RATIONALE: Drugs used in chemotherapy, such as oxaliplatin, irinotecan, fluorouracil and leucovorin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Monoclonal antibodies, such as bevacizumab and cetuximab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. Giving combination chemotherapy together with monoclonal antibody therapy may kill more tumor cells.