The Panitumumab Randomized trial In combination with chemotherapy for Metastatic colorectal cancer to determine Efficacy ( PRIME ) demonstrated that panitumumab-FOLFOX4 significantly improved progression-free survival ( PFS ) versus FOLFOX4 as first-line treatment of wild-type ( WT ) KRAS metastatic colorectal cancer ( mCRC ) , the primary end point of the study .