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AMBER Study Finds Evidence that Breastfeeding Can Help Prevent Aggressive Breast Cancer in African Americans

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Consortium study finds significant reduction in risk of ER-negative cancers in women who have breastfed.

Wed, May 13th 2015 03:30 pm

As part of the collaborative AMBER consortium, researchers from Boston University's Slone Epidemiology Center, Roswell Park Cancer Institute and the University of North Carolina Lineberger Cancer Center published findings indicating that African American women may be able to significantly reduce their risk of developing an aggressive form of breast cancer by breastfeeding.  The study was published in the September 15, 2014 issue of the Journal of the National Cancer Institute.

African-American women have a disproportionately high incidence of two aggressive forms of breast cancer: estrogen-receptor-negative (ERnegative) and triple-negative breast cancer, in which tumor cells test negative for three key hormone receptors used to determine treatment regimens. Earlier studies have shown a connection between the numbers of times a woman has given birth, and increased risk of ER-negative tumors, and that breastfeeding reduced the risk of these aggressive breast cancers.  Researchers from the three institutions combined data from four epidemiologic studies with large numbers of African-American participants: the Black Women's Health Study (BWHS), Multiethnic Cohort Study (MEC), Carolina Breast Cancer Study (CBCS) and Women's Circle of Health Study (WCHS). This new study combining breast cancer data provides the most conclusive evidence to date of these connections.   AMBER researchers looking at questionnaire data from these studies found that 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 than those who had never given birth. Breastfeeding modified the association, however; women who had breastfed had a lower risk of ER negative and triple negative breast cancer than women who had never breastfed.

"Our findings suggest that parous women are at increased risk of ER-negative and triple-negative breast cancer, and that lactation may ameliorate the effects of pregnancy and childbirth," the authors note. "These findings showing that breastfeeding can reduce the risk for African-American women on getting aggressive breast cancers are exciting because this is something that can be acted upon". The authors note that information on length of lactation, exclusivity of breastfeeding, or characterization of weaning was not available for all women in the study, and that they were therefore not able to estimate the minimum duration required for a reduction in risk of ER-negative cancer.

Complete details on this study can be found in the article published in the Journal of the National Cancer Institute:

Parity, lactation, and breast cancer subtypes in African American women: results from the AMBER Consortium.Palmer JR, Viscidi E, Troester MA, Hong CC, Schedin P, Bethea TN, Bandera EV, Borges V, McKinnon C, Haiman CA, Lunetta K, Kolonel LN, Rosenberg L, Olshan AF, Ambrosone CB. J Natl Cancer Inst. 2014 Sep 15;106(10). PMID: 25224496