Inclusion Criteria

Disease Characteristics:

Histologically proven cancer that is refractory to standard therapy.

Patients with neurofibromatosis having progressive inoperable plexiform neurofibromas with
potential to cause significant morbidity are eligible.

Patients with brainstem gliomas histology may have histology requirements waived.

Patients without prior therapy are eligible if they have diseases with no available
standard therapy.

Patients with evidence of bone marrow involvement by tumor, or a history of either bone
marrow transplantation or extensive radiotherapy will be eligible, but inevaluable for
hematologic toxicities.

Patients with greater than grade 2 neurocortical toxicity will be excluded.

PRIOR/CONCURRENT THERAPY:

Biologic Therapy: No concurrent hematopoietic growth factor.

Chemotherapy: No chemotherapy within 3 weeks of study.

No nitrosoursea within 6 weeks of study.

No concurrent chemotherapy allowed.

Must be on stable or decreasing dose of dexamethasone within 2 weeks of study.

Endocrine Therapy: Not specified.

Radiotherapy: No radiotherapy within 6 weeks of study.

Surgery: Not specified.

Other:

Patient must be recovered from toxic effects of all prior therapy.

Concurrent antibiotic therapy when appropriate.

Patient Characteristics:

Age: 2 to 21.

Performance Status: ECOG 0-2.

Life Expectancy: At least 8 weeks.

Hematopoietic (hematologic requirements below do not apply to patients with histologically
confirmed bone marrow involvement or history of either bone marrow transplantation or
extensive radiotherapy; these patients are inevaluable for hematologic toxicity):

Absolute granulocyte count (AGC) at least 1500/mm3.

Platelet count at least 100,000/mm3.

Hemoglobin at least 8 g/dL.

Hepatic:

Bilirubin no greater than 2 mg/Dl.

SGPT less than 2 times normal.

Renal:

Creatinine no greater than 1.5 mg/Dl OR

Creatinine clearance at least 60 Ml/min/square meter.

Other:

No systemic illness.

Not pregnant or nursing.

No amino acidurias or organic acidemias.