Breast Density Not Linked to ER-PR- Breast Cancer Risk
Posted Jan 19 2011 10:37am
Breast density as measured by mammograms (mammographic breast density) is a well know risk factor for breast cancer. Women who have a high percent of dense breast tissue have an increased risk for developing breast cancer. However, it is unclear whether mammographic breast density affects the risk of specific subtypes of breast cancer as defined by estrogen receptor (ER) and progesterone receptor (PR) status.
Women who participated in the Hawaii section of the Multiethnic Cohort Study were asked to participate in a new breast cancer research study where the investigators used mammograms to assess breast density in 667 healthy control women and 607 breast cancer patients. Breast cancer tumors were defined by hormone receptor status as ER+PR+, ER-PR-, ER+PR-/ER-PR+, or unknown. The study investigators then analyzed the link between breast density as measured with mammograms and the chances of developing breast cancer. The researchers reported
Average percent breast density was greater for ER+PR+ tumors (37% dense) compared to controls (29%) and ER-PR- tumors (29%).
A 10% increase in mammographic breast density was linked to a 26% increased risk for ER+PR+ breast cancer and a 23% increased risk for ER+PR-/ER-PR+ breast cancers.
Mammographic breast density did not affect ones risk for ER-PR- breast cancer.
This is a very interesting study that starts to more clearly define the breast cancer risk associated with increased breast density. This study suggests that breast density, while clearly a risk factor for hormone receptor positive breast cancers, does not increase the risk of ER-PR- breast cancers. Hormone receptor negative breast cancers are typically more aggressive and associated with worse outcomes. Additionally, the chances of developing ER-PR- breast cancer has been reported to be higher in African-American women and in women who have used oral contraceptives for longer than 10 years. It is clear that different breast cancer subtypes have different risk factors and determining which risk factors are linked to which types of breast cancer is an important part of our fight against breast cancer.