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