Overall, for colorectal cancers treated with curative intent (generally stage II or III), data support an association between MSI and good prognosis, and weaker evidence suggests that KRAS and BRAF mutations, which are mutually exclusive, indicate poor prognosis in MSI-negative tumours.6, 7, 8, 9, 10, 11 However, MSI-positive colorectal cancers tend to be BRAF-mutant and KRAS-wild-type, so statistical interactions could exist between these prognostic biomarkers. Here, KRAS is linked to colorectal cancer.