A Pilot Study Evaluating 18F-L-Thymidine (FLT) PET Imaging in Children With Gliomas

BACKGROUND: * A limitation of current investigational therapy for patients with brain tumors is assessment of response. * (18)F-FDG PET is commonly used to assess tumor metabolism. However, normal brain uses glucose as an energy source, resulting in increased background FDG uptake, which confounds results and makes it difficult to distinguish normal from neoplastic activity. * Newer imaging techniques that noninvasively assess metabolic and physiologic characteristics of brain tumor tissue are being developed to identify biomarkers of clinical efficacy in trials of new molecularly targeted agents. * (18)F-fluorothymidine (FLT) is a PET radiopharmaceutical that is taken up by proliferating cells and may therefore serve as a surrogate marker of early response or lack of response to treatment. * This study will prospectively evaluate (18)F-FLT in children undergoing radiation therapy for gliomas. OBJECTIVES: Primary objectives: * Determine the feasibility of (18)F-FLT PET imaging in pediatric patients with malignant gliomas * Determine the ability of (18)F-FLT PET imaging to detect treatment changes in pediatric patients with malignant gliomas undergoing radiation therapy Secondary objectives: * Determine the safety and toxicity profile of PET imaging using (18)F-FLT in pediatric patients with malignant gliomas * To correlate changes in (18)F-FLT PET before and after radiation with outcome (12 month PFS) * To compare the performance of (18)F-FLT-PET to that of MR perfusion, proton magnetic resonance spectroscopy (1H-MRSI) and (18)F-FDG PET in prediction of tumor response, time to progression and overall survival time. ELIGIBILITY: * Children less than 18 years of age with malignant gliomas for whom radiation therapy is prescribed. * Adequate organ function defined as: * Hepatic: SGOT, SGPT less than 5 times the ULN; total and direct bilirubin less than or equal to 2 times the ULN * Renal: Serum creatinine must be within the upper limit of normal values * Fasting serum glucose less than 150 mg/dL * Negative serum or urine pregnancy test in females of childbearing potential DESIGN: -Patients will undergo MRI (with 1H-MRSI and perfusion), (18)F-FLT PET and (18)F-FDG PET within 2 weeks of each other at the following time points: pre-radiation therapy, 1-3 weeks post-radiation therapy, and at the time of suspected progression.