A Comparative Study on Ecological Regression Models in Breast Cancer Risk in Iran, 2005- 2008

Breast cancer is the leading cancer among women in Iran with standardized incidence rate of 28.25. With regard to the aging and increasing cancer trends in Iranian population, the importance and geographical variations of cancer,it is necessary to identify those regions with high breast cancer incidence and get information on geographical its patterns and prominent risk factors using advanced statistical methods.
The used population in the present ecological study is all those breast cancer patients in Iran 2005-2008. We assessed the impact of cigarette, fruit and vegetable consumption, physical activity, overweight, and socioeconomic status on breast cancer using gamma-poisson, log-normal and BYM models.
Findings: Total number of registered breast cancer patients was 25152. From models used to analyze the data, unadjusted BYM had the best performance. In unadjusted models, Isfahan, Yazd, and Tehran had the highest and Sistan-and Baluchestan and Chaharmahal-and-Bakhtiyari incidence had the lowest incidence rate. After adjustment, the incidence was estimated to be the highest in Khorasan-Razavi, Khoramabad, and Hamadan and the lowest in Ardebil and Kohgiluyeh-and –Boyerahmad. Direct association between human development index (HDI) and breast cancer incidence was found to be statistically significant.
BYM model had the best fit and may cast so in future applications. Due to significant relationsip between HDI breast cancer, it is recommended to take it into account as a risk factor in future researches in this field. The incidence is generally high in central provinces.