Demographic and Pathological Predictors of Colorectal Cancer Survival in Competing Risk Model, Using Generalized Weibull Distribution

Objectives: To investigate the prognosis factors of survival in patients with colorectal cancer in presence of competing risks, using generalized Weibull distribution, and to compare the results of Weibull model as well as semi parametric models. Methods: A total of 1462 patients with colorectal cancer, registered in cancer registry center of research institute of gastroenterology and liver disease (from 2004 to 2015), Taleghani hospital, Tehran, Iran entered this study. Death and the causes of death were confirmed via telephone contact to patients’ families. The demographic and clinical features included age at diagnosis, sex, family history of CRC, body mass index (BMI), tumor size and tumor site extracted from hospital documents. Generalized Weibull distribution, Cox regression analysis and Fine-Gary model were used to assess the prognosis of CRC survival. The analysis was carried out using R software version 3.0.2. P value less than 0.05 were considered significant. Results: Overall, 1060 CRC patients with completed data were included in the analysis. 58% were men and the mean ± SD of age at diagnosis was 53.67 ± 0.46 years. The mean ± SD of survival time was 56.96 ± 1.46 with median = 45.5 months. 380 patients (35.5%) died from CRC and 49 patients (4.6%) died from other causes of death, such as myocardial infarction, stomach cancer, liver cancer etc. Generalized Weibull model with competing risk analysis and other models indicated age and BMI as the prognosis. Conclusions: This study indicated age and BMI as the prognosis, using a generalized Weibull model with competing risk analysis. Also according to the survival curve estimation, generalized Weibull model with competing risk has a better fit to the data, compared to Weibull model.