Document Type: Research Articles
Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
Department of Health and Community Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Department of Radiotherapy, Shahid Baheshti University of Medical Sciences, Tehran Iran.
Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
Digestive Disease Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Objectives: Colorectal cancer (CRC) may now be the second most common cancer in the world. The aim of this
study was to determine whether clusters of high and low risk of CRC might exist at the neighborhood level in Tehran
city. Methods: In this study, new cases of CRC provided from Cancer Registry Data of the Management Center of
Ministry of Health and Medical Education of Iran in the period from March 2008 to March 2011 were analyzed. Raw
standardized incidence rates (SIRs) were calculated for CRC in each neighborhood, along with ratios of observed to
expected cases. The York and Mollie (BYM) spatial model was used for smoothing of the estimated raw SIRs. To
discover clusters of high and low CRC incidence a purely spatial scan statistic was applied. Results: A total of 2,815
new cases of CRC were identified and after removal of duplicate cases, 2,491 were geocoded to neighborhoods. The
locations with higher than expected incidence of CRC were northern and central districts of Tehran city. An observed
to expected ratio of 2.57 (p<0.001) was found for districts of 2, 6 and 11, whereas, the lowest ratio of 0.23 (p<0.001)
was apparent for northeast and south areas of the city, including district 4. Conclusions: This study showed that there
is a significant spatial variation in patterns of incidence of CRC at the neighborhood level in Tehran city. Identification
of such spatial patterns and assessment of underlying risk factors can provide valuable information for policymakers
responsible for equitable distribution of healthcare resources.