Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed malignancy refractory to conventional therapy or for which
no conventional therapy exists

- Histologic confirmation not required for brain stem tumors

- Concurrently on anticonvulsants at a steady level for at least 2 weeks

PATIENT CHARACTERISTICS:

Age:

- 1-21 years old

Performance status:

- Karnofsky 50-100% (over 10 years of age)

- Lansky 50-100% (10 years of age or under)

Life expectancy:

- At least 8 weeks

Hematopoietic:

- Neutrophil count at least 1,000/mm3

- Platelet count at least 100,000/mm3 (transfusion independent)

- Hemoglobin at least 8.0 g/dL (red blood cell transfusions allowed)

Hepatic:

- Bilirubin no greater than 1.5 times normal for age

- SGPT less than 5 times normal for age

- Albumin at least 2 g/dL

Renal:

- Creatinine no greater than 1.5 times normal for age OR

- Creatinine clearance or radioisotope glomerular filtration rate at least lower limit
of normal for age

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No uncontrolled infection

- No evidence of active graft-vs-host disease

- Neurologic deficits for CNS tumors stable for at least 2 weeks prior to study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 1 week since prior antineoplastic biologic therapy

- At least 6 months since prior allogeneic stem cell transplantation

- At least 1 week since prior growth factors

- No concurrent sargramostim (GM-CSF)

- No concurrent prophylactic growth factors during first course of study therapy

- Recovered from prior immunotherapy

Chemotherapy:

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

Endocrine therapy:

- Concurrent dexamethasone for CNS tumors with increased intracranial pressure allowed
if dose stable or decreasing for at least 2 weeks prior to study

Radiotherapy:

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

- At least 6 months since prior craniospinal radiotherapy

- At least 6 months since prior radiotherapy to at least 50% of pelvis

- At least 6 weeks since prior substantial bone marrow radiotherapy

- Recovered from prior radiotherapy

Surgery:

- Not specified

Other:

- No other concurrent investigational agent