County-level characteristics associated with incidence, late-stage incidence, and mortality from screenable cancers

Background: Cancer screening differs by rurality and racial residential segregation, but the relationship between these county-level characteristics is understudied. Understanding this relationship and its implications for cancer outcomes could inform interventions to decrease cancer disparities. Methods: We linked county-level information from national data sources: 2008-2012 cancer incidence, late-stage incidence, and mortality rates (for breast, cervical, and colorectal cancer) from U.S. Cancer Statistics and the National Death Index; metropolitan status from U.S. Department of Agriculture; residential segregation derived from American Community Survey; and prevalence of cancer screening from National Cancer Institute's Small Area Estimates. We used multivariable, sparse Poisson generalized linear mixed models to assess cancer incidence, late-stage incidence, and mortality rates by county-level characteristics, controlling for density of physicians and median household income. Results: Cancer incidence, late-stage incidence, and mortality rates were 6-18% lower in metropolitan counties for breast and colorectal cancer, and 2-4% lower in more segregated counties for breast and colorectal cancer. Generally, reductions in cancer associated with residential segregation were limited to non-metropolitan counties. Cancer incidence, late-stage incidence, and mortality rates were associated with screening, with rates for corresponding cancers that were 2-9% higher in areas with more breast and colorectal screening, but 2-15% lower in areas with more cervical screening. Discussion: Lower cancer burden was observed in counties that were metropolitan and more segregated. Effect modification was observed by metropolitan status and county-level residential segregation, indicating that residential segregation may impact healthcare access differently in different county types. Additional studies are needed to inform interventions to reduce county-level disparities in cancer incidence, late-stage incidence, and mortality.