Development of Sub-County Cancer Reporting Zones in Delaware and Example Use Case for Targeted Interventions.

Objective: To describe the Delaware Cancer Registry (DCR)'s participation in the National Cancer Institute (NCI)/North American Association of Central Cancer Registries (NAACCR) Zone Design Project to create sub-county geographic areas ("zones") for use in cancer reporting and geospatial analysis.

Methods: DCR and other stakeholders reviewed up to ten unique zone configurations for each of Delaware's three counties. The zone configurations were created using AZTool and were set to optimize three objectives: create zones that have a minimum and target population of 50,000; are homogenous based on the variables of percent minority, percent below poverty, and percent urban; and are as compact as possible. The DCR sent a survey to stakeholders to provide input on their preferred zone configuration for each county. Following the final selection of zones, the DCR utilized the geographies for calculating overall and late-stage breast cancer incidence statistics and created choropleth maps to visualize the rates by quintiles.

Results: The final selections resulted in a total of 15 zones for Delaware, with three in Kent County, nine in New Castle County, and three in Sussex County. The zones ranged in population size from 54,013 to 67,693 people. Zones with higher late-stage breast cancer incidence rates included those near the areas of Wilmington, Middletown, and between Milford and Georgetown. Comparing results of overall breast cancer incidence rates by zone with late-stage rates by zone, there were areas that had lower relative overall breast cancer incidence rates but were relatively higher for late-stage rates by zones or vice versa.

Conclusions: Aggregating census tracts into zones allows for reporting reliable cancer rates at sub-county levels, which is instrumental in conveying meaningful information about regional cancer trends to stakeholders and the public. Delaware will be able to utilize zone-level cancer information to provide targeted interventions and outreach initiatives.