Breast density, and how it affects the detection and treatment of breast cancer, is increasingly becoming a topic of discussion amongst patients, doctors and even politicians. Recent legislation passed in many states, including California, now require mammography centers to inform patients if they have dense breast tissue.

Dense breast tissue is made-up of more connective tissue than less dense, or fatty, breast tissue.  As a result, dense breast tissue appears more white on a mammogram, making it harder to identify some cancers. Equally important is the four-fold increased rate of breast cancer associated with increased breast density. That is to say that not only is it harder to detect breast cancer with a mammogram in patients with dense breasts, it is also more likely for patients with dense breasts to develop breast cancer.

Radiologists classify breast density into one of four types using the Breast Imaging-Reporting and Data System (BI-RADS) classification.

“Should Breast Density Influence Patient Selection for Breast-Conserving Surgery?”

During part of my training at Memorial Sloan Kettering Cancer Center in New York, I, along with several collaborators, decided to investigate breast density and it’s correlation with cancer development and treatment. In an earlier study, we found that patients with dense breasts were developing similar types of cancers as patients with fatty breasts, but they were more likely to undergo mastectomy. In my more recently published study, “Should Breast Density Influence Patient Selection for Breast-Conserving Surgery?”, we explored why this was happening.

We were interested in finding out why breast cancer patients with dense breasts were more likely to have mastectomies instead of breast-sparing surgery (lumpectomy) compared to cancer patients with less dense breasts. I was the first-author on this study involving 1,056 patients treated for breast cancer, and it was recently published in the February 2013 issue of the Annals of Surgical Oncology. I encourage you to view the full article.

One possible hypothesis was that patients with dense breasts were developing multiple areas of cancer in the breast (multifocal or multicentric breast cancer) that would prevent them from safely undergoing lumpectomy to remove all the cancer. Another possibility was that they were developing larger cancers or cancers with other characteristics such as extenstive intraductal component (EIC) that are known to lead to more margin positivity (cancer seen at the margin, or edge, of the lumpectomy) leading to further excisions and ultimately mastectomy in order to remove all the cancer in the breast.

We were surprised to find that none of these hypotheses were correct; instead, patients with dense breasts were frequently undergoing mastectomy without even attempting lumpectomy. They were not more likely to have cancer at the margins if they did have a lumpectomy compared to their less dense counterparts. Instead, more likely, these cancer patients with dense breasts were having mastectomies for other, more subjective reasons that could not be found in pathology reports or from their clinical histories.

Since we could not identify a clinical or pathologic factor associated with mastectomy selection in dense-breasted patients, I suspect there may have been a more hidden, emotional component involved in the decision for mastectomy. I wonder if many of these patients, and likely their treating physicians as well, may have chosen mastectomy instead of lumpectomy based on their breast density alone. Knowing the higher risk of cancer development in dense breasts and knowing the difficulty of detecting breast cancer in dense breasts, the fear of future breast cancers could have been enough to choose mastectomy over lumpectomy.

This study highlights the importance of not only knowing the biology of breast cancer and breast density, but the real, daily significance of understanding patient fear and their emotional vulnerability while making surgical treatment decisions. I do not believe that patients with dense breasts should all undergo mastectomy. I do believe, however, that educating patients about breast density is critical and that as clinicians we must help our patients make informed treatment decisions.