Use of BRAF and KRAS Somatic Mutation as a Molecular Marker of Serrated Polyposis in Patients Not Fulfilling Who Criteria

determined mutation positive when a PCR product generated from a tumor tissue exhibited at least one new peak compared to the product from the matching normal tissue.Statistical Analysis: The Kaplan-Meier method was used for estimating recurrence-free survival.Cox proportional hazard analysis was used to evaluate the association between MSI status and other clinicopathological factors for predicting recurrent distant metastasis.The P value less than 0.05 was considered to be statistically significant.Results: Stage II and III patients with MSI-L and/or EMAST had a shorter recurrence-free survival than patients with high levels of MSI (MSI-H) (P=0.0084) or with highly stable microsatellites (H-MSS) (P=0.0415) by Kaplan-Meier analysis.MSI-L and/or EMAST are independent predictors of recurrent distant metastasis in primary stage II and III CRCs by Cox proportional hazard analysis (Hazard Ratio: 1.83, P=0.0301).Compatible with other studies, the present study also showed that MSI-H is associated with proximal location and exhibited lowest risk for recurrent distant metastasis.Conclusions: Our results showed that MSI-L/EMAST is a predictive factor of stage II/III primary CRC for recurrent distant metastasis.Because MSI-L/EMAST CRC is different from MSI-H and H-MSS CRC, we proposed to define MSI-L/EMAST as one group and named this group of CRC moderate MSI (MSI-M).