Breast cancer is a complex and multifactorial disease, and there is increasing evidence of association between breast cancer incidence and environmental factors. This study sought to investigate the effects of cumulative environmental quality on aggressive breast cancer in North Carolina. We hypothesized that environmental quality plays a role in aggressive breast cancer incidence, and additionally that these effects vary by rural-urban context. The USEPA generates an environmental quality index (EQI), which contains county-level data on environmental quality across five domains—air, water, land, sociodemographic, and built. To address our hypothesis, we compared the odds of having distant/metastatic breast cancer versus ductal carcinoma in situ (DCIS) based on total and domain-specific EQI values, with cancer case information extracted from the North Carolina Central Cancer Registry (years 2009-2014) and based on staging criteria from the Surveillance, Epidemiology, and End Results Program (SEER). We used generalized estimating equation (GEE) models to generate odds ratios for having distant/metastatic breast cancer using DCIS patients as controls and quartiled EQI domain values, adjusting for individual age, BMI, and smoking status. We also stratified patients into rural-urban categories based on their county at diagnosis, representing more urbanized to more thinly populated areas. Each EQI domain is composed of several individual environmental factors, so we then investigated which of these individual factors were driving domain specific effects. Results show that there is an effect of environmental quality on distant/metastatic breast cancer. For example, patients residing in a county with the worst land environmental quality were 5% more likely to have distant/metastatic breast cancer than DCIS (OR 1.05, 95% CI 1.01-1.09, p=0.0063). This effect was stronger in more rural areas. Within the land domain, higher use of agricultural chemicals such as herbicides and insecticides had effects on increased distant/metastatic breast cancer incidence in more urban areas, whereas the number of animal facilities had a large effect in more rural areas. Additionally, patients residing in a county with the worst sociodemographic environmental quality were 6% more likely to have distant/metastatic breast cancer than DCIS (OR 1.06, 95% CI 1.02-1.09, p=0.0006), which was consistent across rural/urban areas. Within the sociodemographic domain, higher income and higher household value decreased odds of having distant/metastatic breast cancer regardless of whether the area was rural or urban. In conclusion, we have shown that cumulative environmental quality is associated with distant/metastatic breast cancer, and that these effects can differ by rural-urban area. This is relevant for further studies of environmental exposures associated with aggressive breast cancers.

This abstract is also being presented as Poster A07.

Citation Format: Larisa M. Gearhart-Serna, Kate Hoffman, Brittany A. Mills, Gayathri R. Devi. North Carolina environmental quality is associated with distant/metastatic breast cancer: Evidence for rural-urban disparities [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr PR06.