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Characteristics of mammography facility locations and stage of breast cancer at diagnosis in Chicago.

In the United States, despite substantial investment in public health initiatives to promote early detection of breast cancer through screening mammography, the proportion of female breast cancers that have advanced beyond the localized stage by the time of diagnosis remains high. Our objective in this exploratory study was to investigate whether stage of breast cancer at diagnosis among Chicago residents is associated with characteristics of the neighborhoods in which proximate mammography facilities are located. Those characteristics may influence likelihood of utilizing the service routinely and partly explain differences in stage at diagnosis. We used a retrospective cohort design and combined 3 years of data from the Illinois State Cancer Registry (ISCR) with information on locations of mammography facilities, public transportation service, crime, and area demographic and economic characteristics. Using a Geographic Information System (GIS), we identified the five facilities located nearest to each case's residence. Estimates of the association between characteristics of mammography facility locations and breast cancer stage at diagnosis were obtained using the partial proportional odds regression model. We found that the number of homicides in areas in which the nearest mammography facilities were located was associated with increased odds of later stage diagnosis. This effect was independent of age, race, and residential area education and income. We found no effect on stage of distance, public transportation service, or measures of neighborhood social similarity. The "spatial dynamics" of health may involve geographies beyond the immediate neighborhood. The results of our study suggest that areas in which the nearest mammography facilities are located may be one such geography. We hope that this study will spark research interest in the impact of health service locations on utilization.