Comparison of influential factors affecting survival of patients with colon and rectum cancer using competing risks model

Colorectal cancer is the most common cancer of digestive system and also fourth cause for death of cancer around the world. Different studies indicate that survival of patients suffering from colorectal cancer has recently developed in some areas of the world. However, it is not clear which factors involve in this improvement. This study aims at investigating some clinical and pathologic factors in prognosis of these patients with colon and rectum cancers separately. Data recorded from 1194 patients with colorectal cancer in Cancer Record Center of Research Center for Gastroenterology and Liver Disease, Shahid Beheshti University of Medical Sciences (Tehran, Iran) was used in this study. Data analysis was performed using competing risks model. Software used for data analysis was STATA, 11 version, and significance level was regarded as 0.05. Body mass index, alcohol consumption, tumor site, inflammatory bowel disease, metastasis to lymph nodes and metastasis to other organs had significant effect on death of colon cancer, while body mass index, metastasis to other organs and kind of the first treatment had significant effect (P<0.05) on rectum cancer. Median survival was 7.75±1.118 and 3.917±0.26 years for patients with colon cancer and rectum cancer respectively. Also, 1, 2, 3, 4 and 5 years of survival rates for colon cancer were 88.7%, 77.9%, 68.5%, 61.4% and 56.8%, respectively, while they were 89.1%, 74.2%, 60.7%, 47.1% and 41.9% for rectum cancer, respectively. According to the results of this study, some variables may have different impacts on colon and rectum carcinoma; therefore it is needed that the effects of the factors on different parts of the large bowel be considered separately in the future studies.