Bevacizumab in Treating Patients Who Have Undergone First-Line Therapy for Metastatic Colorectal Cancer

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 tumor cells by blocking blood flow to the tumor. It is not yet known whether giving bevacizumab as maintenance therapy is more effective than observation in treating patients with colorectal cancer.
PURPOSE: This randomized phase III trial is studying bevacizumab to see how well it works in treating patients who have undergone first-line therapy for metastatic colorectal cancer.