Abstract
Background: Body size is a modifiable risk factor associated with postmenopausal breast cancer in US White women. However, in African-Americans, there have been fewer studies and relationships are not well established.
Aims and Methods: We investigated the association between breast cancer risk and body size in childhood, young adulthood, and near the time of breast cancer diagnosis using data from the Carolina Breast Cancer Study, a 1993-2001 population-based case-control study of African-American (AA) cases (343 premenopausal, 445 postmenopausal) and controls frequency-matched by age and race. We investigated whether a) self-reported body size at age 10, age 18, age 35, and a year before interview and b) nurse-measured BMI, waist circumference, and waist-to-hip ratio (WHR) at interview were associated with cancer risk. Logistic regression models were adjusted for age, family history of breast cancer, education level, alcohol use, age at menarche, parity, age at first birth, and lactation.
Results: For premenopausal AA women, larger body size tended to be positively associated with cancer risk. The strongest results were for WHR (0.84+ vs <0.77): OR=2.00 [1.28, 3.13]). For postmenopausal women, body size was not significantly associated with risk, but weak inverse associations with higher adiposity were observed for nurse-measured BMI, weight at age 10, and possibly WHR (0.84+ vs <0.77) (OR=1.20 [0.76, 1.89]).
Conclusions: Associations between body size and breast cancer risk varied by menopausal status, measure of adiposity, and timing in the lifecourse. Strikingly, associations were not in the direction expected from the previous literature, which is based predominantly on Caucasian women. In fact, body size associations for premenopausal AA women may be inverse of that observed in Whites.
Impact: African-American women have higher risk of breast cancer at young ages (<40 years), but the causes of this disparity are not well understood. Given that the prevalence of obesity is high among African American women, understanding how body size relates to their risk of premenopausal breast cancer may offer insights for prevention.
Citation Format: Whitney Robinson, Chiu Kit Tse, Andrew F. Olshan, Melissa Troester. Body size across the lifecourse and risk of breast cancer in African American women, the Carolina Breast Cancer Study. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C84. doi:10.1158/1538-7755.DISP13-C84
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