RATIONALE: Imatinib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. 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. Drugs used in chemotherapy, such as cyclophosphamide, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Bevacizumab and cyclophosphamide may also stop the growth of tumor cells by blocking blood flow to the tumor. Imatinib and bevacizumab may help cyclophosphamide work better by making tumor cells more sensitive to the drug. Giving cyclophosphamide once a day together with imatinib and bevacizumab may kill more tumor cells.