Fluoroethyltyrosine for Evaluation of Intracranial Neoplasms

PRIMARY OBJECTIVES: I. To determine if FET PET can differentiate between benign treatment-related changes (TRC) and recurrent glioma in comparison to a composite standard of truth (CSOT) that includes pathology and other clinical information, evaluated using estimates of sensitivity and specificity (Combined populations) SECONDARY OBJECTIVES: I. To determine if FET PET can differentiate between benign TRC and recurrent glioma in comparison to a histopathological standard of truth.(Combined populations). II. To determine if FET PET can differentiate between benign TRC and recurrent glioma in comparison to a CSOT evaluated using estimates other than subject-based sensitivity and specificity.(Combined populations). III. To assess the safety of FET PET, as determined by treatment emergent adverse events (TEAEs) within 48 hours of FET administration.(Combined populations). IV. To describe the inter-reader variability between 3 independent blinded readers of FET PET images in assessments of benign TRC versus recurrent glioma.(Combined populations). V. To describe intra-reader variability between 3 independent blinded readers of FET PET images in the assessments of benign TRC versus recurrent glioma.(Combined populations). EXPLORATORY OBJECTIVES: I. To assess relationships between serial FET PET and clinical outcome (benign TRC and recurrence) in patients with recurrent metastatic lesions, recurrent high grade gliomas and recurrent low-grade gliomas. II. To determine if MRI can differentiate between benign treatment-related changes and recurrence. III. To describe the distribution of the standardized uptake value (SUV) and tumor-to-background ratio (TBR) for observed lesions. IV. To determine if FET PET can differentiate between benign TRC and recurrent metastatic lesions. V. To determine if FET PET can accurately differentiate between low-grade and high-grade gliomas (Population 2). OUTLINE: Participants receive F-18 fluoroethyltyrosine intravenously (IV) over approximately 1 minute and undergo PET over 40 minutes. After completion of study treatment, participants are followed up periodically.