RATIONALE: Radioactive drugs, such as iodine I 131 metaiodobenzylguanidine (MIGB), may carry radiation directly to tumor cells and not harm normal cells. Drugs used in chemotherapy, such as irinotecan and vincristine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving iodine I 131 MIGB together with irinotecan and vincristine may kill more tumor cells.