The present study aimed to investigate the expression level of DNA mismatch repair gene (MMR) in in sporadic colorectal cancer (SCRC) in eastern China, and to investigate the association between MMR status and prognosis of patients with SCRC. Patient archives from the Department of Gastrointestinal Surgery of Weihai Municipal Hospital (Weihai, China) were retrospectively collected between January 2011 and January 2012. Of the 221 consecutive patients identified, 192 patients who met the criterion were deemed eligible for inclusion. Immunohistochemistry (IHC) was conducted to detect the expression of MMR proteins MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MSH6 and PMS1 homolog 2, mismatch repair system component (PMS2) expression and mutation in sporadic colorectal cancer (SCRC). Kaplan-Meier plots and log-rank tests were performed to conduct survival analysis and Cox proportional hazard regression models were conducted to determine independent prognostic factors. The total rate of deficient MMR (dMMR) was 14.58% (28/192): MSH6, 0.52% (1/192); PMS2, 4.17% (8/192); MSH2/MSH6, 3.65% (7/192); and MLH1/PMS2, 6.25% (12/192). The dMMR group had a significantly longer overall survival time compared with proficient MMR (pMMR) group (P=0.017). Disease-free survival time of dMMR group was also longer than pMMR group (P=0.027). Multivariate analysis using the Cox regression model confirmed that MMR status was an independent prognostic factor for SCRC. Loss of MMR expression was indicative of a favorable outcome for patients with SCRC, and MMR status could be viewed as an independent prognostic factor.
Keywords: immunohistochemistry; microsatellite instability; mismatch repair; prognosis; sporadic colorectal cancer.