Introduction: Oral cavity squamous cell carcinoma (OSCC) is the most common form of head and neck squamous cell carcinoma (HNSCC) and despite advances in treatment, the 5-year survival rate for HPV-negative HNSCC has only marginally improved over the last five decades. Previous studies have demonstrated Non-Hispanic Black (NHB) patients are more likely to present with higher-stage disease and have higher mortality rates compared to non-Hispanic Whites. In addition, Non-Hispanic Black (NHB) populations are less likely to be screened, in part, due to access to care related to equitable distribution of health care services. There is limited data about oral and dental health care services in urban environments. Based on the hypothesis that OSCC has higher incidence and present at higher stages in regions with less access to dental health care services, we seek to understand the spatial distribution of OSCC prevalence and relate this to the density of dental health care providers.
Methods: We extracted 5-year averages of OSCC incidence and calculated morbidity by zip code for Illinois from 1995 to 2015 using the public dataset from the Illinois Department of Public Health. We merged accessibility factors including median and per-capita income, demographics, educational attainment, poverty rate, urban and rural population distributions, and number of dental health care facility locations. Driving distance to nearest dental facility (ie. screening proxy) was computed and averaged by area. Exploratory spatial data analysis including excess risk calculations, computation of a correlation matrix, associated descriptive statistics, and disease hot spot detection was conducted at state (Illinois) and city (Chicago) scales to identify persistent trends. Because mortality data was not available at zip level, breast and prostate cancer morbidity/mortality rates were added for comparison.
Results: We detected a significant, increasing trend of OSCC in Illinois over our study period (p<0.001) despite a slightly decreasing population trend overall. Hot spots of OSCC incidence were concentrated in the city of Chicago and extended into Chicagoland suburbs and areas in the Southwest corner of the state between 2000 and 2010, with increasing incidence in areas with higher proportions of NHB residents. Eleven zip codes were identified as significant disease clusters in the city of Chicago with an average of 35 cases per area (p=0.008), all located on the South side. A comparison against breast cancer morbidity/mortality suggests that areas of high cancer incidence and dental health care access affect stage of diagnosis.
Conclusion: We demonstrate that OSCC incidence is affected by local dental healthcare access using geospatial maps in a large urban population and state. Using this technique to understand geographic distribution of cancers and treatment access, it is possible to initiate targeted oral screening and education programs can be developed for future study on their impact on reducing disease burden on these high-risk populations.