Elevated Microsatellite Alterations at Selected Tetranucleotides (EMAST) in Colorectal Cancer is Associated with an Elderly, Frail Phenotype and Improved Recurrence-Free Survival

Elevated microsatellite alterations at selected tetranucleotides (EMAST) is a poorly investigated form of microsatellite instability (MSI) in colorectal cancer (CRC). The aim of this study was to investigate the clinicopathological features of EMAST in CRC and its relation to outcome. A population-based, consecutive cohort of surgically treated stage I–III CRC patients investigated for high-frequency MSI (MSI-H) and EMAST. Clinicopathological differences were reported as odds ratios (OR) and survival was presented as hazard ratios (HR) with 95% confidence intervals (CIs). Of 161 patients included, 25% were aged > 79 years. There was a large overlap in the prevalence of EMAST (31.7%) and MSI-H (27.3%) [82.4% of EMAST were also MSI-H]. EMAST had the highest prevalence in the proximal colon (OR 15.9, 95% CI 5.6–45.1; p