Prognostic Impact of Deficient Mismatch Repair in CRC
Mismatch repair (MMR) status is an important prognostic factor in patients with colorectal cancer. A meta-analysis of 14 studies involving microsatellite instability and one study of immunohistochemical analysis for MLH1/MSH2/MLH6 proteins involving 7803 patients with stage II/III mCRC was performed using the ACCENT database (Sargent DJ, et al. ASCO 2014. Abstract 3507). In this analysis, 23.1% of stage II and 14.9% of stage III patients exhibited deficient MMR (dMMR). dMMR status was more associated with female sex, higher T stage, and right-sided tumor location. Compared with proficient MMR, dMMR was strongly associated with improved overall survival and time to recurrence in stage II patients treated with surgery alone (both, P = .01). While this study confirms the prognostic utility of MMR status in stage II mCRC and treatment outcome in stage III patients, it does not currently have predictive value to impact patient management.