Spatial Clusters of Colorectal Neoplasm in the Center of Iran; a Population Based Study.

Background: Identifying the local foci and clusters of diseases can help reduce incidence and mortality by making necessary interventions. This study aimed to detect possible colorectal cancer incidence clusters using spatial analyses at point-level data at small census units in Arak, Iran, from 2009 to 2014. Methods: In this ecologic study, recorded data on colorectal cancer in Arak were collected from the Arak Cancer Registry. All records were evaluated using various methods to detect and resolve probable error events or duplicated records. Then, SaTScan software was used to explore spatial clusters. The Discrete Poisson-based Probability Model was utilized to analyze the clusters. Results: A total of 398 incident cases of colorectal cancer were identified. The mean age at diagnosis was 62.8 ± 14.6 years. Among colorectal cancer cases, 179 (45%) and 219 (55%) were females and males, respectively. Most cases were categorized with colon topography codes (n = 119, 66.5%). Three spatial clusters of colorectal cancer using individual geocodes were detected. The most high-risk cluster was located near the southern highway in Arak, a highway with transit routes for heavy and light vehicles (p=0.0004). The second significant high-risk cluster was a district located in the vast part of the center of Arak (p=0.003). The third high-risk cluster was an area in the suburb of Arak, between Farmahin-Arak Road and Northern highway (p=0.06). Conclusion: This study identified three essential clusters for the high incidence of colorectal cancer in Arak. The data would be useful for further evaluation of the environmental and lifestyle factors. Furthermore, the obtained pattern might be related to confounding impacts of environmental and lifestyle factors.