A Comparison between Accelerated Failure-time and Cox Proportional Hazard Models in Analyzing the Survival of Gastric Cancer Patients

Abstract

Background: Gastric cancer is the one of the most prevalent reason of cancer-related death in the world. Survival of patients after surgery involves identifying risk factors. There are various models to detect the effect of risk factors on patients’ survival. The present study aims at evaluating these models.

Methods: Data from 330 gastric cancer patients diagnosed at the Iran cancer institute during 1995-99 and followed up the end of 2011 were analyzed. The survival status of these patients in 2011 was determined by reopening the files as well as phone calls and the effect of various factors such as demographic, clinical, treatment, and post-surgical on pa-tients’ survival was studied. To compare various models of survival, Akaike Information Criterion and Cox-Snell Re-siduals were used. STATA 11 was used for data analyses.

Results: Based on Cox-Snell Residuals and Akaike Information Criterion, the exponential (AIC=969.14) and Gom-pertz (AIC=970.70) models were more efficient than other accelerated failure-time models. Results of Cox propor-tional hazard model as well as the analysis of accelerated failure-time models showed that variables such as age (at di-agnosis), marital status, relapse, number of supplementary treatments, disease stage, and type of surgery were among factors affecting survival (P<0.05).

Conclusion: Although most cancer researchers tend to use proportional hazard model, accelerated failure-time mod-els in analogous conditions — as they do not require proportional hazards assumption and consider a parametric sta-tistical distribution for survival time— will be credible alternatives to proportional hazard model.