DISEASE CHARACTERISTICS:

• Histologically confirmed solid tumor refractory to standard therapy and for which no potentially curative therapy exists, including, but not limited to:

  • Rhabdomyosarcoma and other soft tissue sarcomas
  • Ewing's family of tumors
  • Osteosarcoma
  • Neuroblastoma
  • Wilms' tumor
  • Hepatic tumors
  • Germ cell tumors
  • Primary brain tumor
• Histological confirmation may be waived for brainstem or optic gliomas
• Measurable or evaluable disease
• Evidence of progressive disease on prior chemotherapy or radiotherapy or persistent disease after prior surgery

PATIENT CHARACTERISTICS:

Age:

• 21 and under

Performance status:

• ECOG 0-2

Life expectancy:

• At least 8 weeks

Hematopoietic:

• Absolute granulocyte count greater than 1,500/mm^3
• Hemoglobin greater than 8 g/dL
• Platelet count greater than 100,000/mm^3

Hepatic:

• Bilirubin normal
• SGPT less than 2 times upper limit of normal
• No significant hepatic dysfunction

Renal:

• Creatinine normal OR
• Creatinine clearance at least 60 mL/min

Cardiovascular:

• No significant cardiac dysfunction

Pulmonary:

• No significant pulmonary dysfunction

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Able to swallow capsules
• No significant unrelated systemic illness that would preclude study (e.g., serious infections or organ dysfunction)
• No prior hypersensitivity to dacarbazine, temozolomide, or polyethylene glycol

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 1 week since prior colony-stimulating factors (e.g., filgrastim [G- CSF], sargramostim [GM-CSF], or epoetin alfa)
• At least 4 months since prior myeloablative therapy requiring bone marrow or stem cell transplantation
• No concurrent anticancer immunotherapy

Chemotherapy:

• See Disease Characteristics
• At least 3 weeks since prior chemotherapy (4 weeks for nitrosoureas) and recovered
• Prior temozolomide allowed provided not administered within past 3 months, no severe toxicities experienced during prior course, and not given in combination with other agents designed to inactivate alanine-glyoxylate aminotransferase
• No other concurrent investigational or standard anticancer chemotherapy

Endocrine therapy:

• Concurrent corticosteroids for control of brain tumor-associated edema allowed provided on stable or decreasing dose for at least 1 week prior to study

Radiotherapy:

• See Disease Characteristics
• At least 4 weeks since prior limited-field radiotherapy
• At least 4 months since prior craniospinal irradiation, total body irradiation, or radiotherapy to more than half of the pelvis
• Recovered from prior radiotherapy
• No concurrent anticancer radiotherapy

Surgery:

• See Disease Characteristics

Other:

• At least 4 weeks since other prior investigational therapy and recovered
• No other concurrent anticancer investigational agents