RATIONALE: Radiolabeled monoclonal antibodies can find tumor cells and either kill them or carry tumor-killing substances to them without harming normal cells. Giving radioactive substances together with antibodies may be effective treatment for some advanced cancers. Drugs used in chemotherapy, such as irinotecan hydrochloride, fluorouracil, and leucovorin calcium (FOLFIRI), work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. 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. Giving radiolabeled monoclonal antibodies together with combination chemotherapy and bevacizumab may be an effective treatment for colorectal cancer.