Topotecan in Treating Patients With Recurrent, Progressive, or Refractory Cancer That is Metastatic to the Lining Around the Brain

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