Bayesian spatio-temporal analysis of stomach cancer incidence in Iran, 2003-2010

Stomach cancer is the second most common cancer in Iranian men and the fourth most common cancer in Iranian women. The incidence rate of this cancer in Iranian men is almost 2.5 times that in women. The objective of this study was to investigate the trend of stomach cancer incidence rate in Iran in an 8-year time period (2003-2010) and also update the incidence estimates of stomach cancer. Data from a total number of 41,830 patients diagnosed with stomach cancer according to the International Classification of Diseases (C16) in 2003-2010 were analyzed. We used Bayesian spatial and Bayesian spatio-temporal models to study the relative risk and trend of stomach cancer incidence rate in Iran. Out of 41,830 stomach cancer registered patients, 72% were male. The average smoothed SIRs were 0.79, 0.82 and 0.78 for the general, female and male population, respectively. This shows a nearly stable incidence rate. The northwest of Iran had the highest incidence rate of stomach cancer. The trend of this rate was declining to the lowest rate in the southeast of the country. The estimated values of coefficient of the trend term for general, female and male population in this model were 0.0085, - 0.018 and 0.0041, which indicate almost a stable fixed trend. The map of temporal trends also showed that although the incidence rate of this cancer is to some extent stable, in general, in the central and in the east of the country the incidence relative risk has increased over time. The prevalence of Helicobacter pylori infection, Lower socioeconomic status and Iodine deficiency were speculated to be relevant factors for the high incidence rates of stomach cancer in the northwest of Iran. Preventive measures in the north and northwest of Iran could have an effect on controlling this cancer in these areas.