Abstract A87: Correlation between microsatellite instability and clinical characteristics and outcome of colorectal cancer in an Iranian population

Abstract Widespread microsatellite instability (MSI) occurs in nearly 15% of sporadic colorectal cancers. Large bowel carcinomas with high-frequency MSI (MSI-H) (instability at > or = 30% of microsatellite loci) are believed to display distinctive pathologic features and to behave less aggressively than microsatellite-stable (MSS) tumors and carcinomas with low-frequency MSI (MSI-L) (instability at < 30% of microsatellite loci). In this study we would like to show the impression of MSI on clinical condition and outcome of patients with colorectal adenocarcinoma. Methods: MSI status was evaluated in 600 large bowel adenocarcinomas using polymerase chain reaction (PCR) and sequencing. Tumors that showed instability with at least two microsatellite markers were classified as MSI-H, whereas the other tumors were classified as MSI-L (instability at one locus) or MSS (no instability). Results: MSI-H was detected in 51.6% of CRC patients. The prevalence of proximal lesions in the MSI-H group (38.7%) was higher than in the MSS group (27.4%). The percentage of moderately differentiated tumors was slightly lower in the MSI-H group (16.3%) when compared to the MSS group. Eight mutations were detected in five patients with 32 MSI-H. Conclusion: Assessment of MSI status is an essential step in discovering genetic characterizations of large bowel carcinomas and identifies a subset of tumors with distinct clinical, pathologic, and biologic features. Citation Information: Cancer Prev Res 2010;3(1 Suppl):A87.