Investigators have uncovered that North Carolina’s urban counties may have higher overall incidences of breast cancer than its rural counties, especially at early stages at diagnosis, according to a recent study published by Gearhart-Serna et al in Scientific Reports. These findings may serve as a national template for assessing the impact of poor environmental quality across different stages of breast cancer.
Background
Breast cancer is marked by highly diverse origins and mechanisms of metastasis.
The Environmental Quality Index (EQI) is a county-by-county assessment of air, water, land, built environment, as well as the sociodemographic environment.
“Individual environmental contaminants have long been associated with breast cancer, but we have [a] limited understanding of how multiple exposures simultaneously affect this disease,” explained senior study author Gayathri Devi, PhD, Professor in the Departments of Surgery and Pathology at the Duke University School of Medicine and Program Director of the Duke Consortium for Inflammatory Breast Cancer at the Duke Cancer Institute. “Our study explored the incidence of breast cancer within the context of the EQI. This type of data analysis allows for a high-level look at broader environmental factors and health outcomes,” she highlighted.
“In an earlier study, we assessed how environmental conditions impact the risk of a [patient with] breast cancer having later-stage invasive disease compared to noninvasive carcinoma in situ,” detailed lead study author Larisa M. Gearhart-Serna, PhD, MBA, who steered the research as a PhD candidate at the Duke University School of Medicine. “This is a continuation of that work to determine whether environmental quality and an urban environment are related to the development of more advanced tumors in a community and, if so, what stages,” she added.
Study Methods and Results
In this study, the investigators used the North Carolina Central Cancer Registry to analyze the EQI data and breast cancer incidence rates in individuals residing in North Carolina. The investigators further evaluated the different breast cancer stages stratified by rural or urban status.
Because North Carolina has a diverse population of 10 million individuals spread over 100 rural and urban counties, with varying environmental conditions, the investigators noted the state served as an effective model.
Compared with the counties that had a good environmental quality, the investigators found the counties with a poor overall environmental quality had a total breast cancer incidence that was higher by 10.82 cases per 100,000 individuals. This association was most pronounced for localized breast cancer.
Additionally, the investigators discovered the community-level effects of environmental exposures—notably in counties with poor land quality caused by pesticides and toxic releases from industrial, agricultural, and animal facilities—were correlated with higher rates of total breast cancer incidence, especially in urban settings.
The investigators revealed the breast cancer incidence rates were also higher for later-stage disease and total breast cancer among counties with higher populations of Black individuals. They suggested these findings may be relevant, since the global incidence of aggressive breast cancer is higher in Black women.
Further, higher mammography screening rates were linked to lower regional breast cancer incidence rates. The investigators emphasized that improved screening may decrease diagnoses of later-stage breast cancer.
Conclusions
“Our analyses indicate significant associations between environmental quality and breast cancer incidence—which differ by breast cancer stage and urbanicity—identifying a critical need to assess cumulative environmental exposures in the context of cancer stage,” Dr. Gearhart-Serna underscored. “This has the potential to develop measures to reduce disease incidence in vulnerable communities,” she concluded.
Disclosure: The research in this study was funded in part by the National Institutes of Health, the National Cancer Institute, and the National Institute of Environmental Health Sciences. For full disclosures of the study authors, visit nature.com.
