Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologic or tumor marker confirmation of malignancy at original diagnosis

- Neoplastic meningitis/leptomeningeal metastasis refractory to conventional therapy
and other therapies of higher priority, defined as:

- Stratum A:

- Small non-cleaved lymphoma (Burkitt's) with any L-3 blast in cerebrospinal
fluid (CSF)

- Any other lymphoma or leukemia with CSF cell count greater than 5/mm3 AND
evidence of blast cells by cytology or cytospin preparation OR

- Stratum B:

- Solid tumor or other malignancy with presence of tumor cells on cytospin OR
positive cytology OR neuroimaging evidence of leptomeningeal tumor by MRI
or CT myelogram

- No leptomeningeal leukemia or lymphoma with concurrent bone marrow relapse

- No clinical evidence of untreated obstructive hydrocephalus or compartmentalization
of the CSF

PATIENT CHARACTERISTICS:

Age:

- 65 and under

Performance status:

- Lansky 50-100% (age 16 and under)

- Karnofsky 50-100% OR ECOG 0-3 (over age 16)

Life expectancy:

- At least 2 months

Hematopoietic:

- Stratum B:

- Absolute neutrophil count at least 750/mm^3

- Platelet count at least 75,000/mm^3 (transfusion independent)

- Hemoglobin at least 10.0 g/dL (red blood cell transfusions allowed)

Hepatic:

- Bilirubin no greater than 1.5 times normal

- SGOT or SGPT less than 2.5 times upper limit of normal

Renal:

- Creatinine no greater than 1.5 mg/dL OR

- Creatinine clearance or radioisotope glomerular filtration rate at least 70 mL/min

Neurologic:

- Seizures allowed if well controlled and on anticonvulsants

- CNS toxicity no greater than grade 2

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No uncontrolled infections

- HIV allowed

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent immunomodulating agents (stratum B)

- No stem cell transplantation (stratum A)

Chemotherapy:

- At least 2 weeks since prior chemotherapy (4 weeks for nitrosoureas)

- No other concurrent cancer chemotherapy (stratum B)

- Other concurrent systemic cancer chemotherapy for leukemia or lymphoma allowed with
the following restrictions:

- No oral or IV topotecan

- No moderate or high-dose IV or subcutaneous cytarabine (greater than 1.0 g/m2
per day)

- No moderate or high-dose IV methotrexate (greater than 1 g/m2 per day)

- No IV thiotepa

- No myeloablative chemotherapy

- No intrathecal or intraventricular chemotherapy

Endocrine therapy:

- Concurrent corticosteroids allowed only for treatment of increased intracranial
pressure in patients with CNS tumors

- No concurrent intrathecal or intraventricular hydrocortisone

Radiotherapy:

- At least 4 weeks since completion of radiotherapy to the brain or spine and recovered

- Concurrent radiotherapy to localized painful lesions producing acute neurologic
dysfunction allowed provided at least 1 measurable lesion is not irradiated

- No concurrent craniospinal or whole-brain radiotherapy

Surgery:

- Not specified

Other:

- Recovered from prior therapy

- At least 7 days since prior investigational drug

- No other concurrent intrathecal or intraventricular therapy for leptomeningeal
disease