Imatinib Mesylate With or Without Bevacizumab in Treating Patients With Metastatic or Unresectable Gastrointestinal Stromal Tumor

This randomized phase III trial studies imatinib mesylate and bevacizumab to see how well they work compared to imatinib mesylate alone in treating patients with gastrointestinal stromal tumor that has spread to other parts of the body or cannot be removed by surgery. Imatinib mesylate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Monoclonal antibodies, such as bevacizumab, may interfere with the ability of tumor cells to grow and spread. It is not yet known whether imatinib mesylate and bevacizumab are more effective than imatinib mesylate alone in treating gastrointestinal stromal tumor.