 This open label study will exploratorily examine efficacy and safety of 5-FULV panitumumab combination therapy or mFOLFOX6 panitumumab combination therapy in the patients with chemotherapy-naïve unresectable, advancedrecurrent colorectal carcinoma of KRAS wild-type who have been treated with 6 cycles 2 weekscycle site visit of first-line mFOLFOX6 panitumumab combination therapy The study will enroll approximately 100 patients. All patients will receive 6 cycles of Protocol Treatment 1: mFOLFOX6 panitumumab combination therapy 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 once every two weeks. Then they will be randomly assigned by chance, like flipping a coin to one of the treatment groups. 