Is there a difference in survival between right- versus left-sided colon cancers?

Background: The incidence of right-sided colon cancers has been increasing in recent years. It is unclear whether patient prognosis varies by tumor location. In this study, we have compared the survival of right-and left-sided colon cancers in a longitudinal population-based database. Methods: A retrospective survival analysis was performed using the Surveillance, Epidemiology, and End Results Program (SEER) database between 1988 and 2003 on subjects who underwent surgical resection for the a primary diagnosis of pathologically confirmed invasive colon adenocarcinoma. Cox proportional hazard regression analysis was used to assess long-term survival outcomes comparing right-sided (cecum to transverse colon, excluding appendix) versus left-sided (splenic flexure to sigmoid, excluding rectum) colon cancers. Results: A total of 77,978 subjects were identified with adenocarcinoma of the colon. Overall median survival was 83 months. Median survival for right-sided cancers was 78 vs. 89 months for left-sided cancers (P < .001). By Cox proportional hazard regression analysis, controlling for statistically significant confounders, including age, sex, race, marital status, tumor stage, tumor size, histologic grade, number of lymph nodes examined, and year of diagnosis, right-sided colon cancers were associated with a 5% increased mortality risk compared with left-sided colon cancers (hazard ratio, 1.04; 95% confidence interval, 1.02-1.07). These findings were consistent across subsets of subjects. Conclusion: On the basis of analysis of information from the SEER database, we found that right-sided colon cancers have a worse prognosis than left-sided colon cancers. The reason for this remains unclear but may be due to biological and/or environmental factors and may have particular bearing, given the rising incidence of right-sided colon cancers.