AACR Environmental Carcinogenesis: Study Finds Environmental Quality Linked With Distant/Metastatic Breast Cancer Risk
Although many risk factors increase a woman’s chance of developing breast cancer—including genetic and hormonal causes—there is increasing evidence suggesting an environmental link. A study investigating the effects of the cumulative environmental quality on aggressive breast cancers in North Carolina has found that patients living in a county with the worst land environmental quality were 5% more likely to be diagnosed with distant/metastatic breast cancer than ductal carcinoma in situ (DCIS). Socioeconomic status also impacted the type of breast cancer diagnosis—those with a higher income were less likely to be diagnosed with distant/metastatic breast cancer. The study by Gearhart-Serna et al is being presented at the American Association for Cancer Research (AACR) conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention.
Study Methods
Researchers from Duke University hypothesized that environmental quality plays a role in the development of aggressive breast cancers and that these effects vary by rural and urban communities. To test their theory, the investigators compared the odds of having distant/metastatic breast cancer vs DCIS based on total and domain-specific environmental quality index values generated by the U.S. Environmental Protection Agency. They collected data from patients with breast cancer from the North Carolina Central Cancer Registry for the years 2009–2014 and based on staging criteria from the Surveillance, Epidemiology, and End Results Program.
The researchers used generalized estimating equation models to generate odds ratios for having distant/metastatic breast cancer using patients with DCIS as controls and quartile environmental quality index domain values adjusted for age, body mass index, and smoking history. They also stratified patients into rural and urban categories based on their county at diagnosis, representing more urbanized to more thinly populated areas of the state.
Results
The researchers found that patients residing in a county with the worst land environmental quality were 5% more likely to have distant/metastatic breast cancer than DCIS (odds ratio [OR] = 1.05, 95% confidence interval [CI] = 1.01–1.09; P = .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.
In addition, 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 = .0006), which was consistent across rural and urban areas.
Within the sociodemographic domain, higher income and higher household value decreased the odds of having distant/metastatic breast cancer, regardless of whether the area was rural or urban.
Need for Further Research
“We have shown that cumulative environmental quality is associated with distant/metastatic breast cancer, and that these effects can differ by rural [or] urban area. This is relevant for further studies of environmental exposures associated with aggressive breast cancers,” concluded the study authors.
Disclosure: For full disclosures of the study authors, visit aacr.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
