Geographical spread of gastrointestinal tract cancer incidence in the Caspian Sea region of Iran: Spatial analysis of cancer registry data

The Babol Cancer Registry, which covers the two major northern Iranian provinces of Mazandaran and Golestan (total population = 4,484,622) was used to identify new gastrointestinal tract cancer cases during 2001 to 2005. Age-specific cancer incidence rates were calculated for 7 gastrointestinal tract cancer sites in 26 wards of the Mazandaran and Golestan provinces. Spatial autocorrelation indices, hierarchical Bayesian Poisson models, and spatial scan statistics were used in measuring the geographic pattern and clusters.There were non-random spatial patterns in esophageal and stomach cancers that were similar for both sexes. Clusters of high incidence were identified in esophageal, stomach, colorectal and liver cancer for both sexes, as well as a possible cluster of pancreas cancer in males.Gastrointestinal tract cancers exhibit significant spatial clustering of risk in northern Iran. Further work is needed to relate these geographical patterns to information on potential life-style and environmental factors.Approximately 50,000 new cases of cancer occur each year in the Iranian population of 70.4 million. The most common organ system involved with more than 38% of all cancers is the gastrointestinal (GI) tract. Stomach, esophagus, and colorectal are the three most common cancers in males; in females, after breast cancer, esophagus, stomach, and colorectal are the major cancers [1,2]. Cancer is the third most common cause of death in Iran, accounting for 14% of mortality. Overall, GI cancers account for nearly half (44.4%) of all cancer related deaths in Iran. Unfortunately, GI cancers often come to medical attention when they are at advanced stages and so limited or no effective therapies are available to treat them [3,4]. Theoretically, these cancers may be treatable in their early stage; therefore early detection is desirable.A cancer registry maintained by the International Agency for Research on Cancer (IARC) and the Institute of Public Health Research of Tehr