Correlations between DNA mismatch repair (MMR) and prognosis and prediction of treatment efficacy in stage II/II colon cancer

Abstract

To investigate the role of DNA mismatch repair (MMR) as a prognostic indicator of radical resection and a predictor of fluorouracil-based adjuvant therapy benefit in patients with stage II/III colon cancer. The clinicopathological characteristics of 172 patients with stage II/III colon cancer who underwent radical resection were retrospectively analyzed. Immunohistochemical staining was used to detect the expression of DNA mismatch repair (MLH1/MSH2/MSH6/PMS2) in the tumor tissues. Among a total of 172 patients, there were 38 (22.1%) cases with defective DNA mismatch repair (dMMR) and 134 (77.9%) cases with proficient DNA mismatch repair (pMMR). Among the 115 patients who did not receive adjuvant chemotherapy, those with tumor displaying dMMR had a better 5-year overall survival (OS) rate and disease-free survival (DFS) rate than the patients with proficient DNA mismatch repair (pMMR) (88.0% vs. 66.7%, P = 0.040; 84.0% vs. 60.0%, P = 0.034). The benefit of adjuvant chemotherapy differed significantly according to the MMR status. Adjuvant 5-Fu chemotherapy improved the 5-year overall survival rate among 134 patients with pMMR (86.4%) than that in patients treated by surgery alone (66.7%, P = 0.012). By contrast, there was no benefit of adjuvant 5-Fu chemotherapy in the patients with dMMR (61.5% vs. 86.4%, P = 0.062), which was even more clear the 5-year disease-free survival rate (53.8% vs. 84.0%, P = 0.038). MMR status is a predictor of the benefit of adjuvant chemotherapy with fluorouracil in stage II/III colon cancer. Patients with stage II/III colon cancer displaying dMMR have a better prognosis than those with pMMR.