 - Group A 50 Patients: mFOLFOX6 panitumumab combination therapy, once every two weeks oxaliplatin OXA: 85 mgm2day 1; levofolinate calcium l-LV: 200 mgm2day 1; bolus 5-FU: 400 mgm2day 1; infusional 5-FU: 2400 mgm2day 1-3; panitumumab: 6 mgkg 