Valproate and Etoposide for Patients With Neuronal Tumors and Brain Metastases

Primary Objective: * Determine the interindividual range and median of individual maximum tolerated doses of valproic acid administered as one time evening dose in conjunction with a dose oral etoposide (50 mg/m2/day for children, but only 25mg/m2/day for adults to start) for four different age groups. Secondary Objectives: * Determine the qualitative and quantitative toxicity and reversibility of toxicity of valproic acid in conjunction with oral etoposide, * To investigate the clinical pharmacokinetics of valproic acid when given in conjunction with oral etoposide, * To describe quality of life of patients with relapsed, or progressive central and peripheral nervous system tumors when treated with oral valproic acid and etoposide, * To observe and describe the response pattern of progressive central nervous system tumors treated with oral valproic acid and etoposide, * To observe and describe event free survival time and overall survival time of patients with relapsed, or progressive central nervous system tumors when treated with oral valproic acid and etoposide, * To determine if histone deacetylase activity and topoisomerase expression in lymphocytes of patients is related to valproic acid levels, and * To determine, if the individual maximal tolerated dose (iMTD) depends on the initial performance status of the patient in the beginning of the treatment.