Evaluation of metabolic response with 18F-FDG PET-CT in patients with advanced or recurrent thymic epithelial tumors

摘要

Background Patients with advanced or recurrent thymic epithelial tumors (TETs) often need several consecutive lines of chemotherapy. The aim of this retrospective monocentric study was to test whether 18F-Fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) is able to monitor standard chemotherapy efficacy in those patients and whether metabolic response correlates with morphovolumetric response as assessed by Response Evaluation Criteria in Solid Tumor (RECIST). Methods We evaluated 27 consecutive patients with advanced (16 patients) or recurrent (11 patients) TETs. All patients underwent 18F-FDG PET-CT before and after at least 3?cycles of chemotherapy. Maximum standardized uptake value (SUV_max) of all detected lesions was recorded and the most 18F-FDG avid lesion in each patient was selected for determination of percentage change of SUV_max (ΔSUV_max) in pre- and post-treatment scans. Tumor response was assessed by contrast-enhanced computed tomography (CE-CT) using RECIST criteria. Receiver operating characteristic (ROC) curve analysis was performed to define the optimal threshold of ΔSUV_max discriminating responders from non-responders. Results Metabolic response expressed as ΔSUV_max was significantly correlated with morphovolumetric response (Spearman’s rank correlation, r =?0.64, p =?0.001). ROC curve analysis showed that a ΔSUV_max value of -25% could discriminate responders from non-responders with a sensitivity of 88% and a specificity of 80%. Conversely, basal SUV_max values were not predictive of morphovolumetric tumor response. Conclusions Our findings indicate that metabolic response assessed by 18F-FDG PET-CT, through evaluation of ΔSUV_max, may allow identification of responders and non-responders thus guiding adaptation of therapy in patients with advanced or recurrent TETs.