Second-Line Combination Chemotherapy With or Without Bevacizumab in Treating Patients With Metastatic Colorectal Cancer Who Have Received First-Line Chemotherapy and Bevacizumab

RATIONALE: Drugs used in chemotherapy, such as irinotecan, oxaliplatin, leucovorin, and fluorouracil, 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, 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. It is not yet known whether combination chemotherapy is more effective with or without bevacizumab in treating metastatic colorectal cancer. PURPOSE: This randomized phase III trial is studying second-line combination chemotherapy to see how well it works compared with or without bevacizumab in treating patients with metastatic colorectal cancer who have received first-line chemotherapy and bevacizumab.