Abstract 4217: Cumulative environmental quality is associated with breast cancer incidence differentially by summary stage and urbanicity
Authors: Gearhart-Serna Larisa M. , Hoffman Kate , Hsu Hillary , Devi Gayathri R. 
Published: April 2023

Individual environmental contaminants have been associated with breast cancer (BCa); however, simultaneous evaluations of multiple exposures are limited. The USEPA has constructed an environmental quality index (EQI) that includes different exposures across air, water, land, sociodemographic, and built environments. As links between BCa and the EQI have so far been confined to total BCa incidence, herein we investigated if these multiple exposures in broad EQI domains were associated with BCa incidence stratified by stage of disease.

Incidence rates of total, in situ, localized, regional, and distant breast cancer were assessed by linking the EQI dataset to county-level age-standardized incidence rates obtained from the North Carolina Central Cancer Registry (2010-2014), which reports all cancer cases diagnosed in NC residents. Generalized linear models (SAS 9.3) were constructed to determine the associations between breast cancer incidence rates by summary stage and the EQI in total and by domain, compared across rural versus urban counties. Models were adjusted for percent African American (AA), percent smokers, and mammography screening rates in each county. Mann-Whitney rank tests and D'Agostino-Pearson normality tests were used to determine statistical significance.

Results showed that the EQI is variable across NC, akin to variability across the U.S. (interquartile range 25th-75th% for total EQI in NC: -0.187 to 0.734 vs in the U.S.: –0.606 to 0.706). In counties with poor total EQI scores, and thus poor overall environmental quality, total BCa incidence increased by 10.82 cases per 100,000 persons (95%CI: 2.04, 19.60, p=0.016). This association was most pronounced for localized BCa (β=5.59, 95%CI: 0.59, 10.58, p=0.029). Higher incidence of early-stage disease (carcinoma in situ β=5.25, 95%CI: 2.34, 8.16, p=0.001 and localized BCa β=6.98, 95%CI: 2.24, 11.73, p=0.004) and total breast cancer (β=11.44, 95%CI: 3.01, 19.87, p=0.008) also occurred in counties with poor land quality, especially urban counties. The county AA percentage was associated with increased incidence of regional (0.12 cases per % increase, 95% CI 0.01, 0.22, p=0.022) and distant BCa (0.06 per % increase, 95% CI 0.02, 0.10, p=0.003). Associations persisted and were strengthened in urban counties for regional BCa, and in rural counties for distant BCa.

In sum, we found that BCa is associated with environmental quality differentially by disease stage, environmental domain, and urbanicity. Although what drives poor EQI varies by region, our analyses are generalizable to other states and counties across the U.S. and suggest that cumulative environmental exposures should be assessed in the context of cancer stage. Funding: Duke Cancer Institute pilot (GRD, KPH) in P30 Cancer Ctr grant; NIEHS T32-ESO21432-05; NCI-3P20CA202925-04S2 Diversity Supplement (LGS).

Citation Format: Larisa M. Gearhart-Serna, Kate Hoffman, Hillary Hsu, Gayathri R. Devi. Cumulative environmental quality is associated with breast cancer incidence differentially by summary stage and urbanicity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4217.