Radiation Therapy or Combination Chemotherapy in Treating Patients With Clinically or Radiologically Progressive Low-Grade Gliomas

primary central nervous system neoplasms, recurrent childhood brain stem glioma, untreated childhood brain stem glioma, recurrent childhood cerebellar astrocytoma, untreated childhood cerebellar astrocytoma, childhood low-grade cerebral astrocytoma, recurrent childhood cerebral astrocytoma, childhood oligodendroglioma, recurrent childhood visual pathway and hypothalamic glioma, untreated childhood visual pathway and hypothalamic glioma, childhood spinal cord neoplasm, interventional