Bevacizumab and Combination Chemotherapy as First-Line Therapy in Treating Patients With Metastatic Colorectal Cancer That Cannot Be Removed by Surgery

RATIONALE: 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. Bevacizumab may also stop the growth of colorectal cancer by blocking blood flow to the tumor. Drugs used in chemotherapy, such as irinotecan, 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. Giving bevacizumab together with combination chemotherapy may kill more tumor cells. PURPOSE: This phase II trial is studying how well giving bevacizumab together with combination chemotherapy works as first-line therapy in treating patients with metastatic colorectal cancer that cannot be removed by surgery.