For patients with unresectable RAS wild-type (WT) recurrent or metastatic colorectal cancer (mCRC), standard first-line treatment includes chemotherapy combined with either an anti-epidermal growth factor receptor (EGFR) monoclonal antibody (for example, panitumumab or cetuximab) or an antivascular endothelial growth factor (VEGF) antibody (bevacizumab)1–3. This evidence concerns the gene EGFR and metastatic colorectal cancer.