Temozolomide and O6-Benzylguanine in Treating Children With Recurrent Brain Tumors

Inclusion Criteria:

* Recurrent or refractory pediatric brain tumors; a histopathologic diagnosis from either the initial presentation or at the time of recurrence is required for all but brain stem gliomas
* Karnofsky or Lansky ≥ 60%
* Life expectancy \> 8 weeks
* Patients with neurological deficits should have deficits that are stable for a minimum of 1 week prior to study entry
* Chemotherapy: No more than 2 previous chemotherapy/biologic therapy regimens; evidence of recovery from prior chemotherapy/biologic therapy; no myelosuppressive chemotherapy within 3 weeks (6 weeks if a nitrosourea agent) of study entry; patients who have received temozolomide are eligible if they have not received the drug in the past 3 months and did not experience any non-hematopoietic Grade 3/4 toxicity with prior temozolomide therapy
* XRT: ≥ 3 months prior to study entry for craniospinal irradiation (≥ 18 Gy); ≥ 4 weeks for local radiation to primary tumor; and ≥ 2 weeks prior to study entry for focal irradiation to symptomatic metastatic sites
* Bone Marrow Transplant: ≥ 6 months prior to study entry
* Anti-convulsants: Patients will be eligible for this study even if they are receiving anti-convulsants
* Growth factors: Off all colony forming growth factor(s) \> 2 weeks prior to study entry (G-CSF, GM-CSF, Erythropoietin)
* Dexamethasone: Patients who are receiving dexamethasone must be on a stable dose for at least 1 week prior to study entry
* ANC \> 1,000/μl
* Platelets \> 100,000/μl
* Hemoglobin \> 8g/dl
* Patients may have bone marrow involvement by disease; platelet and Hgb counts must be transfusion independent
* Creatinine ≤ 1.5 times institutional normal for age
* Or GFR \> 70 ml/min/1.73m\^2
* Bilirubin ≤ upper limit of normal for age
* SGPT (ALT) \< and SGOT (AST) \< 2.5X institutional normal
* No overt renal, hepatic, cardiac or pulmonary disease
* Female patients of childbearing potential must have negative serum or urine pregnancy test; patient must not be pregnant or breast-feeding; while no known teratogenic effects are known for O6-BG so far, there is little data to address this specifically; as such, the prudent approach is to exclude pregnant and breastfeeding patients until further data is available
* Patients of childbearing or child-fathering potential must be willing to use a medically acceptable form of birth control, which includes abstinence, while being treated on this study
* Signed informed consent according to institutional guidelines must be obtained and patients must begin therapy within seven (7) days of registration

Exclusion Criteria:

* Patients must not be receiving any other anticancer or experimental drug therapy
* Patients with a history of hypersensitivity to dacarbazine, temozolomide or polyethylene glycol are excluded