Estrogen receptor(ER)-negative breast cancer is a tumor subtype that is more common in black women and carries a higher risk of death. A new, large study published in the Journal of the National Cancer Institute suggested that the reason why black women are at higher risk for this aggressive type of breast cancer may be because the breastfeeding rate among them is lower.
In other words, mothers who choose to not breastfeed may be at a higher risk of breast cancer than those who do.
The research effort is led by researchers at Roswell Park Cancer Institute, Boston University’s Slone Epidemiology Center and the University of North Carolina Linebarger Cancer Center.
The team looked at questionnaire data from several studies, including two cohort studies and two case-control studies of breast cancer in African-American women. They analyzed data from nearly 3,700 black breast cancer patients. About one-third of them had ER-negative breast cancer.
Researchers founded that women with children were one-third more likely to develop these type of breast tumors compared to those who never had children. However, whether or not a mother breastfed her infants seem to influence her risk for the tumor even more.
For example, the results indicated that women who had four or more children but had never breastfed were 68 percent more likely to develop an ER-negative breast cancer, compared to women who had only one child but did breastfeed.
“Promotion of lactation may be an effective tool for reducing occurrence of the subtypes that contribute disproportionately to breast cancer mortality,” Julie Palmer, a study co-leader and professor of epidemiology at Boston University’s Slone Epidemiology Center wrote.
The authors concluded that this study may explain, in part, why African-American women, who typically have more children but a lower prevalence of lactation than U.S. white women, are disproportionately affected by ER-breast cancer.
The study also found that black women who breastfeed have a lower risk of being diagnosed with triple-negative breast cancer, in which tumor cells test negative for three key hormone receptors thus is hard to treat. The authors suggest that triple-negative breast cancer in African-American women who have given birth could be lowered by almost two-thirds if they breastfed at a similar rate as non-Hispanic white women.
“These findings showing that breastfeeding can reduce the risk for African American women of getting aggressive breast cancers are exciting because this is something that can be acted upon, where we can actually prevent some cases of these often-deadly cancers,” said Dr. Christine B. Ambrosone, a study co-leader and chair of the department of cancer prevention and control at Rosewell Park Cancer Institute in Buffalo, New York, in a statement. “We already know that breastfeeding has so many benefits to babies and their mothers. This is one more reason to encourage and support breastfeeding.”
The new study provides the most conclusive evidence to date, but is not the first and/or only study that has shown a connection between the number of times a woman has given birth and increased risk of ER-negative tumors, and that breastfeeding reduced risk of these aggressive cancers.
Breastfeeding has long been recognized as one of the factors that reduce the risk of breast cancer. In her recent article published in Huffington Post, Dr. Marisa Weiss, the president and founder of breastcancer.org, wrote, “You can take steps to reduce your risk of the disease by maintaining a healthy weight…and breastfeeding your baby.”
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