The messenger RNA (mRNA) levels of the epidermal growth factor receptor (EGFR) ligands amphiregulin (AREG) and epiregulin (EREG) may be potential predictors of tumour response to cetuximab (Ctx, Erbitux, Branchburg, NJ, USA) in metastatic colorectal cancer (mCRC) patients harbouring wild-type (wt) KRAS tumours. Here, EGFR is linked to metastatic colorectal cancer.