Identifying Breast Cancer Risk Factors for Black Women.

Black women under the age of 45 are at increased risk for an aggressive form of breast cancer—estrogen receptor (ER) negative—if they experienced a high number of pregnancies, never breast fed, and/or had higher waist-to-hip ratio, according to a study co-authored by School of Public Health researchers.

The findings, published in Cancer Epidemiology, Biomarkers, & Prevention, are significant because they shed light on some “modifiable” risk factors, the researchers said.

Mortality from breast cancer is markedly higher in African American women as compared to white women in the US, in part because they are more likely to be diagnosed with ER-negative tumors, which are more aggressive and difficult to treat. African American women also are diagnosed with breast cancer at younger ages.

Researchers from BU’s Slone Epidemiology Center used 18 years of data from 57,708 African American women enrolled in the Black Women’s Health Study, a follow-up study of the health of African American women in progress since 1995. They evaluated the relation of reproductive factors, measures of body size, and other factors to the incidence of ER-negative and ER-positive breast cancer in both younger and older women.

“Very little is known about how young women can reduce their personal risk of ER-negative breast cancer,” said lead author Kimberly Bertrand, an epidemiologist at Slone and assistant professor of medicine at the School of Medicine. “Most exciting among our findings is that two of the factors we found to be important—breastfeeding and higher waist-to-hip ratio—are modifiable, which suggests opportunities for risk reduction or prevention.”

Co-authors on the study include Lynn Rosenberg and Julie Palmer, both professors of epidemiology affiliated with Slone. Traci Bethea, an epidemiologist at Slone and assistant professor of medicine at the School of Medicine, also contributed.

Funding for the study was provided by the National Cancer Institute.