Site-Specific Evaluation of Prognostic Factors on Survival in Iranian Colorectal Cancer Patients: A Competing Risks Survival Analysis

Background: Colorectal cancer (CRC) is one of the most malignant cancers, but prognosis varies in differentparts of the world. Knowing the prognostic factors of the cancer is clinically important for prognosis and treatmentapplication objectives. However, evaluation of these factors overall does not provide thorough understanding ofthe cancer. Therefore, this study aimed to evaluate prognostic factors of colon and rectal cancers site-specifically,via a competing risks survival analysis with colon and rectum as competing causes of death.
Methods: A total of1,219 patients with CRC diagnosis according to the pathology reports of our cancer registry, from 1 January2002 to 1 October 2007, were entered into the study. Demographic and clinicopathological factors with regard tosurvival of patients were analyzed using univariate and multivariate competing risks survival analysis, utilizingSTATA statistical software.
Results: The results of univariate analysis showed that gender, body mass index(BMI), alcohol history, inflammatory bowel disease (IBD), tumor size, tumor grade and pathologic stage weresignificantly associated with colon cancer and BMI, personal history of cancer, pathologic stage and the kind offirst treatment used were significantly related to rectal cancer. In the multivariate analysis, BMI, IBD, tumorgrade and pathologic stage of the cancer were significant prognostic factors for colon cancer and BMI and thekind of first treatment used were significant prognostic factors of rectal cancer. Also 1, 2, 3, 4 and 5 year andoverall adjusted survival of patients with rectal cancer was better than those of colon cancer.
Conclusion: Basedon our findings, CRC is not a single entity and its sub-sites should be evaluated separately to reveal hiddenassociations which may not be revealed under general modeling.