Abstract C075: Association of obesity with breast cancer subtypes among non-Hispanic Black women
Authors: Moore Jaleesa , Sanderson Maureen , Pal Tuya , Fadden Mary Kay , Dujon Steffie-Ann , Reid Sonya , Tezak Anne , Lipworth Loren 
Published: September 2020

Abstract
Although non-Hispanic White and non-Hispanic Black women have similar breast cancer incidence rates, Black women are more likely to be diagnosed with aggressive or late-stage disease and have higher mortality rates compared to White women. Clinical studies have demonstrated that tumors lacking estrogen receptor (ER), progesterone receptor (PR) and/or human epidermal growth factor receptor 2 (HER2) (referred to as “triple negative breast cancers” or TNBC), are associated with an aggressive pathology and poor prognosis and distinct risk factor profiles, compared to those with receptor positivity. Through the current study, we examined the effect of obesity in the development of breast cancer subtypes; specifically, ER- tumors and TNBC. To examine the association between body mass index (BMI) and breast cancer subtype, we utilized a pooled dataset of Black women with breast cancer from four studies: Black Women Etiology and Survival of Triple-negative Breast Cancers Study, Southern Community Cohort Study, Nashville Breast Health Study and the Tri-State Breast Study. For all four studies, information on tumor ER, PR and HER2 status was abstracted from state cancer registry records and supplemented by available pathology reports and medical records. We calculated BMI as kg/m2, based on self-reported weight and height, and classified it as normal (18.5-&lt;25), overweight (25-&lt;30), obese I (30-&lt;35), obese II (35-&lt;40) and obese III (40+). Case-only logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between obesity and breast cancer subtype, using ER+ as the reference group for ER- and TNBC. Since the association between obesity and breast cancer has been shown to differ between pre- and postmenopausal women, all analyses were stratified by menopausal status at breast cancer diagnosis. Approximately 70% of the 2,801 women included in the study were postmenopausal at breast cancer diagnosis. Overall, 69% of the tumors were ER+, with similar proportions among pre- and post-menopausal women. In total, 25% were TNBC, of which a third were among pre-menopausal patients. In multivariable analyses, using premenopausal women with ER+ breast cancer as the reference group, those with ER- breast cancer (OR 2.16, 95% CI 1.20-3.88) or TNBC (OR 2.13, 95% CI 1.06-4.28) were more likely to be in the obese II category. Among postmenopausal women, there was no clear association between obesity and breast cancer subtype, although the obese class I category was non-significantly associated with lower risk of TNBC compared to ER+ subtype (OR 0.79, 95% CI 0.53-1.17). Our study represents one of the largest studies to assess the differential impact of obesity on breast cancer subtypes among Black women. Our findings suggest that higher BMI is associated with increased risk of TNBC for premenopausal women and demonstrates that premenopausal obese Black women are more likely to be diagnosed with ER- and TNBC compared with ER+ tumors.
Citation Format: Jaleesa Moore, Maureen Sanderson, Tuya Pal, Mary Kay Fadden, Steffie-Ann Dujon, Sonya Reid, Anne Tezak, Loren Lipworth. Association of obesity with breast cancer subtypes among non-Hispanic Black women [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C075.