Urban counties in North Carolina have higher overall incidences of breast cancer than rural counties, especially at early stages upon diagnosis, a new analysis shows.

The findings, published in the journal Scientific Reports, serve as a national template for assessing the impact of poor environmental quality across different stages of breast cancer, which is marked by highly diverse origins and mechanisms for spreading.

North Carolina serves as a good model; it has a diverse population of 10 million spread over 100 rural and urban counties with varying environmental conditions.

“Individual environmental contaminants have long been associated with breast cancer, but we have limited understanding of how multiple exposures simultaneously affect this disease,” says senior author Gayathri Devi, a professor in the departments of surgery and pathology at Duke University 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 Environmental Quality Index (EQI)—a county-by-county assessment of air, water, land, built environment, as well as the sociodemographic environment,” Devi says. “This type of data analysis allows for a high-level look at broader environmental factors and health outcomes.”

Devi and colleagues, including lead author Larisa M. Gearhart-Serna, who steered the research as a PhD candidate at Duke, analyzed the EQI data alongside breast cancer incidence rates from the North Carolina Central Cancer Registry. The team further evaluated the different breast cancer stages—in situ and localized (early stages), regional and distant (later stages)—stratified by rural-urban status.

“In an earlier study, we assessed how environmental conditions impact the risk of a breast cancer patient having later stage invasive disease compared to non-invasive carcinoma in-situ,” Gearhart-Serna says. “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.”

In counties with poor overall environmental quality compared to those with good environmental quality, total breast cancer incidence was higher by 10.82 cases per 100,000 persons. This association was most pronounced for localized breast cancer.

Read the full article about breast cancer rates by Sarah Avery at Futurity.