Chemotherapy and Stem Cell Transplantation in Treating Children With Central Nervous System Cancer

DISEASE CHARACTERISTICS: Histologically confirmed primary central nervous system malignancy Recurrent, persistent, or progressive disease after at least 1 prior first-line treatment regimen PATIENT CHARACTERISTICS: Age 18 and under at initial diagnosis Performance status ECOG 0-2 Life expectancy At least 8 weeks Hematopoietic Absolute neutrophil count greater than 750/mm^3 WBC greater than 2,500/mm^3 Platelet count greater than 100,000/mm^3 No underlying myelodysplasia, stem cell disorder, or other inherent hematologic synthetic defect Hepatic Liver function tests less than 2 times normal OR Absence of active hepatitis by liver biopsy Bilirubin less than 1.5 mg/dL Renal Glomerular filtration rate greater than 60 mL/min by radionucleotide assay Cardiovascular Ejection fraction at least 45% Pulmonary Clinically normal pulmonary function (patients 5 years of age and under) FEV_1 and FVC at least 50% (patients over 5 years of age) OR Arterial blood gas normal and DLCO greater than 50% Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No mucositis or mucosal infection HIV negative PRIOR CONCURRENT THERAPY: Biologic therapy Not specified Chemotherapy At least 3 weeks since prior systemic cytotoxic chemotherapy Endocrine therapy Not specified Radiotherapy At least 6 months since prior radiotherapy to the pelvis or spine Surgery Not specified