The initial 5-FU dosage will be 500 mg/m^2 administered on day 1 of course 1. We plan to treat a maximum of 3 cohorts of research participants (dosage levels - 0, 1, and 2) with escalating doses of 5-FU. A cycle is defined as 42 days. The first 6 weeks of therapy will constitute the dose-limiting toxicity (DLT) evaluation period.~Primary objective~To investigate the safety and pharmacokinetics (plasma and cerebrospinal fluid) of weekly bolus dose 5-FU in children and young adults with recurrent/refractory ependymoma~To study the safety of 500 mg/m^2 weekly bolus dose 5-FU in less-heavily pre-treated children and young adults with recurrent/refractory ependymoma.~Secondary objectives~To document and describe toxicities associated with 5-FU administered on a weekly bolus schedule~To document preliminary antitumor activity in participants with recurrent or refractory ependymoma treated with 5-FU~To assess the feasibility of measuring expression level of Thymidylate Synthetase (TYMS) in formalin fixed paraffin embedded (FFPE) tumor samples using the Quantigene assay~To evaluate the association between specific genetic polymorphisms (e.g., DPYD) and the pharmacokinetics of 5-FU
This is a phase I study to investigate the safety and pharmacokinetics of weekly 5-fluorouracil (5-FU) administered as a bolus dose in children and young adults with recurrent or refractory ependymoma. The results from this study will inform a subsequent phase II St. Jude investigator-initiated trial.