Geographical Mapping of Biological and Environmental Risk Factors of Colorectal Cancer in the United States

PURPOSE Colorectal cancer (CRC) is a leading cause of morbidity and mortality in the United States (US) and worldwide. Previous studies have identified several behavioral and biological risk factors of CRC, including lack of physical activity, smoking, alcohol use, poor dietary patterns, obesity and type 2 diabetes. Emerging risk factors, e.g., air pollution and pesticide exposure may also exacerbate colorectal cancer risk. Furthermore, rural populations show poorer CRC outcomes compared to urban ones within the US. METHODS In order to quantitatively assess this, we examined publicly available US county-level CRC incidence and mortality data from the Surveillance, Epidemiology and End Results (SEER) program and risk factor prevalence data from Behavioral Risk Factor Surveillance System (BRFSS) to identify geographical patterns and interactions of colorectal cancer risk factors by applying simple and multiple linear regression modeling as well as machine learning. RESULTS Our analyses indicated that multiple risk factors were strongly correlated with CRC and co-occurred in counties with high CRC incidence and mortality, e.g, obesity, diabetes, smoking and low physical activity. Stratifying data by urban and rural counties showed differences in how these factors contributed to CRC risk. CONCLUSION Identifying etiological factors driving these co-occurrence trends and examining additional CRC risk factors will therefore be critical components of future CRC risk identification and risk mitigation effort.