While in the advanced setting right colon cancer is associated with a worse outcome, this negative prognostic effect has been not definitively demonstrated in the adjuvant setting. We have analyzed the outcome data from 3 large randomized trials (SITAC-1; SMAC and TOSCA) assessing adjuvant therapy in colon cancer patients with stage II and III. Furthermore, since previous trials were not powered to assess the prognostic role of transversum colon cancer, we analyzed this site independently.
In order to define the prognostic effect of sidedness we assessed three randomized trials of adjuvant therapy (SITAC, 5FU/FA vs control, 821 patients; SMAC, intraportal 5FU vs 5FU/FA, 990 patients; TOSCA, FOLFOX or XELOX three vs six months 3513 patients) carried out in Italy from 1987 to 2013 and including 5324 patients. Survival and disease-free survival, overall and in each trial, were analyzed according to right, transversum and left colon location. Right-sided was considered caecum to hepatic flexure, left-sided splenic flexure to rectum and trasversum hepatic to splenic flexure. Statistical analysis considered all randomized patients according to allocation arm, with available data on putative prognostic factors. Analysis was planned in order to provide overall and by stage results.
5324 patients were included in this analysis; 2490 patients were males and 2834 females. Median age was 64 years. 2240 patients had a stage II colon cancer and 3084 a stage III. Right tumors were 1573 (30%), trasversum 822 (15%) and left 2929 (55%). Patients characteristics were well balanced among the three trials. In all the 5234 patients DFS was not affected by tumor location (right colon versus left, HR = 1.01; 95% CI = 0.89-1.15) while right tumor was associated to a worse OS compared to left tumor (HR = 1.21; 95% CI = 1.05-1.40) In stage II patients there was no difference in terms of DFS and OS among the three different tumor location while in stage III patients, right colon cancer had a worse outcome both in DFS and OS than left tumor (HR: 1.37 95% CI = 1.16-1.64, p
This is the largest analysis demonstrating the prognostic effect of tumor location in colon cancer patients receiving adjuvant chemotherapy. The effect however is present only in stage III but not in stage II colon cancer.
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All authors have declared no conflicts of interest.