Panitumumab in Cetuximab Refractory KRAS Wild-Type Colorectal Cancer

* Panitumumab will be given to the participants through a central line. A central line is a long, thin tube (catheter) that is inserted through the skin into a large vein in the chest. This is placed by a radiologist or surgeon. * Panitumumab will be given in 4-week cycles. Panitumumab infusions will be given on days 1 and 15 of each cycle (every 2 weeks). * The following procedures will be performed on days 1 and 15 of each cycle, before each infusion: physical exam; questions about any symptoms or side effects; performance status; routine blood tests and CT or MRI (every 2 cycles). * Participants can continue to receive panitumumab until their disease gets worse or they experience unacceptable side effects.