Non-random geographic distribution of patients with cutaneous T-cell lymphoma in the Greater Pittsburgh Area
Abstract
Background: Environmental hazards may play a role in the etiology of cutaneous T-cell lymphoma (CTCL). Some studies have found an increased incidence of CTCL among workers in chemical science, transportation, and manufacturing industries, but other studies have not. This discrepancy may be attributable to population migration, complicating accurate assessment of lifetime exposures. The Pittsburgh population has very low migration rates and most CTCL patients seen at the University of Pittsburgh Medical Center (UPMC) Cutaneous Lymphoma Center are life-long local residents. The Greater Pittsburgh Area used to be an industrial hub. There are residential communities positioned within close proximity to inactive industrial sites that continue to contain pollutants.
Objective: To determine whether CTCL patients’ residences cluster within specific Pittsburgh regions, in particular, those with high levels of environmental pollutants.
Methods: Our study included patients diagnosed with CTCL at the UPMC Cutaneous Lymphoma Center between 2000 and 2012. We mapped the longitudinal and latitudinal coordinates of patients’ residences at diagnosis, superfund sites, toxic release inventory sites, particular matter levels, and dermatologists’ offices using ArcMap 10.1. We then performed a SaTScan analysis using zip codes to assess for geographic clustering of patients’ residences in the Pittsburgh metropolitan statistical area. We assessed for a correlation between case distribution and both environmental hazards sites and dermatologist density in the area.
Results: We identified 274 patients with CTCL in the Greater Pittsburgh area. We identified a statistically significant geographic cluster (p<.001) in zip code 15213, which is the most densely populated neighborhood in Pittsburgh and the site of the region’s only CTCL clinic. We observed no relationship between the locations of superfund sites, toxic release inventory sites, or particular matter levels and CTCL case distribution.
Conclusion: Our findings do not support an association between exposure to environmental toxins and CTCL. CTCL cases clustered in areas with the highest population density, which also happen to include a regional CTCL center. To evaluate a possibility of urban pollutants playing a role in etiology of CTCL, dermatologist density and access to care need to be addressed as potential confounders in the future studies.