Microsatellite instability in sporadic colorectal cancer is not an independent prognostic factor

Hereditary non-polyposis colorectal cancer (HNPCC) is linked to an inherite d defect in the DNA mismatch repair system. DNA from HNPCC tumours shows mi crosatellite instability (MSI). It has been reported that HNPCC patients ha ve a better prognosis than patients with sporadic colorectal cancer. We exa mined whether the presence of MSI in a series of unselected colorectal tumo urs carries prognostic information. In a series of 181 unselected colorecta l tumours, 22 tumours (12%) showed MSI. Survival analysis at 5-10 years fol low-up showed no statistically significant difference in prognosis between MSI-positive and -negative tumours. Our results suggest that the MSI phenot ype as such is not an independent prognostic factor. (C) 1999 Cancer Resear ch Campaign.