Combination Chemotherapy and Bevacizumab With or Without Bevacizumab Maintenance Therapy in Treating Patients With Metastatic Colorectal Cancer

RATIONALE: Drugs used in chemotherapy, such as irinotecan hydrochloride, leucovorin calcium, and fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Bevacizumab may stop the growth of colorectal cancer by blocking blood flow to the tumor. It is not yet known whether giving more than one drug (combination chemotherapy) is more effective when given with or without bevacizumab in treating patients with metastatic colorectal cancer. PURPOSE: This randomized phase III trial is studying giving combination chemotherapy with or without bevacizumab to see how well it works in treating patients with metastatic colorectal cancer.