There is convincing evidence that obesity is inversely associated with breast cancer risk in premenopausal women, while increasing risk in postmenopausal women. However, this is based on studies largely conducted in Caucasian populations. Associations in African American women, who have a higher prevalence of obesity, have been evaluated in few studies and results are inconclusive. We evaluated the impact of body size, body fat distribution, and body composition on breast cancer risk among African American (AA) women (810 cases and 1022 controls) participating in the Women's Circle of Health Study (WCHS). WCHS is an on-going multi-site case-control study in New York City (NYC) and New Jersey (NJ), which includes African American and Caucasian women. Cases were newly diagnosed, histologically confirmed ductal carcinoma in situ or invasive breast cancer, age 20-75 yrs. Controls were frequency matched on age to the cases. In NYC, cases were recruited through hospitals with the largest referral patterns for AA women and controls through random digit dialing (RDD). In NJ, cases were identified in seven counties in NJ thorough the NJ State Cancer Registry, and controls through RDD and community recruitment efforts. In-person interviews were conducted during which questionnaires were administered and detailed anthropometric measurements were taken by trained interviewers. Body composition was assessed by bioelectrical impedance analysis using a Tanita scale. We found little evidence of an association with body mass index (BMI), weight or height. However, both waist and hip circumference were associated with risk in premenopausal women after adjusting for all major known risk factors for breast cancer and BMI, with an OR (95% CI) of 2.52 (1.18-5.39) and 2.54 (1.17-5.50), respectively, comparing highest vs. lowest quartile. For post-menopausal women, the OR was 1.41 (0.71-2.81) for waist circumference and 0.97 (0.48-1.95) for hip circumference. ORs for waist-to-hip ratio were weak and not statistically significant. There was a suggestion of increased risk for higher fat mass and percent body fat after adjusting for BMI and other risk factors in pre-menopausal and post-menopausal women, but confidence intervals included the null. We also evaluated the impact of obesity on clinical presentation at diagnosis among cases. Obese women were diagnosed at a more advanced stage (p<0.01) and with larger tumors at diagnosis (p<0.01). The distributions of grade and ER status were similar among obese and normal BMI women. In conclusion, our study suggests that measures of body fat distribution and body composition (higher waist and hip circumferences, fat mass and percent body fat) are associated with increased breast cancer risk, independent of BMI. Furthermore, while BMI did not appear to affect risk, a higher BMI was associated with more advanced cancer diagnosis among African American women.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 649. doi:1538-7445.AM2012-649