...Histologically proven diagnosis of colorectal cancer.Initially unresectable metastatic colorectal cancer not previously treated with chemotherapy for metastatic disease.At least one measurable lesion according to RECIST1.1Availability of a tissue tumour sample (primary tumour and/or metastatic sites)Previous adjuvant chemotherapy allowed only if with fluoropyrimidine monotherapy and more than 6 months elapsed between the end of adjuvant and first relapse.RAS (codons 12, 13, 59, 61, 117 and 146 of KRAS and NRAS genes) and BRAF (V600E mutation) wild type status of primary colorectal cancer or related metastasis (local or central laboratory assessment). ...