Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed initial diagnosis of malignant solid tumor
refractory to conventional therapy or for which no effective therapy exists

- Brain tumors allowed if not on anticonvulsants

- Brainstem gliomas allowed without histologic diagnosis

- Solid lymphomas allowed

- No bone marrow involvement

PATIENT CHARACTERISTICS:

Age:

- 1 to 21

Performance status:

- Karnofsky 50-100% if over 10 years of age

- Lansky 50-100% if 10 years of age and under

Life expectancy:

- At least 8 weeks

Hematopoietic:

- Absolute neutrophil count at least 1,000/mm^3

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 8 g/dL (transfusion allowed)

Hepatic:

- Bilirubin no greater than 1.5 mg/dL

- ALT less than 5 times normal

- Albumin at least 2 g/dL

Renal:

- Creatinine normal for age OR

- Glomerular filtration rate normal for age

Other:

- No uncontrolled infection

- No other significant systemic illness

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 1 week since prior biologic therapy and recovered

- At least 1 week since prior growth factors

- No prior stem cell transplantation

Chemotherapy:

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

- No more than 2 prior chemotherapy regimens

- No other concurrent cancer chemotherapy

Endocrine therapy:

- Concurrent dexamethasone allowed in patients with CNS tumors provided dose is stable
or decreasing for at least 2 weeks prior to study

Radiotherapy:

- Recovered from prior radiotherapy

- At least 2 weeks since prior local palliative radiotherapy (small port)

- No prior substantial bone marrow radiotherapy

- No prior central axis radiotherapy

- No concurrent radiotherapy

Surgery:

- Not specified

Other:

- No concurrent anticonvulsants

- No other concurrent anticancer therapy or investigational agents