Cytarabine in Treating Young Patients With Recurrent or Refractory Ewing's Sarcoma

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)