Study to Evaluate the Effects of Panitumumab if Combined With Chemotherapy for 2nd Treatment of Colorectal Cancer

Subjects with metastatic colorectal cancer with KRAS-wildtype will be randomized in a 1:1 ratio to receive a 2nd line treatment regimen of panitumumab plus oxaliplatin and capecitabine (XELOX) or XELOX alone. Before randomization tumour of all subjects will be analyzed to detect the KRAS mutational status. Subjects will only be randomized into these two arms if the tumour shows KRAS wild-type. Subjects with KRAS mutant colorectal tumours will receive XELOX alone. Subjects will receive treatment cycles every three weeks. Treatment will continue until subjects are diagnosed with disease progression or intolerable toxicity, at which time the subjects will be withdrawn from the treatment phase. If a subject withdraws from chemotherapy due to toxicity the subjects will be allowed to continue with panitumumab monotherapy with or without one of the chemotherapy components until disease progression. After withdrawing panitumumab and XELOX treatment, all subjects will end the treatment phase and will enter a follow-up phase until 6 months after the last patient stopped treatment (with a safety follow-up visit after 56 days ± 3 days and long term follow-up visits every 12 weeks). During the treatment phase subjects will be evaluated for tumour response every 9 weeks (± one week) through to week 45, and every 12 weeks (± two weeks) thereafter, until disease progression. Subjects with symptoms suggestive of disease progression should be evaluated for tumour response at the time symptoms occur.