Background: Oesophageal cancer (OC) is the fourth leading cause of cancer death in China. This study aims to examine the geographic spread of OC mortality in two periods in a large Chinese population.
Methods: Age-standardised mortality rates (ASMRs) for 140 county-level units in Shandong Province during the periods 1970-1974 and 2011-2013 were calculated using death data from the First National Cause-of-Death Survey and the Shandong Death Registration System, respectively. Mortality estimates were smoothed using Area-to-Area Poisson kriging techniques, and spatial clusters in each time period were detected using spatial scan statistics method.
Results: The provincial average ASMR decreased from 13.0 per 100,000 in 1970-1974 to 5.8 per 100,000 in 2010-2013. Almost all the areas have experienced a decrease in OC mortality, while the reduction was particularly pronounced in the mid-west region. This study has identified a geographical cluster with very high EC mortality in each period. Residents living in the cluster during 1970-74 were 2.7 (95% CI: 2.2-3.4) times more likely to die from EC than the rest of the province. The corresponding risk ratio for the 2011-13 cluster was 3.7 (95% CI: 2.8-5.0). The clustering pattern has largely unchanged over the past 40 years.
Conclusions: This study detected a geographically defined subpopulation in Shandong, China with much higher risk of dying from OC. This spatial pattern was consistently observed in two time periods about 40 years apart. The results suggest the key drivers for geographic variation in esophageal cancer may not have changed.