Valproic Acid in Treating Young Patients With Recurrent or Refractory Solid Tumors or CNS Tumors

DISEASE CHARACTERISTICS:

• Histologically confirmed* malignant solid tumor, including CNS tumors, at original diagnosis or relapse
• Recurrent or refractory disease NOTE: *Histologic confirmation not required for intrinsic brain stem or optic pathway tumors
• Measurable or evaluable disease, defined by 1 of the following criteria:
• Any unidimensionally measurable lesion ≥ 10 mm by standard MRI or CT scan for either solid or CNS tumors
• At least 1 nonmeasurable lesion that is evaluable by nuclear medicine, immunocytochemistry, tumor markers, cerebrospinal fluid cytology, or other reliable measures
• No known curative therapy exists
• No documented tumor involvement in the bone marrow

PATIENT CHARACTERISTICS:

Age

• 2 to 21

Performance status*

• Lansky 50-100% (for patients ≤ 10 years of age)
• Karnofsky 50-100% (for patients > 10 years of age)

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count ≥ 1,000/mm^3
• Platelet count ≥ 100,000/mm^3 (transfusion independent)
• Hemoglobin ≥ 8.0 g/dL (transfusions allowed)

Hepatic

• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• ALT ≤ 110 (ULN for this study is 45 U/L)
• Albumin ≥ 2 g/dL

Renal

• Creatinine clearance or radioisotope glomerular filtration rate ≥ 70 mL/min OR
• Creatinine based on age as follows:
• No greater than 0.8 mg/dL (for patients ≤ 5 years of age)
• No greater than 1.0 mg/dL (for patients 6 to 10 years of age)
• No greater than 1.2 mg/dL (for patients 11 to 15 years of age)
• No greater than 1.5 mg/dL (for patients over 15 years of age)

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Neurologic deficits in patients with CNS tumors must be stable for ≥ 1 week before study entry
• No uncontrolled infection
• No known urea cycle disorders or other metabolic disorders
• No other condition that would preclude study compliance

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Recovered from prior immunotherapy
• At least 7 days since prior hematopoietic growth factors that support platelet or WBC number or function
• At least 7 days since prior antineoplastic biologic agents
• At least 3 months since prior stem cell transplantation or rescue without total body irradiation
• No evidence of active graft vs host disease
• No other concurrent anticancer biologic therapy or immunotherapy

Chemotherapy

• More than 3 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosoureas) and recovered
• No other concurrent anticancer chemotherapy

Endocrine therapy

• Patients with CNS tumors must be on a stable or decreasing dose of dexamethasone for the past 7 days

Radiotherapy

• See Biologic therapy
• Recovered from prior radiotherapy
• At least 6 months since prior total body irradiation, craniospinal radiotherapy, or radiotherapy to ≥ 50% of the pelvis
• At least 6 weeks since other prior substantial bone marrow radiotherapy
• At least 2 weeks since prior local palliative small port radiotherapy
• No concurrent anticancer radiotherapy

Surgery

• Not specified

Other

• No other concurrent investigational agents
• No other concurrent anticancer agents
• No other concurrent anticonvulsants
• Patients receiving valproic acid (VPA) before study entry must have a total trough VPA concentration < 100 mcg/mL within the past 7 days