A systematic review and meta-analysis of 696 patients concluded that KRAS status was not predictive of tumour downstaging following CRT in LARC patients (21).However we hypothesise that significant molecular heterogeneity exists within these studied tumours, and that the presence of a KRAS mutation at a level undetectable by conventional sequencing, may lead to the domination of this KRAS mutation clone when irradiated. Here, KRAS is linked to neoplasm.