Quantitative PET-CT in Evaluating Response after Radiotherapy

It is evident in the literature that F-18 fluorodeoxyglucose positron emission tomography enables us to evaluate tumor response to chemo-, radiotherapy or combined. Cellularity, proliferate rate and tumor size play essential roles in FDG uptake. Both pre- and post-treatment FDG PET-CT are useful in predicting response of treatment and status of residual tumor. Such an assessment is frequently achievable by the visual inspection. However, quantitative analysis of tumor FDG uptake is generally needed to precisely compare and predict tumor response in the earlier time. The commonly quantitative measurement used by PET is the standard uptake value (SUV) that reflects relative changes of tumor glucose use during treatment. Besides SUV, incorporation of glucose sensitivity into consideration may be potentially useful as a supplementary global index to reflect the true treatment response especially if patients are scanned with different serum glucose levels.