Correlation of early PET findings with tumor response to molecular targeted agents in patients with advanced driver-mutated non-small cell lung cancer.

Recent advances in positron emission tomography with fluorine-18-fluorodeoxyglucose (FDG-PET) have facilitated not only the diagnosis and staging of lung cancer, but also the prediction of treatment outcome. The present study was designed to assess the usefulness of early FDG-PET examination for predicting subsequent tumor size reduction in response to molecular targeted agents in metastatic non-small cell lung cancer (NSCLC) with sensitive gene anomalies. I. In 29 targeted lesions of 10 NSCLC patients, changes in FDG uptake before and on day 7 after the initiation of molecular targeted therapy (gefitinib, n = 7; crizotinib, n = 3) were compared with subsequent radiographic tumor size reduction by RECIST. FDG uptake was evaluated as the maximum standardized uptake value (SUVmax) of each targeted lesion. SUVmax decreased in all lesions after therapy (mean SUVmax 8.3 ± 3.4 before to 3.7 ± 1.8 after therapy, p < 0.05). The % decrease in SUVmax of each lesion was significantly correlated with the % tumor size reduction (r = 0.44). In addition, the reduction rate of SUVmax in metastatic bone lesions after initiation of molecular targeted therapy was significantly lower than that in targeted organs (27.1 ± 27.5 vs. 51.2 ± 21.3%, respectively, p < 0.05). Early reduction in FDG-PET uptake after initiation of molecular targeted agents was able to predict subsequent tumor reduction in patients harboring EGFR-mutated or ALK-positive NSCLC. In addition, nontargeted bone metastasis may have different glucose metabolism after TKI treatment compared with other involved organs.