasts.” I know now that meant my breasts reside in the >74% category. Based on McCormack and dos Santos Silva’s analysis, on the breast-density factor alone, women like me have an increased risk of breast cancer that is 3.64 to 5.91 times higher than women in the <5% breast density category.
The authors also qualify their statement with the following:
“the true association may be even stronger, as non-differential measurement error of breast density would lead to underestimation of associations. Assuming moderate error (intraclass correlation of 0.90), RR estimates for categories 50% to 74% and ≥75%, when corrected, would increase to 3.29 and 5.50, respectively.”
The more I started looking at the scientific literature, the more I found, and the more dense I felt. Writing in 2008 in the British Journal of Cancer, researchers with the Ontario Cancer Institute in Toronto wrote:
“…Extensive breast density is therefore one of the strongest known risk factors for developing breast cancer, second only to age and carrying a BRCA1 or BRCA2 mutation. Although less than 5% of unselected breast cancer patients have a BRCA1 or BRCA2 mutation, extensive mammographic density is common among women with breast cancer, and estimates of attributable risk show that densities in more than 50% of the breast may account for about a third of all breast cancers.”
On a mammogram, fatty breast tissue is radiolucent and appears black, while connective tissue absorbs x-rays and appears white. It is this denser tissue comprised of collagen, stromal tissue and epithelium cells that are correlated with breast density and make abnormalities more difficult to distinguish on mammograms. But the increased risk is not simply a failure of the human eye reading mammograms. Researchers have several hypotheses on potential biological mechanisms to link mammographic density and breast cancer risk.
For all these years, I’ve known some of the highest risk factors for the disease, such as being over age 65 years, inheriting the BRCA1 and/or BRCA2 genetic mutation, receiving high-dose radiation to the chest, and having two first-degree relatives (i.e., mother, sisters) with breast cancer (see page 12, Figure 4 in ACS Breast Cancer Facts & Figures, 2011.) But breast density, how’d I miss that one?
Now I’ve learned I’m not the only one. The Density Education National Survivors’ Effort (D.E.N.S.E.) are other women like me who:
“…received–year after year—the one sentence lay report either stating ‘No evidence of cancer’ or ‘Results of your recent mammography examination are normal/benign (not cancer.)’” The group says: “… A letter indicating ‘no cancer’ is clearly an inaccurate representation of reality if a radiologist knows that, due to density, there is a significant chance a tumor could be missed. If a ‘summary’ of a mammography report doesn’t include any mention of breast density, its inherent risk, and the possible limitations of a mammogram in finding a tumor because of density, then one has to wonder what its purpose is at all. …When women aren’t told about their own breast density and its inherent risk, they are denied the opportunity to protect and advocate for themselves.”
D.E.N.S.E. and other health-promotion groups worked with lawmakers in the Connecticut to pass a law in 2009 requiring radiologists to inform woman receiving mammograms about their breast density. The law includes the following provision:
“… each mammography report provided to a patient shall include information about breast density, based on the BI-RADS by the American College of Radiology. Where applicable, such report shall include the following notice: ‘If your mammogram demonstrates that you have dense breast tissue, which could hide small abnormalities, you might benefit from supplementary screening tests, which can include a breast ultrasound screening or a breast MRI examination, or both, depending on your individual risk factors. A report of your mammography results, which contains information about your breast density, has been sent to your physician’s office and you should contact your physician if you have any questions or concerns about this report.’”
Similar laws have been passed in Texas (effective date May 1, 2012), Virginia (effective date July 1, 2012), and New York (effective date January 2013), with varying degrees of specificity in the text of the required notice. Some organizations representing radiologists have argued that women would be alarmed unnecessarily by the notice. In some cases, they’ve succeeded in getting it toned down. At the federal level, Rosa deLauro (D-CT) and Steve Israel (D-NY) introduced the Breast Density and Mammography Reporting Act of 2011 (H.R. 3102) which would require radiologists performing mammogram to report breast density findings to physicians and patients.
I’ve been keeping friends and colleague apprised via CaringBridge on the initial phases of my treatment. I’ve happily heard from a few who’ve said “I’m one of those dense-breasted woman, too.” I responded to a few with this about my December 2011 mammogram:
“Hello! why don’t they put at least an asterisk after ‘extremely dense breast tissue’ that says ‘you are at higher risk of breast cancer’? Better yet, why aren’t ultrasounds part of the standard screening protocol for women with dense breasts? The mammogram that couldn’t distinguish my 7 cm tumor or the smaller tumors around it, gave me a ridiculous false sense of health.”
Now I know there are individuals across the country trying to get laws passed to do exactly that. How could I be so dense?