Barrio JR, Huang SC, Satyamurthy N, et al. - The present study was conducted to not deny the clinical value of 2-FDG PET; it is a reminder that when one extends the use of an appropriately qualified imaging method, new observations may arise and further validation would be necessary. In health and disease states, applying both 2-FDG and Me-4FDG should provide a more complete picture of glucose utilization via both glucose transporters and sodium-dependent glucose cotransporter transporters. It is relevant to appreciate the potential limitations of 2-FDG as a surrogate for glucose metabolic rate and the potential reasons for variability in LC, given the widespread use of 2-FDG PET to infer glucose metabolism. The results reveal that variability in LC is important, especially whether it changes over the course of disease progression (e.g., an evolving tumor) even when the readout for the 2-FDG PET study is only an SUV parameter.