MTOR and central nervous system cancer: The widely used oncologic and neurologic radiotracer, 18F-FDG, has been employed not only for evaluating the efficacy of bevacizumab [the only U.S. Food and Drug Administration (FDA)–approved targeted inhibitor for recurrent GBM (20)] for newly diagnosed and recurrent GBM (9, 10), but also for monitoring efficacy of novel inhibitors against molecular targets of interest in glioma, such as c-Met [a receptor tyrosine kinase (RTK) whose ligand is hepatocyte growth factor] (16), phosphoinositide 3 (PI3)-kinase (21), mammalian target of rapamycin (mTOR) (22), and other RTKs (17).