Data from oxaliplatin and cetuximab in first-line treatment of metastatic colorectal cancer and cetuximab combined with irinotecan in first-line therapy for metastatic colorectal cancer trials have indicated that the addition of cetuximab during first-line treatment with infusional fluorouracil, leucovolin and oxaliplatin or fluorouracil, leucovolin and irinotecan was not beneficial in KRAS-mutated tumours, although these patients benefited from chemotherapy alone (4,5). This evidence concerns the gene KRAS and metastatic colorectal cancer.