For this randomised , open-label , phase 3 head-to-head study , we enrolled patients ( from centres in North America , South America , Europe , Asia , Africa , and Australia ) aged 18 years or older with chemotherapy-refractory metastatic colorectal cancer , an Eastern Cooperative Oncology Group ( ECOG ) performance status of 2 or less , and wild-type KRAS exon 2 status .