Radiation Therapy Followed By Combination Chemotherapy in Treating Young Patients With Supratentorial Primitive Neuroectodermal Tumors

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. Drugs used in chemotherapy, such as lomustine, cisplatin, 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 radiation therapy followed by combination chemotherapy after surgery may kill any remaining tumor cells. PURPOSE: This phase II trial is studying how well giving radiation therapy followed by combination chemotherapy works in treating young patients with supratentorial primitive neuroectodermal tumors.