Original researchPrognostic impact of tumor location in stage IV colon cancer: A propensity score analysis in a multicenter study

- Prognostic significance of tumor location in colon cancer is controversial.
- Propensity score analysis was performed in stage IV colon cancer.
- Stage IV right-sided colon cancer was diagnosed in a more advanced state.
- Stage IV right-sided colon cancer showed a significantly worse prognosis.
- Stage IV right-sided colon cancer was suggested to be oncologically more aggressive.

Background: Right-sided colon cancer is considered to be biologically different from left-sided colon cancer; however, conflicting results have been reported regarding differences in prognosis. We aimed to clarify the prognostic impact of tumor location in stage IV colon cancer. Methods: Stage IV colon cancer treated from January 1997 to December 2007 (n = 2208) were retrospectively studied. Clinical and pathological features were compared between right-sided colon cancer (cecum, ascending, and transverse colon) and left-sided colon cancer (descending, sigmoid, and rectosigmoid colon). The impact of tumor location on cancer-specific survival (CSS) was analyzed in a multivariate analysis and propensity score analysis to mitigate the differences in background features. Results: Right-sided colon cancer was associated with older age, female sex, larger tumor size, poorly differentiated adenocarcinoma, mucinous adenocarcinoma, and signet-ring cell carcinoma, a more advanced state within stage IV disease, and a worse CSS. In the cohort matched by propensity scores for background clinicopathological features, tumor location in the right-sided colon was associated with a significantly worse CSS (hazard ratio 1.2, 95% confidence interval 1.1-1.4, p = 0.008) in patients treated with palliative primary tumor resection, but not in those treated with R0 resection or no resection. Conclusion: Right-sided colon cancer were diagnosed at a more advanced state within stage IV disease and showed a significantly worse prognosis than left-sided colon cancer, suggesting that stage IV right-sided colon cancer is oncologically more aggressive than left-sided colon cancer.