| Births, breastfeeding rates may explain breast cancer disparities

A new study may better explain why African American women have greater risk for developing more aggressive and difficult-to-treat forms of breast cancer, called estrogen and progesterone receptor negative cancers (ER-/PR-). The findings appear in the journal Cancer Epidemiology, Biomarkers and Prevention.

Breast cancer is the second-most common type of cancer among women, after skin cancer. While white women are slightly more likely to get breast cancer than African American women, African American women are more likely to die from breast cancer, according to?the American Cancer Society, because they are more likely to develop more aggressive breast cancers. But why this happens has been less clear.

Researchers at Boston University?s Slone Epidemiology Center analyzed data from the Black Women?s Health Study, which began in 1995 and? follows 59,000 African American women who complete health questionnaires every two years.

From 1995 to 2009, 457 women developed?estrogen and progesterone receptor positive cancers, ER+/PR+.

When a woman?s breast cancer cells are classified as hormone receptor positive it means they are more likely to respond to therapies that block the hormones from binding to receptors on cells. This is a less aggressive and more easily treated type of breast cancer.

During the same period, 318 cases of ER-/PR- cancers, the more aggressive and difficult-to-treat form of breast cancer, developed among the 59,000 women.

Women who gave birth to two or more children had a 50% associated increase in aggressive ER-/PR- cancer, but the association was not found when the women had breastfed. Other studies have also found an association between breastfeeding and decreased cancer risk.

The results were ?strikingly different? when researchers compared the number of births and breastfeeding among women with hormone receptor positive cancers. Women who had two or more children had lower associations of ER+/PR+ cancers, and breastfeeding didn?t change that association.

The authors conclude that their findings suggest that more births among African American women are associated with greater risk for more aggressive ER-/PR- breast cancer, and ?because African American women have had more births on average than U.S. white women, this association may? at least partially, explain the higher rates of those cancers among African American women. The authors suggest that efforts to encourage breastfeeding among African American women may help to reduce the number of these deadly types of cancers that disproportionately affect African American women.

Source: http://thechart.blogs.cnn.com/2011/08/16/births-breastfeeding-rates-may-explain-breast-cancer-disparities/

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