ABSTRACT
<p><b>OBJECTIVE</b>To analyze the geographic spatial patterns and risk areas of main digestive system cancers in Yiwu city.</p><p><b>METHODS</b>Newly diagnosed cases of esophageal, gastric and colorectal cancer during 2010-2014 were obtained from Yiwu Center for Disease Control and Prevention (CDC). The household registration population data in 2013 were obtained from public security bureau. Hierarchy clustering and partitioning regionalization method was used to generate geographic units. Global Moran's I was used to evaluate whether cancer incidence was significantly clustered in space, Anselin Local Moran's I was used to identify statistically significant hot spots, cold spots, and spatial outliers, and Spatial Scan Statistics was implemented to analyze the relative risk of cancers in different areas.</p><p><b>RESULTS</b>The 5-year average incidence of esophageal, gastric and colorectal cancers were 9.99/100 000, 34.01/100 000 and 31.46/100 000, respectively. Males showed significantly higher incidence than females. The incidence was heterogeneous throughout the study area. Spatial Scan analysis revealed that southern Yiwu presented a significantly higher male esophageal cancer (=1.78) and gastric cancer (=1.87) risk. The central area of Yiwu showed a significantly lower female esophageal cancer risk (=0.00) and male stomach cancer risk (=0.63) and the northern Yiwu exhibited a significantly lower female colorectal cancer risk (=0.48).</p><p><b>CONCLUSIONS</b>The incidence of main digestive tract cancers shows a heterogeneous distribution in Yiwu city.</p>
ABSTRACT
Objective Sporadic cases occurring in mall geographic unit could lead to extreme value of incidence due to the small population bases,which would influence the analysis of actual incidence.Methods This study introduced a method of hierarchy clustering and partitioning regionalization,which integrates areas with small population into larger areas with enough population by using Geographic Information System (GIS) based on the principles of spatial continuity and geographical similarity (homogeneity test).This method was applied in spatial epidemiology by using a data set of thyroid cancer incidence in Yiwu,Zhejiang province,between 2010 and 2013.Results Thyroid cancer incidence data were more reliable and stable in the new regionalized areas.Hotspot analysis (Getis-Ord) on the incidence in new areas indicated that there was obvious case clustering in the central area of Yiwu.Conclusion This method can effectively solve the problem of small population base in small geographic units in spatial epidemiological analysis of thyroid cancer incidence and can be used for other diseases and in other areas.