Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed Ewing's sarcoma or primitive neuroectodermal tumor (PNET)

- Disease that has recurred or not responded despite prior therapy

- Has declined enrollment on or is not eligible for clinical trial COG-AEWS0521

- Must have at least one site of measurable disease involving lung or soft tissue as
documented by CT scan and/or MRI

- No disease limited to bone

PATIENT CHARACTERISTICS:

- Karnofsky performance status (PS) 50-100% (for patients > 16 years of age) OR Lansky
PS 50-100% (for patients ≤ 16 years of age)

- Life expectancy ≥ 8 weeks

- ANC ≥ 750/mm^3

- Platelet count ≥ 75,000/mm^3 (50,000/mm^3 if documented bone marrow metastatic
disease) (transfusion independent)

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

- Bilirubin ≤ 1.5 times upper limit of normal (ULN) for age and < 2.0 mg/dL

- ALT ≤ 2.5 times ULN

- Creatinine clearance or radioisotope GFR ≥ 70 mL/min OR creatinine meeting the
following criteria:

- ≤ 0.4 mg/dL (1 month to < 6 months of age)

- ≤ 0.5 mg/dL (6 months to < 1 year of age)

- ≤ 0.6 mg/dL (1 to < 2 years of age)

- ≤ 0.8 mg/dL (2 to < 6 years of age)

- ≤ 1.0 mg/dL (6 to < 10 years of age)

- ≤ 1.2 mg/dL (10 to < 13 years of age)

- ≤ 1.4 mg/dL (≥ 13 years of age) (female)

- ≤ 1.5 mg/dL (13 to < 16 years of age) (male)

- ≤ 1.7 mg/dL (≥ 16 years of age) (male)

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No uncontrolled infection, including systemic fungal infections requiring ongoing
antifungal therapy

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- Recovered from all prior tumor-directed therapy

- At least 7 days since prior biologic therapy or immunotherapy

- At least 1 week since prior hematopoietic growth factors (2 weeks for pegfilgrastim)

- At least 2 weeks since prior myelosuppressive chemotherapy

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

- At least 6 weeks since prior substantial bone marrow radiotherapy

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

- At least 6 months since prior autologous stem cell transplantation

- No prior allogeneic stem cell transplantation

- No prior cytarabine

- No other concurrent investigational agents, including chemotherapy, immunotherapy, or
biologic therapy

- No other concurrent anticancer chemotherapy or immunomodulating agents

- Concurrent corticosteroids allowed

- No concurrent intrathecal chemotherapy

- Concurrent radiotherapy to localized painful lesions allowed provided at least one
measurable lesion is not irradiated (no irradiated lesion may be used to assess tumor
response)