Chemotherapy Followed by Bone Marrow or Peripheral Stem Cell Transplantation in Treating Patients With Glioblastoma Multiforme or Brain Stem Tumors

DISEASE CHARACTERISTICS: Glioblastoma multiforme (GBM) or brain stem tumor following surgery (if feasible) and local radiotherapy, as follows: Pathologically confirmed primary GBM Gliosarcomas and multifocal GBM eligible Unbiopsied diffuse intrinsic pontine tumors Nonenhancing with gadolinium on MRI T1 hypodense and T2 hyperdense No recurrent or progressing disease following radiotherapy No leptomeningeal dissemination by radiographic evaluation including head MRI and either whole-spine MRI with gadolinium or myelogram Positive CSF cytology alone allowed No extraneural metastases PATIENT CHARACTERISTICS: Age: 6 to under 60 Performance status: Karnofsky 70%-100% (over age 16) Lansky 70%-100% (ages 6-16) Hematopoietic: Not specified Hepatic: Bilirubin less than 2.0 mg/dL AST or ALT less than 5 times normal PT and aPTT normal (consult with principal investigator if abnormal) Renal: Creatinine clearance at least 50 mL/min/1.73 sqm Cardiovascular: No evidence of myocardial infarction or ischemia on EKG Other: No active infection at time of leukapheresis Able to tolerate anticoagulation PRIOR CONCURRENT THERAPY: Radical surgery and involved-field radiotherapy (at least 4,500 cGy) completed within 6 weeks prior to entry Second surgical debulking following radiotherapy strongly encouraged for patients with residual tumor mass or suspected radionecrosis Requirement for surgery waived for unresectable brainstem tumors No prior chemotherapy except corticosteroids