Prognostic factors of colorectal cancer based on weibull distribution with nonconstant shape

The commonest malignant cancer in the lower gastrointestinal tract is colorectal cancer which is the third cause of death due to cancer in the world. The incidence of this type of cancer in Iran has increased during last recent years. The prsent study aimed to detemine prognostic factors of colorectal cancer based on weibull distribution with nonconstant shape.

In this article we analyzed survival of 1060 patients with colorectal cancer who registered in Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences (Tehran, Iran) from 2004 to 2015. Weilbull parametric model with non-constant shape parameter were used for determination of prognostic factors. The results were compared to regular Weibull distribution and the best method were choosed based on AIC criteria.

On constant shape parameter, age at diagnosis, tumor size and the tumor site had effect on survival time with AIC of 20037. On non-constant shape parameter, sex, age at diagnosis, tumor size, the tumor site and the body mass index were significant on survival of these patients with AIC of 19994.

Remarkably, based on these data and AIC criteria, the Weibull with non-constant shape parameter chose so that sex, age at diagnosis, tumor size, the tumor site and the body mass index of these patients were recognized as prognostic factors in their survival