DISEASE CHARACTERISTICS:

• Histologically confirmed stage I-IV primary central nervous system lymphoma for which no curative therapy exists
• Measurable tumor by MRI or CT scan
• Tumor must be greater than 2 cm in largest diameter

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 60-100%

Life expectancy:

• At least 2 months

Hematopoietic:

• WBC greater than 2,000/mm^3
• Platelet count greater than 50,000/mm^3

Hepatic:

• Bilirubin no greater than 2.5 mg/dL
• SGOT and SGPT no greater than 5 times upper limit of normal
• No hepatic insufficiency

Renal:

• Creatinine no greater than 2.5 mg/dL
• No history of renal conditions that contraindicate high dosages of sodium

Cardiovascular:

• No cardiac insufficiency
• No hypertension
• No history of congestive heart failure
• No history of other cardiovascular conditions that contraindicate high dosages of sodium

Other:

• Not pregnant or nursing
• Fertile patients must use effective contraception during and for at least 4 weeks after study participation
• No serious infection requiring antibiotics, antifungals, or antivirals

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 4 weeks since prior immunotherapy and recovered
• No concurrent immunomodulatory agents (e.g., interferon or interleukin-2)

Chemotherapy:

• At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas) and recovered
• No concurrent antineoplastic agent

Endocrine therapy:

• Concurrent corticosteroids allowed
• Must be on stable dose for at least 4 weeks prior to study entry

Radiotherapy:

• At least 8 weeks since prior radiotherapy and recovered

Surgery:

• Not specified

Other:

• No prior antineoplastons