Mapping of Stomach, Colorectal, and Bladder Cancers in Iran, 2004–2009: Applying Bayesian Polytomous Log

Marzieh Nasrazadani, Mohammad Reza Maracy, Emanuela Dreassi, Behzad Mahaki

Abstract


Background: According to the last report of Iran cancer registry, stomach, colorectal, and bladder cancers are the most prevalent cancers. The present study focused on separating the latent risk surface into shared and disease‑specifc components.

Methods: In this study, data consisting of stomach, colorectal, and bladder cancers in 30 provinces of Iran during 2004–2009 are considered. These data are analyzed by polytomous logit model. The incidence of stomach cancer acts as the reference category (the surrogate for smoking). Then, the log odds are decomposed into shared and specifc structured spatial and unstructured spatial components. These latent components help to
detect spatial patterns of shared and disease‑specifc risk factors.

Results: Central, Southern, Eastern, and Southwestern provinces are supposed as high‑risk regions for shared risk factor for colorectal and bladder cancers. This shared risk factor is slightly associated more with bladder than with
colorectal cancer. Northern, northwestern, and central regions and also three borderline provinces in southwestern are high‑risk regions for colorectal cancer. Central, eastern, southern, and western strip
of the country except Ilam are found as the high‑risk regions of bladder cancer.

Conclusions: After considering known shared risk factor of the three cancers, it turns out that colorectal and bladder cancers have unknown shared risk factor. The signifcant difference in their lifestyle and eating
habits could be an assumption of the risk factor.

Keywords: Colorectal neoplasms, disease mapping, polytomous logit model, shared component model, stomach neoplasms, urinary bladder neoplasms


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