Abstract LB-13: Early life exposures and breast cancer (BC) risk among African American (AA) and European American (EA) women.
Authors: Glasgow Mark L. , Freudenheim Jo , Zirpoli Gary , Bandera Elisa , Ambrosone Christine 
Published: August 2014

Background. There is evidence to suggest that early life exposures including birthweight, history of having been breastfed during infancy, in utero exposure to maternal smoking, and parental education are associated with BC risk. Potential underlying mechanisms include variability in exposure to maternal endogenous sex and growth hormones. Also, parental socioeconomic status may be a proxy for environmental characteristics that impact biological processes in early life, and ultimately influence BC risk. Research has focused on EA women; relatively little is known about associations between early life exposures and BC risk for AA women.

Methods. We conducted a case-control study in AA and EA women aged 22-75 years living in metropolitan New York City and eastern New Jersey (Women's Circle of Health Study). Breast cancer cases (AA n=827; EA n=772) were diagnosed with primary, incident, histologically confirmed invasive BC or ductal carcinoma in situ. Controls (AA n=905; EA n=715) were frequency matched to cases on age and race. Birthweight, history of having been breastfed during infancy, history of in utero exposure to maternal smoking, and parental education were by self-report using an interviewer-administered questionnaire.

Results. Birthweight was not significantly associated with BC risk in this study for AA or EA women. Having been breastfed during infancy was associated with significantly increased BC risk for both groups (ORAA=1.60, 95% Cl: 1.27-2.02; OREA=1.45, 95% Cl: 1.14-1.85). For EA women, but not AA women, reporting in utero exposure to maternal smoking was associated with significantly decreased BC risk (OR=0.61, 95% Cl: 0.45-0.82). Among AA women, those born to mothers with at least a college degree had a significantly lower BC risk compared to AA women born to mothers with a high school or less education (OR=0.67, 95% Cl: 0.49-0.93). Among EA women, we found no association with maternal education. However, EA women born to fathers with at least a college degree had a significantly lower BC risk compared to EA women born to fathers with a high school or less education (OR=0.65, 95% Cl: 0.51-0.84).

Conclusions. Our findings support the hypothesis that early life exposures impact adult BC risk. History of having been breastfed during infancy, in utero exposure to maternal smoking, and parental education were all associated with BC risk. While minor differences in risk estimates were found between EA and AA women, associations were similar.

Citation Format: Mark L. Glasgow, Jo Freudenheim, Gary Zirpoli, Elisa Bandera, Christine Ambrosone. Early life exposures and breast cancer (BC) risk among African American (AA) and European American (EA) women. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-13. doi:10.1158/1538-7445.AM2013-LB-13