Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically proven (except for brain stem tumors) malignancy
that has

failed or relapsed after standard first-line antineoplastic therapy

- Sarcoma (soft tissue and bone)

- Kidney tumors

- Brain tumors

- Other solid tumors (gonadal and germ cell tumors, malignant melanoma,

- retinoblastoma, liver tumors, and miscellaneous tumors) Must have had recurrence
within the past 4 weeks

No bone marrow involvement

No prior or concurrent myelogenous leukemia

PATIENT CHARACTERISTICS:

Age:

- 1 to 21

Performance status:

- Lansky or Karnofsky 60-100%

Life expectancy:

- At least 12 weeks

Hematopoietic:

- Absolute neutrophil count greater than 1000/mm3

- Platelet count greater than 100,000/mm3

- No grade III or IV thrombosis

Hepatic:

- Bilirubin less than 1.5 times upper limit of normal (ULN)

- SGOT or SGPT less than 2.5 times ULN

Renal:

- Creatinine clearance or glomerular filtration rate at least 70 mL/min

Cardiovascular:

- Ejection fraction normal

- No evidence of arrhythmias requiring therapy

- Fractional shortening greater than 28%

Other:

- Not pregnant or nursing

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 10 days since prior colony-stimulating factor therapy and recovered

- At least 30 days since prior epoetin alfa

- No other concurrent cytokines, including epoetin alfa

Chemotherapy:

- At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas) and

- recovered

- At least 3 months since therapy with etoposide, carboplatin, or ifosfamide

- that is identical to study treatment

Endocrine therapy:

- Not specified

Radiotherapy:

- Concurrent radiotherapy allowed after third course of therapy

- No prior cranial/spinal radiotherapy

- No prior radiotherapy to greater than 50% of bone marrow

Surgery:

- Concurrent surgery allowed after the second course of therapy

Other:

- No concurrent investigational agents

- No concurrent lithium, aspirin, coumadin, or heparin