AACR 2015
Black women found to have denser breast tissue than white women
Dr Anne Marie McCarthy - Massachusetts General Hospital, Boston, USA
Breast density is a strong risk factor for breast cancer. Women who have dense breasts have a 4-6 times greater risk of breast cancer than women with less dense breasts. We know that black women in particular have a high breast cancer mortality, higher than white women in the US. Black women also tend to be diagnosed at younger ages and with higher stage cancer than white women.
We were interested in whether breast density may differ between black and white women. The literature is mixed as to whether there are racial differences in breast density because many factors that affect breast density also differ by race ethnicity. So we compared breast density using quantitative measures that were derived from a computer algorithm to compare breast density levels for black and white women who underwent mammography screening. We had mammography images and then we had information on women’s body mass index as well as hormone use and reproductive factors so we were able to account for these factors when we compared breast density levels.
How many women did you look at and what did you find?
We had a little over 2,500 women in our study, about 1,500 black women. We found that even after we accounted for factors like age and BMI and hormone use, black women had higher breast density levels than white women using our quantitative measures.
What are the practical implications of that finding?
It’s important to understand risk factors for breast cancer and we need to be able to identify women who are at highest risk of breast cancer to be able to target appropriate prevention strategies for them. So it’s important to understand racial differences in breast density to be able to target women with highest risk of breast cancer with appropriate screening strategies. It’s important to understand who is at highest risk to be able to think about how often women should be screened and at what age and also with what modality. We know that breast density can make mammography less sensitive because it can be difficult to detect a cancer in women with dense breasts so perhaps in some women with very dense breasts they may elect to be screened with more sensitive technology such as MRI or breast ultrasounds.
How do you think this is going to, or should, impact the screening programme nationally?
I think we need to do some additional work to see if our findings that black women at higher breast density are replicated. We’re planning that study now, we have a larger population that we’re going to look at. But this is one of the first studies that has used quantitative measures of breast density specifically in a large population of black women.
It’s important that cancer doctors understand the importance of breast density as a risk factor for breast cancer, particularly because in the US several states have passed legislation that mandate notification of women if they have dense breasts. So there’s going to be conversations between women and their physicians about what this means and what the implications are, both for their cancer risk and for their cancer screening behaviours.
