Inclusion Criteria

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