Thiotepa and Radiation Therapy in Treating Young Patients With Newly Diagnosed Malignant Brain Tumors

OBJECTIVES: Primary * Determine tumor response to adjuvant thiotepa followed by radiotherapy in pediatric patients with newly diagnosed malignant astrocytic tumors. Secondary * Determine the acute and chronic toxicity of thiotepa in these patients. * Determine the variability in thiotepa metabolism by measuring plasma and cerebrospinal fluid pharmacokinetics of thiotepa and tepa in these patients. * Develop a phase II study framework model, to determine the chemosensitivity to new, single-agent regimens in the treatment of high-grade (malignant) astrocytic tumors, including anaplastic astrocytoma, glioblastoma, giant cell glioblastoma, and gliosarcoma. * Determine the incidence of distant neuraxial metastases in patients at the time of relapse. * Determine the 1-year disease-free survival rate in patients treated with this regimen. OUTLINE: This is a multicenter study. Patients are stratified by age (3-15 vs 16-20 years of age). * Chemotherapy: Patients receive thiotepa IV continuously over 168 hours on days 1-7. Treatment repeats every 28 days for up to 2 courses. Patients then proceed to radiotherapy after blood counts recover. * Radiotherapy: Patients undergo external-beam radiotherapy once daily, 5 days a week, for approximately 6 weeks. * Post-radiation chemotherapy: Patients with complete, partial, or objective response, or stable disease after 2 courses of thiotepa may receive thiotepa alone for up to 8 more courses at the discretion of the treating physician. After completion of study treatment, patients are followed periodically. PROJECTED ACCRUAL: A total of 30 patients will be accrued for this study.