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