Radiation Therapy and Combination Chemotherapy in Treating Young Patients With Metastatic Medulloblastoma Who Have Undergone Surgery

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Drugs used in chemotherapy, such as lomustine, vincristine, and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving radiation therapy together with combination chemotherapy after surgery may kill any tumor cells that remain. PURPOSE: This phase II trial is studying giving radiation therapy together with combination chemotherapy to see how well it works in treating young patients with metastatic medulloblastoma who have undergone surgery.