Inclusion Criteria

DISEASE CHARACTERISTICS:

- B-cell non-Hodgkin lymphoma (NHL) involving the brain, as demonstrated by contrasted
MRI and histologic confirmation by one of the following within 6 weeks prior to
registration:

- A positive cerebral spinal fluid (CSF) cytology for lymphoma or a monoclonal
lymphocyte population as defined by cell surface markers

- A biopsy of the vitreous or uvea demonstrating NHL

- Brain biopsy

- Patients in whom the type of lymphoma could not be determined or is unknown
(e.g., not enough tissue for further analysis) are assumed to have a B-cell
lymphoma and are eligible

- Patient must agree to submit tissue (i.e., the original H/E-stained slides and
immunohistochemistry studies) for central pathology review post-registration

- No evidence of systemic NHL as demonstrated by a CT scan of the chest, abdomen, and
pelvis within 6 weeks prior to registration

- Bone marrow biopsy is not required for registration but must be obtained prior
to start of treatment

PATIENT CHARACTERISTICS:

- History and physical examination within 6 weeks of registration

- Karnofsky performance status (KPS) equal to 50% or higher, with the following
exception:

- KPS 30% to 50% are eligible if the reason for the poor performance status is
neurologic deficit from primary central nervous system (CNS) lymphoma

- Patients with KPS 30% to 50% due to reasons other than primary CNS lymphoma
are ineligible

- Patients with KPS under 30% for any reason are ineligible

- Absolute neutrophil count (ANC) ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Hemoglobin (Hgb) ≥ 8.0 g/dL (transfusion or other intervention to achieve Hgb ≥ 8.0
g/dL is acceptable)

- Bilirubin < 2.0 mg/dL

- Aspartate aminotransferase (AST) < 2.5 times upper limit of normal

- Serum creatinine < 1.5 mg/dL

- Calculated creatinine clearance (CrCl) > 50 cc/min (CrCl from a 24-hour urine
collection may also be used)

- Women of childbearing potential and male participants must agree to practice adequate
contraception during therapy

- Patient must be able to swallow pills

- Patient must have documentation of negative HIV-1 testing within 6 weeks prior to
study registration

- No prior invasive malignancy (except non-melanomatous skin cancer) unless disease
free for a minimum of 3 years (for example, carcinoma in situ of the breast, oral
cavity, or cervix are all permissible)

- No severe, active co-morbidity, defined as follows:

- Unstable angina and/or congestive heart failure requiring hospitalization within
the last 6 months

- Transmural myocardial infarction within the last 6 months

- Acute bacterial or fungal infection requiring intravenous antibiotics at the
time of registration

- Chronic obstructive pulmonary disease exacerbation or other respiratory illness
requiring hospitalization or precluding study therapy within 30 days before
registration

- Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects

- Laboratory tests for liver function and coagulation parameters are not
required for entry into this protocol

- Known pre-existing immunodeficiency as seen in organ transplant recipient

- No prior allergic reaction to any of the study drugs involved in this protocol

PRIOR CONCURRENT THERAPY:

- No prior treatment with chemotherapy for CNS lymphoma

- Prior chemotherapy for a different cancer is allowable

- No prior cranial irradiation

- No concurrent intensity-modulated radiotherapy