Breastfeeding Reduces Breast Cancer Risk in Black Women

A large study bolsters the evidence that black women who breastfeed have a lower risk of being diagnosed with ER- and triple-negative breast cancer.

A large study bolsters the evidence that African American women who breastfeed have a lower risk of being diagnosed with estrogen receptor (ER)-negative and triple-negative breast cancer, which are difficult to treat. In general, studies have shown that African American women have a higher incidence of ER-negative and triple-negative breast cancer. The study, published in the Journal of the National Cancer Institute, was conducted by the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, a collaborative effort of four epidemiological studies.

Researchers analyzed questionnaire data from two case-controlled and two cohort studies of breast cancer among African American women, as well as more than 14,000 control patients. The results suggested that women who had given birth but did not breastfeed had an increased risk of ER-negative and triple-negative breast cancer.

The study found that African American women who had given birth had a 33% higher risk of ER-negative breast cancer and a 37% higher risk of triple-negative breast cancer compared with those women who had never given birth. However, the women who breastfed did reduce their risk of ER-negative breast cancer-though not ER-positive breast cancer (odds ratio of 0.81). The risk of ER-negative breast cancer increased with each subsequent birth among those women who did not breastfeed (odds ratio of 1.68 for four or more births compared with one birth for a woman who breastfed).

“Promotion of lactation may be an effective tool for reducing occurrence of the subtypes that contribute disproportionately to breast cancer mortality,” concluded the authors. The finding may explain why African American women, who typically have more children but have lower rates of breastfeeding compared with American white women, are disproportionately affected by ER-negative breast cancer, stated the authors.

Julie Palmer, ScD, of the Slone Epidemiology Center at Boston University, and colleagues analyzed 2,446 cases of ER-positive cancer, 1,252 cases of ER-negative cancer, and 567 cases of triple-negative cancer, pooling data from the Black Women’s Health Study, the Multiethnic Cohort Study, the Carolina Breast Cancer Study, and the Women’s Circle of Health Study.

“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 Christine B. Ambrosone, PhD, chair of the department of cancer prevention and control at Roswell 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, particularly for African American women.”

Still, future studies need to occur to understand how the length of breastfeeding affects the risk of these breast cancers.

“Beyond breastfeeding, there remains a need to identify the broader environmental, biological, and contextual factors that contribute to the incidence of and disparities in triple-negative breast cancer,” noted Amanda I. Phipps, PhD, and Christopher I. Li, MD, PhD, of the department of epidemiology at the University of Washington in Seattle, in an accompanying editorial. “Pooled studies, such as the AMBER Consortium, offer great potential for more detailed investigations into the epidemiology of this poor-prognosis disease subtype.”