DISEASE CHARACTERISTICS: Primary central nervous system non-Hodgkin's lymphoma (PCNSL) Clinically diagnosed intracranial space-occupying lesion Pathology consistent with non-Hodgkin's lymphoma and reviewed by NCCTG Biopsy optional if characteristic history, pathognomonic neuroimaging, and cytology are consistent with malignant lymphocytes from vitrectomy, CSF, or both No occult systemic lymphoma or prior lymphoma No post-transplant lymphoproliferative disorder Disease measurable or evaluable on postoperative contrast-enhanced CT or MRI Postoperative therapy must start within 6 weeks of definitive diagnosis

PATIENT CHARACTERISTICS: Age: 18 to 70 Performance status: ECOG 0-3 Hematopoietic: WBC at least 4,000/mm3 Platelet count at least 120,000/mm3 Hepatic: Bilirubin no greater than 2 times normal AST no greater than 2 times normal Renal: Creatinine no greater than 1.5 times normal Cardiovascular: No heart failure No uncontrolled arrhythmia Pulmonary: No severe pulmonary failure Other: No serious uncontrolled infection No active bleeding No AIDS or HIV-positive serology No prior organ transplant No pregnant or nursing women Negative pregnancy test required of fertile women Adequate contraception required of fertile patients

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy Endocrine therapy: Corticosteroids allowed if dose fixed or decreasing for at least 1 week prior to baseline scan Radiotherapy: No prior radiotherapy Surgery: Not specified