OBJECTIVES Colorectal cancer is the third most common cancer in Scotland, with nearly 4,000 cases reported in 2011 and 5.2% increase in incidence in the previous 10 years. Recent studies have shown that a subgroup of metastatic colorectal cancer (mCRC) patients with wild-type (wt) RAS (KRAS and NRAS exons 2, 3, 4) expressing tumours are likely to have enhanced response to anti-EGFR treatment compared to patients with mutant RAS exons^(2,3,4)