Early Pharmacodynamic Assessment Using 18F-Fluorodeoxyglucose Positron-Emission Tomography on Molecular Targeted Therapy and Cytotoxic Chemotherapy for Clinical Outcome Prediction

Early prediction of therapeutic outcome is important in determining whether the ongoing therapy is beneficial. In addition to anatomical response determined using the Response Evaluation Criteria in Solid Tumors (RECIST) criteria, recent studies have indicated that change in tumor glucose use on or after treatment correlates with histopathologic tumor regression and patient outcomes. This Perspective discusses the use of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) for pharmacodynamic evaluation in a very early phase of treatment to predict clinical outcomes in patients with advanced non–small-cell lung cancer. We conducted a study to assess whether early metabolic response determined using FDG-PET correlated with clinical outcomes in patients treated with gefitinib or those treated with carboplatin plus paclitaxel (CP). Early metabolic response to gefitinib, but not CP, correlated with the late metabolic response, anatomical response, progression-free survival, and even overall survival. A rapid effect of molecular targeted agents might not be aptly evaluated using the conventional criteria, eg, RECIST, in a very early phase of treatment before volumetric shrinkage of the tumor. Based on the findings of several studies, and on the findings from our study, use of FDG-PET might enable prediction of clinical outcomes at a very early stage of treatment, especially in patients treated with molecular targeted agents with rapid clinical efficacy.