Abstract 103: Gene expression based subtypes of colorectal cancer

Colorectal cancer is a heterogeneous disease and improved molecular stratification of patients is warranted for precise treatment. Several gene expression classification systems are reported in the literature, albeit many have shown low reproducibility in external validation. A robust random forest classification system based on gene expression profiles was recently proposed, suggesting the existence of four biologically different subtypes with associations to prognosis (CMS1, CMS2, CMS3 and CMS4) (Guinney,J., et al., Nat Med, 2015). By applying the CMS classifier to high-quality gene expression profiles from a consecutive series of >400 stage I-IV primary colorectal cancers we are able to reproduce results from Guinney et al in an independent cohort. Analyses of mutational hotspots in BRAF / KRAS and the complete coding sequence of TP53 confirms enrichment of BRAF mutations in CMS1 (p