Abstract
Although colorectal cancer death rates in the United States have declined by half since 1970, large geographic disparities persist. Spatial identification of high-risk areas can facilitate targeted screening interventions to close this gap. We used the Getis-Ord Gi* statistic within ArcGIS to identify contemporary colorectal cancer "hotspots" (spatial clusters of counties with high rates) based on county-level mortality data from the national vital statistics system. Hotspots were compared with the remaining aggregated counties (non-hotspot United States) by plotting trends from 1970 to 2011 and calculating rate ratios (RR). Trends were quantified using joinpoint regression. Spatial mapping identified three distinct hotspots in the contemporary United States where colorectal cancer death rates were elevated. The highest rates were in the largest hotspot, which encompassed 94 counties in the Lower Mississippi Delta [Arkansas (17), Illinois (16), Kentucky (3), Louisiana (6), Mississippi (27), Missouri (15), and Tennessee (10)]. During 2009 to 2011, rates here were 40% higher than the non-hotspot United States [RR, 1.40; 95% confidence interval (CI), 1.34-1.46], despite being 18% lower during 1970 to 1972 (RR, 0.82; 95% CI, 0.78-0.86). The elevated risk was similar in blacks and whites. Notably, rates among black men in the Delta increased steadily by 3.5% per year from 1970 to 1990, and have since remained unchanged. Rates in hotspots in west central Appalachia and eastern Virginia/North Carolina were 18% and 9% higher, respectively, than the non-hotspot United States during 2009 to 2011. Advanced spatial analysis revealed large pockets of the United States with excessive colorectal cancer death rates. These well-defined areas warrant prioritized screening intervention.
Highlights
Tremendous progress against colorectal cancer has been achieved in the United States over the past several decades
We considered statistical significance at the confidence level of 95% or higher, associated with P value < 0.05 and Z score > 1.96
By the 2000s, rates were generally homogeneous across the country with the exception of three distinct spatial clusters, or hotspots. These hotspots were located in the Lower Mississippi Delta (Hotspot 1), west central Appalachia (Hotspot 2), and eastern North Carolina/Virginia (Hotspot 3) and included 238 counties in 12 states (Supplementary Table S1)
Summary
Tremendous progress against colorectal cancer has been achieved in the United States over the past several decades. Colorectal cancer death rates have declined by 47% since the mid-1970s [1] This reduction has been attributed to increased population screening (53%), as well as changing patterns in risk factors (35%), and improvements in treatment We previously reported that since the early 1990s, colorectal cancer death rates had declined by !30% in northeastern states, but remained virtually unchanged in Mississippi and Alabama, shifting the burden of disease from the Northeast to the South in little more than a decade [3]. This pattern is consistent with the historical shift in the socioeconomic gradient of colorectal cancer. Spatial identification of high-risk areas can facilitate targeted screening interventions to close this gap
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
