O6-Benzylguanine and Temozolomide in Treating Young Patients With Recurrent or Progressive Gliomas or Brain Stem Tumors

INCLUSION CRITERIA Tumor: Participants must have a high-grade glioma (including e.g. histologically confirmed anaplastic astrocytoma, glioblastoma multiforme, anaplastic oligodendroglioma, anaplastic ganglioma, gliosarcoma) or a brainstem tumor (histologic confirmation waived) with documentation of disease recurrence or progression after treatment with standard therapy. Participants must have bi-dimensionally measurable disease, defined as at least 1 lesion that can be measured in ≥ 2 dimensions Age: 21 years of age or less Performance status: Karnofsky 60-100% (for patients > 16 years of age) or Lansky 60-100% (for patients ≤ 16 years of age) Life expectancy: Not specified Hematopoietic: Must have adequate bone marrow function defined as absolute neutrophil count > 1,500/mm^3, platelet count > 100,000/mm^3 (unsupported), hemoglobin > 8 g/dL (may be supported), and absolute lymphocyte count ≥ 500/mm^3 Hepatic: Must have SGOT and SGPT ≤ 2.5 times upper limit of normal (ULN), bilirubin ≤ 1.5 times ULN, and no overt hepatic disease Renal: Participants must have creatinine clearance ≥ 60 mL/min or creatinine based on age as follows: no greater than 0.8 mg/dL (for patients ≤ 5 years of age), no greater than 1.0 mg/dL (for patients 6 to 10 years of age), no greater than 1.2 mg/dL (for patients 11 to 15 years of age), or no greater than 1.5 mg/dL (for patients > 15 years of age). There must be no overt renal disease Cardiovascular: Must have no overt cardiac disease Pulmonary: Must have no overt pulmonary disease Other: Female participants of childbearing potential must have a negative pregnancy test prior to study registration, and must avoid breast-feeding. Female and male participants of childbearing or child-fathering potential must use effective contraception Bone Marrow Transplant: Must be at least 6 months since prior allogeneic bone marrow transplantation and at least 3 months since prior autologous bone marrow or stem cell transplantation Growth Factors: Must be at least 2 weeks since prior colony-stimulating factors (e.g., filgrastim [G-CSF], sargramostim [GM-CSF], or erythropoietin) Prior Chemotherapy: Must have received last dose of myelosuppressive anticancer chemotherapy ≥ 3 weeks prior to study registration and ≥ 6 weeks for nitrosoureas. Must have received last dose of nonmyelosuppressive investigational agents or anticancer drugs ≥ 7 days prior to study registration. Participants who have received prior temozolomide are eligible Concurrent Endocrine Therapy: Concurrent corticosteroid therapy is allowed Prior Radiotherapy: Must have received last fraction of craniospinal irradiation and local irradiation to the primary tumor ≥ 12 weeks prior to study registration Prior Therapy-Other: Must have recovered from all prior therapy EXCLUSION CRITERIA Must not have history of severe toxicity (≥ grade 3) associated with temozolomide Must not be receiving other concurrent anticancer or investigational therapy Must not have history of hypersensitivity to dacarbazine, temozolomide, or polyethylene glycol (PEG) Must not have uncontrolled significant systemic illness including infection, or overt renal, hepatic, cardiac, or pulmonary disease Must not be HIV positive