<qa>  What is the name of the drug used in chemotherapy?RATIONALE: Radioimmunotherapy uses radiolabeled monoclonal antibodies to locate tumor cells and deliver radioactive tumor-killing substances to them without harming normal cells. Radiation therapy uses high-energy x-rays to damage tumor cells. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining intrathecal radioimmunotherapy and radiation therapy with combination chemotherapy may kill any tumor cells remaining after surgery. 