Overcoming Small Numbers in a Small State: Vermont’s Approach to Cancer Mapping – 1/3/2014

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Speakers: Jennifer Kachajian, MA, MPH

Objectives:Description: Concerns are raised routinely by individuals regarding the number of cancers in their communities. There has been a need to evaluate how the number of cases observed in a community compares with the number expected. However, Vermont’s small number of cases and population present challenges for community-level analysis. Several approaches to standardized incidence ratio (SIR) calculation and web-based mapping were evaluated. Existing methodology did not meet our need to correct for multiple comparisons or being easy to use. The Vermont Cancer Registry geocoded the 2001-2008 diagnosis years using ESRI ArcGIS. Standardized Incidence Ratios (SIR’s) were computed at the community level, using the false discovery rate (FDR) method for multiple comparisons. Consensus on methodology was reached among statisticians, cancer registry personnel, department leadership, and the Environmental Public Health Tracking (EPHT) Program. Data are displayed using Instant Atlas. Vermont has found that it is possible to address small number limitations and display data at the community level, without going to very large geographies (i.e., counties). Future uses of this methodology include VCR’s updating of the SIR’s with more current data and other surveillance programs using the community-level geographies for data reporting and use.

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