18F-FDG PET/CT in therapy response and in predicting responders or non-responders in malignant pleural mesothelioma patients, by using semi-quantitative mRECIST and EORTC criteria

Objective: To evaluate the role of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in therapy response assessment according modified response evaluating criteria of solid tumors (mRECIST) and the predictive role of volume-based semi-quantitative parameters in patients with malignant pleural mesothelioma (MPM). Furthermore modified RECIST criteria for MPM mRECIST and the European Organization for Research and Treatment of Cancer (EORTC) criteria were compared and the predictive role of18F-FDG PET/CT in the post-therapy outcome. Subjects and Methods: Thirty five selected patients with MPM underwent18F-FDG PET/CT scan at baseline (1) and after therapy (2). Semi-quantitative18F-FDG PET/CT parameters were collected for each scan and also differences (δ) δSUVmax, δSUVav, δMTV, δTLG, response index (RI)max% and RIav% were evaluated. Radiologic response to therapy was assessed by using the mRECIST and EORTC. Results: The correlation between response to therapy assessed by EORTC and mRECIST criteria was moderate (K=0.418; 95%CI:0099-0736). According to mRECIST, statistical differences between responders and non-responders were significant in the analysis of semi-quantitative parameters. According mRECIST criteria, all parameters defined a good area under the curve (AUC) but the better AUC resulted for δMTV (cut-off ≤ 11.3, sensitivity=91.3%, specificity=91.7%) and δTLG (cut-off≤59.1, sensitivity=82.6%, specificity=100%). Kaplan-Meier curves between responders and non-responders did not show statistically significant differences. Conclusion: The semi-quantitative analysis of18F-FDG PET/CT has an important role in MPM therapy response assessment and has a predictive role in distinguishing responders and non-responders.