Background: Gastrointestinal tract cancers are among the most common cancers in Iran and compriseapproximately 38% of all the reported cases of cancer. This study aimed to describe the epidemiology and toinvestigate spatial clustering of common cancers of the gastrointestinal tract across the counties of Iran usingfull Bayesian smoothing and Moran I Index statistics. Materials and
Methods: The data of the national registrycancer were used in this study. Besides, indirect standardized rates were calculated for 371 counties of Iranandsmoothed using Winbug 1.4 software with a full Bayesian method. Global Moran I and local Moran I werealso used to investigate clustering.
Results: According to the results, 75,644 new cases of cancer were nationallyregistered in Iran among which 18,019 cases (23.8%) were esophagus, gastric, colorectal, and liver cancers.The results of Global Moran’s I test were 0.60 (P=0.001), 0.47 (P=0.001), 0.29 (P=0.001), and 0.40 (P=0.001) foresophagus, gastric, colorectal, and liver cancers, respectively. This shows clustering of the four studied cancersin Iran at the national level.
Conclusions: High level clustering of the cases was seen in northern, northwestern,western, and northeastern areas for esophagus, gastric, and colorectal cancers. Considering liver cancer, highclustering was observed in some counties in central, northeastern, and southern areas.