EGFR and metastatic colorectal cancer: KRAS exon 2 mutations were the first validated predictive biomarker for primary resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab and panitumumab) in patients with metastatic colorectal cancer (mCRC) (Amado et al, 2008; Van Cutsem et al, 2009).