DISEASE CHARACTERISTICS:

• Histologically confirmed non-Hodgkin's lymphoma by brain biopsy

• Patients with inconclusive biopsy or patients who are not candidates for biopsy must have typical CT scan or MRI of the brain AND meet ≥ 1 of the following criteria:

  • Positive cerebrospinal fluid cytology for lymphoma OR a monoclonal lymphoid population as defined by cell surface markers or immunoglobulin gene rearrangement studies
  • Biopsy-proven involvement of the vitreous or uvea if cells are apparent in the posterior chamber or vitreous by ophthalmological examination

• Bideminsionally measurable disease, defined as contrast-enhancing tumor ≥ 1 cm by pretreatment MRI/CT scan

  • Meningeal or vitreous involvement constitutes evaluable but not measurable disease
  • If an excisional, rather than a needle biopsy was done, measurable disease must be present on a postoperative scan
  • PET-CT scan not allowed
• No systemic lymphoma (as determined by pre-registration CT scans and physical examination)

PATIENT CHARACTERISTICS:

• ECOG performance status 0-3
• Absolute granulocyte count ≥ 1,500/mm³
• Platelet count ≥ 100,000/mm³
• Bilirubin ≤ upper limit of normal (ULN)
• SGOT ≤ 2.0 times ULN
• Creatinine clearance ≥ 50 mL/min
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No HIV-1 positivity
• No other malignancy within the past 5 years except basal cell skin cancer or any carcinoma in situ
• No pre-existing immunodeficiency
• No hepatitis B surface antigen positivity

PRIOR CONCURRENT THERAPY:

• No prior chemotherapy or radiotherapy for primary central nervous system lymphoma
• No prior organ or bone marrow transplantation