Abstract D096: Disparities in toxic heavy metal burden and breast cancer risk: Findings from the Metropolitan Chicago Breast Cancer Registry
Authors: Kaushiva Alpana , Kresovich Jacob , Erdal Serap , Rauscher Garth 
Published: September 2020

Abstract
BACKGROUND: Evidence regarding associations of ambient toxic heavy metals (THMs) and breast cancer (BC) incidence is mixed. Observed inconsistencies may be a consequence of utilizing ambient THM levels collected close to time of BC diagnosis, and not incorporating an appropriate latent period. In addition, most studies have not examined associations of ambient THMs and BC incidence stratified by estrogen receptor (ER) and menopausal status, and have examined relatively homogenous populations of non-Hispanic White (nHW) women. We examined time-to-event associations of ambient THM concentrations and BC subtypes among women enrolled in the racially/ethnically diverse Metropolitan Chicago Breast Cancer Registry (MCBCR) cohort. METHODS: Using the Environmental Protection Agency’s 2005 National Air Toxics Assessment (NATA), we examined census tract-level ambient concentrations for 11 THMs (antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium). For women enrolled in MCBCR between 2003-2007, residential addresses were geocoded and matched to census-tract estimates of the ambient THM concentrations. Women were followed to time of BC diagnosis or December 31, 2014. Cox proportional hazards (PH) regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI), adjusted for age and race. RESULTS: Over a mean follow up time of 10 years, there were 6,579 incident BC cases (with a mean time to diagnosis of 3 years) and 205,095 cancer-free women in the cohort. Over a quarter of our study population was African American (AA), and nearly 10% were Hispanic. Compared to nHW women, AA women were more likely to reside in census tracts with higher quartile ambient concentrations of beryllium, cadmium, chromium, cobalt, lead, manganese, and mercury (p&lt;0.001 for all). Similarly, Hispanic women were more likely to reside in census tracts characterized by higher quartile oncentrations of beryllium, cadmium, chromium, lead, manganese, mercury, and nickel (p&lt;0.001 for all). In age and race adjusted models, compared to women residing in census tracts with the lowest quartile of ambient concentrations, increased BC incidence was observed for women residing in census tracts with the highest quartile of ambient concentrations of antimony (HR=1.08, 95% CI 1.00-1.17), beryllium (HR=1.09, 95% CI 1.01-1.18), cadmium (HR=1.07, 95% CI 1.00-1.17), lead (HR=1.18, 95% CI 1.09, 1.28), and nickel (HR=1.24, 95% CI 1.15-1.33). In models stratified by ER status and menopausal status, associations with beryllium, lead, and nickel were stronger for ER positive post-menopausal BC. Associations with antimony and cadmium were stronger for ER-negative BC risk. DISCUSSION: We found that African American and Hispanic women were disproportionately exposed to higher levels of ambient THMs, which in turn were associated with specific subtypes of BC. Future studies will focus on determinants of these observed environmental disparities in the MCBCR cohort.
Citation Format: Alpana Kaushiva, Jacob Kresovich, Serap Erdal, Garth Rauscher. Disparities in toxic heavy metal burden and breast cancer risk: Findings from the Metropolitan Chicago Breast Cancer Registry [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 D096.