Breast Density and Breast Cancer Risk

3 December 2015

Dense breast tissue has been linked to an increased risk of developing breast cancer, although studies report a variable influence of breast density compared to other known risk factors.  A new study published in the journal European Radiology calls into question the association of breast density and breast cancer.

Researchers evaluated MRI scans to determine breast density as well as the degree of fatty tissue in women with and without breast cancer. They found a strong correlation between increasing age and amount of fatty tissue with breast cancer, but did not note an association between breast density and breast cancer. They noted that younger women tend to have dense breast tissue, but also tend to be leaner; increasing age and increased body fat are known to be associated with an increased risk of developing breast cancer.

Another study, presented at the Radiological Society of North America 2015 Meeting also evaluated the link between breast density and breast cancer. This study, performed by researchers in Croatia, evaluated almost 53,000 mammography examinations performed over a 5 year period. 230 women were diagnosed with breast cancer during the study period. The researchers expected to see more breast cancers in the group with dense breasts, but they found similar rates of cancer in those with dense versus fatty breast tissue. Approximately 17% of patients were determined to have dense breast tissue, so it is unclear if the results of this population can be applied to the United States population, where approximately 50% of women are estimated to have dense breast tissue. There was also relatively short follow up. In addition, this was an abstract presentation at a meeting – a peer-reviewed manuscript has not yet been published.

Neither of these studies answer the question regarding the link between breast density and breast cancer, but both suggest that breast density may simply be one piece of the puzzle. It is important to keep focus on the modifiable factors that contribute to an increased risk of developing breast cancer, such as obesity, inactivity, and alcohol intake.

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