OUTLINE: Patients with surgically approachable lesions undergo maximal surgical debulking that allows preservation of good neurologic functioning. Harvest: Patients receive filgrastim (G-CSF) subcutaneously or IV beginning 4 days prior to initiation of first leukapheresis and continuing until completion of harvest. Peripheral blood stem cells are harvested and selected for CD34+ cells which are transduced with a fibronectin assisted retroviral vector expressing human O6-methylguanine DNA methyltransferase. Intensification: Patients receive oral lomustine and vincristine IV on day 0 and oral procarbazine on days 1-7. Treatment repeats every 4 weeks for 4 courses in the absence of disease progression or unacceptable toxicity. Patients with newly diagnosed tumors may undergo involved field radiotherapy (IF-RT) after completion of the third course of chemotherapy and may begin the fourth course of chemotherapy after completion of IF-RT. Transplantation: Two-thirds of the transduced CD34+ cells are reinfused on day 9 of the first course of chemotherapy. The remaining portion (one-third) of the transduced CD34+ cells are reinfused on day 9 of the second course of chemotherapy. Untransduced CD34+ cells are reinfused on day 9 of the last 3 courses of chemotherapy. Patients are followed every 3 months for 6 months, every 4 months for 1 year, every 6 months through year 5, and then annually thereafter.