FRIDAY, Sept. 26, 2014 (HealthDay News) -- Black mothers who don't breast-feed may be at higher risk for an aggressive type of breast cancer, a new study suggests.
Researchers analyzed data from nearly 3,700 black breast cancer patients. About one-third of them had estrogen receptor-negative breast cancer -- a tumor subtype that is more common in black women and carries a higher risk of death.
Women with children were one-third more likely to develop these estrogen receptor-negative breast tumors compared to those who never had children, according to a team led by Julie Palmer, professor of epidemiology at Boston University's Slone Epidemiology Center.
However, whether or not a mother breast-fed her infants seemed to influence her risk for the tumor, the study found.
For example, the results indicated that women who had four or more children but had never breast-fed were 68 percent more likely to develop an estrogen receptor-negative breast cancer, compared to women who had only one child but did breast-feed.
Breast cancer cells are often influenced by the presence of estrogen if they have certain "receptors" on the surface of the cell. So, breast cancer subtypes include estrogen receptor-negative and estrogen receptor-positive tumors.
When it came to estrogen receptor-positive tumors, the study found that women who had four or more children had a slightly lower risk for these cancers, whether or not they had breast-fed their babies.
The findings were published this month in the Journal of the National Cancer Institute. The study was only designed to spot an association between a lack of breast-feeding and raised cancer risk, it could not prove cause and effect.
Prior research has found that the overall risk of breast cancer may be higher during the first five or 10 years after a woman gives birth, with a reduction in risk after that time. However, this study suggests that the risk for estrogen receptor-negative breast cancer, at least, may persist.
"Breast cancer mortality is disproportionately high in African American women of all ages, in part due to the higher incidence of estrogen receptor-negative breast cancer, with fewer targets for treatment," Palmer noted in a journal news release.
However, besides its well-known benefits for baby, breast-feeding may be a "factor that could prevent some cases of this breast cancer subtype and reduce the number of African American women dying from this disease," she added.
The American Cancer Society has more about breast cancer types.