Spatiotemporal Mapping of Colorectal and Gastric Cancer Incidence in Hamadan Province, Western Iran (2010-2019)

Exploring the pattern of diseases in space and time enhances our understanding of truly needy areas. The present study aimed to explore spatiotemporal mapping of colorectal cancer (CRC) and gastric cancer (GC) incidence using Bayesian models and space-time scan statistics in Hamadan Province from 2010 to 2019. Study Design: An ecological time-series study.

In this study, the data on CRC and GC cases were obtained from Hamadan cancer registry. The crude standardized incidence ratio (SIR) was calculated for each county per year. Hierarchical Bayesian space-time models were fitted to estimate adjusted SIRs. Space time cluster analysis was performed using space-time scan statistic.

A total of 1864 CRC cases and 2340 GC cases were included in the analyses. The central counties, including Hamadan (smoothed SIR range: 1.24-1.28) and Tuyserkan (1.01-1.24), exhibited higher than expected number of CRC cases. Northern counties such as Razan (1.19-1.51) and Kabudarahang (1.21-1.42), along with Nahavand in the south (0.98, 1.53), also showed higher than expected number of GC cases. The most likely spatiotemporal cluster of CRC was identified in Hamadan and Tuyserkan occurring between 2015 and 2019 (relative risk [RR]=1.82, P<0.001). The most likely spatiotemporal cluster of GC was identified in Nahavand from 2010 to 2011 (RR=1.87, P<0.001).

Spatiotemporal inequality in the incidence of CRC and GC was identified in Hamadan province over the past decade. The findings may help to reduce cancer disparities and allocate effective resources in the appropriate region and time in the future.