Abstract 5276: Risk factors for ductal carcinoma in situ of the breast in African American women

Abstract

Abstract Introduction: The clinical significance of a ductal carcinoma in situ (DCIS) diagnosis is uncertain. While overall breast cancer mortality risk from DCIS is very low, a recent analysis showed that African American women diagnosed with DCIS were more than twice as likely to die from breast cancer as U.S. white women. Elucidation of risk factors for DCIS in African American women may provide opportunities for risk reduction. Methods: To assess the relation of reproductive, anthropometric, and other factors to risk of DCIS in African American women, we pooled data from three epidemiologic studies participating in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium - the Black Women’s Health Study, the Carolina Breast Cancer Study, and the Women’s Circle of Health Study. These studies contributed 805 DCIS cases and 13,830 controls to the analysis. We used unconditional logistic regression models to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of DCIS in relation to each risk factor of interest. Multivariable models were used to mutually adjust for risk factors as well as matching factors (age, study, geographic region, and questionnaire time period). We also compared results to associations observed for invasive breast cancer (n=3,765). Results: First degree family history of breast cancer was associated with an increased risk of DCIS (OR 1.62, 95% CI 1.32, 1.98). Oral contraceptive use within the past 10 years (vs. never) was also associated with increased risk (OR 1.31, 95% CI 1.01, 1.70), as was late age at first birth (≥25 years vs. <20 years) (OR 1.29, 95% CI 1.04, 1.61). Older age at menarche (≥15 years vs. <11 years) was associated with a reduced risk (OR 0.67, 95% CI 0.49, 0.92). Women with higher body mass index (BMI) in early adulthood (≥25 kg/m2 at ages 18 or 21) had a reduced risk of DCIS compared to those who had a BMI <20 kg/m2 in early adulthood (OR 0.71, 95% CI 0.56, 0.91), but there was no association for current BMI. In general, associations of risk factors for DCIS were similar in magnitude and direction to those for invasive breast cancer. However, high waist-to-hip ratio and absence of breastfeeding, two factors associated with increased risk of invasive breast cancer, and particularly with estrogen receptor negative breast cancer among African American women, were not associated with DCIS, either overall or by estrogen receptor status. Conclusions: Our findings suggest that most risk factors for invasive breast cancer are also risk factors for DCIS among African American women. However, two important modifiable risk factors for invasive breast cancer in this population, higher waist-to-hip ratio and absence of breastfeeding, do not appear to influence DCIS risk. Citation Format: Kimberly A. Bertrand, Traci N. Bethea, Lynn Rosenberg, Elisa V. Bandera, Melissa Troester, Thaer Khoury, Christine B. Ambrosone, Julie R. Palmer. Risk factors for ductal carcinoma in situ of the breast in African American women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5276. doi:10.1158/1538-7445.AM2017-5276