Phase II Randomized Study of First-Line Therapy Comprising Bevacizumab and Irinotecan Hydrochloride, Leucovorin Calcium, and Fluorouracil (FOLFIRI) Versus Bevacizumab and Irinotecan Hydrochloride and Capecitabine (XELIRI) in Patients With Unresectable Metastatic Colorectal Cancer [ACCORD]

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 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. It is not yet known which combination chemotherapy regimen is more effective when given together with bevacizumab in treating patients with colorectal cancer.

PURPOSE: This randomized phase II trial is studying bevacizumab to compare how well it works when given together with two different combination chemotherapy regimens as first-line therapy in treating patients with metastatic colorectal cancer that cannot be removed by surgery.