Freeman VL, et al. – For calculating age–standardized cancer incidence rates in non–census defined geographical areas using publically available data, a geographic information system–based method was described. In non–census defined geographies, areal interpolation through dasymetric mapping could estimate cancer rates. It had the potential to address gaps in local cancer–related health data, inform health resource advocacy, and guide community–centered cancer prevention and control.

Methods

• From the Illinois State Cancer Registry, aggregated records of cancer cases diagnosed from 2009 through 2013 in each of Chicago’s 77 census-defined community areas were obtained.
• Experts used areal interpolation through dasymetric mapping of census blocks to redistribute populations and case counts from community areas to Chicago’s 50 politically defined aldermanic wards.
• In addition, ward-level age-standardized 5-year cumulative incidence rates were calculated.

Results

• As per observations, potential errors in redistributing populations between geographies were limited to ≤1.5% of the total population, and agreement between the ward population estimates and those from a frequently cited reference set of estimates was high (Pearson correlation r = 0.99, mean difference = -4 persons).
• In addition, a map overlay of safety-net primary care clinic locations and ward-level incidence rates for advanced-staged cancers revealed potential pathways for prevention.