Association between recurrent metastasis from stage II and III primary colorectal tumors and moderate microsatellite instability.

Colorectal cancer cells frequently have low levels of microsatellite instability (MSI-L) and elevated microsatellite alterations at selected tetranucleotide repeats (EMAST), but little is known about the clinicopathologic significance of these features. We observed that patients with stage II or III colorectal cancer with MSI-L and/or EMAST had shorter times of recurrence-free survival than patients with high levels of MSI (P = .0084) or with highly stable microsatellites P = .0415), based on Kaplan-Meier analysis. MSI-L and/or EMAST were independent predictors of recurrent distant metastasis from primary stage II or III colorectal tumors (Cox proportional hazard analysis: hazard ratio, 1.83; 95% confidence interval, 1.06-3.15; P = .0301).