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)