‎By existing censor and skewness in survival data‎, ‎some models such as weibull are used to analyzing survival data‎.

‎In addition, parametric and semiparametric models can be obtained from baseline hazard function of Cox model to fit to survival data‎. ‎However these models are popular because of their simple usage but do not consider unknown risk factors‎, ‎that's why cannot introduce the best fit to the data necessarily‎.

‎In this paper by considering multiple random effects in Cox model‎, ‎frailty models are introduced‎. ‎Then using presented models‎, ‎esophageal cancer data in Golestan were modeled and fitted models were evaluated and compared based on generalized coefficient of determination criterion‎.