Brain Tumors: An Update on Clinical PET Research in Gliomas.

A previous review published in 2012 demonstrated the role of clinical PET for diagnosis and management of brain tumors using mainly FDG, amino acid tracers, and 18F-fluorothymidine. This review provides an update on clinical PET studies, most of which are motivated by prediction of prognosis and planning and monitoring of therapy in gliomas. For FDG, there has been additional evidence supporting late scanning, and combination with 13N ammonia has yielded some promising results. Large neutral amino acid tracers have found widespread applications mostly based on 18F-labeled compounds fluoroethyltyrosine and fluorodopa for targeting biopsies, therapy planning and monitoring, and as outcome markers in clinical trials. 11C-alpha-methyltryptophan (AMT) has been proposed as an alternative to 11C-methionine, and there may also be a role for cyclic amino acid tracers. 18F-fluorothymidine has shown strengths for tumor grading and as an outcome marker. Studies using 18F-fluorocholine (FCH) and 68Ga-labeled compounds are promising but have not yet clearly defined their role. Studies on radiotherapy planning have explored the use of large neutral amino acid tracers to improve the delineation of tumor volume for irradiation and the use of hypoxia markers, in particular 18F-fluoromisonidazole. Many studies employed the combination of PET with advanced multimodal MR imaging methods, mostly demonstrating complementarity and some potential benefits of hybrid PET/MR.