Prediction of Colorectal Cancer Incidence Rate in the Counties of Fars Province, Iran: An Application of Small Area Estimation

Colorectal cancer (CRC) is one of the main causes of mortality and morbidity worldwide. Socio-economic status is one of the most important related factors with CRC.

In this study, we used the human development index (HDI) as one of the common measures of socio-economic status to predict the incidence rate of CRC in the counties of Fars Province in Iran.

In this ecological study, we used the medical records of 108 patients with CRC from Fars province, who referred to Shahid Faghihi Hospital in Shiraz from January 2011 to March 2013. Since sample sizes were not efficient in all the counties, we used the log-normal model within small area estimation framework to have a reliable prediction for the incidence rate in each county. As using related auxiliary variables is necessary in small area models, we considered the HDI of counties as an auxiliary variable.

The findings showed that there was a significant direct relationship between HDI and CRC incidence rate. Furthermore, the highest predicted rates were observed in the northern and eastern parts of the province.

In order to compensate the deficiency of sample size in some of the counties, we used a small area model to predict the CRC incidence rate. The highest incidence rates mostly occurred in the counties with the highest HDI. It is observed that the counties with higher incidence rates are closer to more industrial provinces and the counties with lower incidence rates are closer to less industrial provinces. So, it seems that development disparities strongly affected the incidence rates.