Cetuximab is an immunoglobulin G1 monoclonal antibody that binds to the extracellular domain of the epidermal growth factor receptor (EGFR) blocking ligand-induced auto-phosphorylation and subsequent receptor mediated signalling.1,2 Cetuximab in combination with chemotherapy is effective in the treatment of EGFR-expressing tumors including metastatic colorectal cancer (mCRC).2,3. This evidence concerns the gene EGFR and metastatic colorectal cancer.