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

Abstract

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.

FIG. 1

Kaplan–Meier survival estimates for overall unadjusted survival of left-versus right-sided adenocarcinoma of the colon.

FIG. 2

Adjusted Kaplan–Meier survival estimates for overall survival of left-versus right-sided adenocarcinoma of the colon. Note magnified y-axis range. Multivariate Cox proportional hazard regression model includes the following variables: subject age, sex, race, marital status, tumor side, American Joint Committee on Cancer stage, tumor size, histologic grade, number of lymph nodes examined, and year of diagnosis.

FIG. 3

Adjusted Kaplan–Meier survival estimates for overall survival of adenocarcinoma of the colon stratified by tumor stage for left- and right-sided tumors. Multivariate Cox proportional hazard regression model includes the following variables: subject age, sex, race, marital status, tumor side, American Joint Committee on Cancer stage, tumor size, histologic grade, number of lymph nodes examined, and year of diagnosis.

FIG. 4

Adjusted hazard ratio with 95% confidence intervals for mortality comparing right-sided colon cancers relative to left-sided colon cancers in the following cohorts: female subjects, male subjects, subjects of white race, subjects of black race, American Joint Committee on Cancer stage I, II, III and IV, and histology grades I, II, and III/IV. UB, upper bound; LB, lower bound.