Abstract D097: Association between high mammographic density and environmental chromium and arsenic exposure in a pilot study of women living in rural communities
Authors: Su L. Joseph , Chiang Tung-Chin , Rogers Lora J , Runnells Gail A , Kadlubar Susan A , Crystal Zoey , Wardell Christopher , Malak Sharp 
Published: September 2020

Abstract
Background Environmental contamination with heavy metals, such as metalloid arsenic (As), cadmium (Cd), and chromium (Cr), in soil in the Mississippi River Delta region has been documented by the US Geological Survey. Rural residents are more likely to be exposed throughout their life than those who live in urban cities because much of the vegetation grown in this area has a potentially higher content of these heavy metals. At the same time, this region also experiences higher breast cancer (BC) disparity when compared to the other parts of the country. Mammographic density (MD) is one of the strongest risk factors for nonfamilial BC and it is also related to long-term prospective increases in tumor incidence, independent of its masking effects on detection. High MD thus is directly related to breast carcinogenesis. Methods Urine samples and lifestyle factors were obtained from a subcohort of women recruited through a mobile mammography unit into the Arkansas Rural Community Health Study cohort. Mammography at enrollment is available on everyone in this subcohort. Urinary samples were analyzed for heavy metal exposure, including As, Cd, and Cr concentration using Fisher-Thermo inductively coupled plasma mass spectrometry (ICP-MS). All samples were analyzed in duplicates and concentrations were presented as microgram/gram creatinine. Mammographic density was assessed by staff radiologist based on the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) and verified with the LIBRA software, developed by the University of Pennsylvania. MD was categorized as dichotomous high (C and D) and low (A and B). Multivariable logistic regression was used to calculate odds ratios (OR) and 95% confidence interval (CI). Results Among 189 subjects who have completed follow-up interviews and contributed blood and urine samples, wee analyzed urine samples for heavy metal concentration, adjusted for urinary creatinine value and specific gravity. The mean (standard deviation) concentration of Cr, As and Cd were 0.27 (0.04), 0.28 (0.38) and 0.13 (0.11) ppb, respectively. We evaluated the association between MD and three major heavy metals of interest. When comparing the highest tertile urine Cr to the lowest tertile, Cr is positively associated with high MD (OR = 5.50, 95%CI = 1.08, 27.98) after adjusting for age, BMI, race, education, hormonal use, age at menarche, age at last menstrual cycle, and family history of breast cancer. Urine As is also positively associated with high MD (OR = 2.39, 95%CI = 0.98, 5.87, p = 0.06), adjusted for age and BMI. Cd was not significantly associated with MD with the current sample size. Conclusion Cr, As, and Cd are considered as Group 1 carcinogens according to the International Agency for Research on Cancer. This study suggests that there is a significantly increased odds of high MD even at very low levels of exposure to environmental Cr and As. Identifying sources of these contaminants would reduce the risk of breast cancer in rural communities.
Citation Format: L. Joseph Su, Tung-Chin Chiang, Lora J Rogers, Gail A Runnells, Susan A Kadlubar, Zoey Crystal, Christopher Wardell, Sharp Malak. Association between high mammographic density and environmental chromium and arsenic exposure in a pilot study of women living in rural communities [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 D097.