Spatial Analysis of Esophageal Cancer Mortality in a High-risk Population in China: Consistent Clustering Pattern in 1970-74 and 2011-13

Abstract

Purpose: Almost half of the global esophageal cancer (EC) deaths occurred in China. This study aims to examine<br />the geographic spread of EC mortality in two periods in a large Chinese population. Methods: Age-standardized<br />mortality rates (ASMRs) for 140 county-level units in Shandong Province during the periods 1970-74 and 2011-13<br />were derived using data from the First National Cause-of-Death Survey and the Shandong Death Registration System,<br />respectively. ASMRs were smoothed using Area-to-Area Poisson kriging technique. Spatial scan statistics were used to<br />detect spatial clusters with higher EC mortality and clusters with greater temporal changes in EC mortality. Results:<br />The provincial average ASMR decreased from 13.0 per 100,000 in 1970-74 to 5.8 in 2010-13. Almost all counties or<br />districts have experienced a decrease in EC mortality, while the reduction was particularly pronounced in the mid-west<br />region. This study has identified a geographical cluster with much higher EC mortality rates and the clustering pattern<br />has largely unchanged over the past 40 years. Residents living in the cluster during 1970-74 were 2.7 (95% CI: 2.2-3.4)<br />times more likely to die from EC than the rest of the province. The corresponding risk ratio for the 2011-13 cluster was<br />3.7 (95% CI: 2.8-5.0). Conclusions: This study detected a geographically defined subpopulation in Shandong, China<br />with much higher risk of dying from EC. This spatial pattern has been consistent over the past few decades. The results<br />suggest the key drives for geographic variations in esophageal cancer may not have changed.