Prognostic and predictive role of [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with unresectable malignant pleural mesothelioma (MPM) treated with up-front pemetrexed-based chemotherapy

The aim of this study was to evaluate the role of metabolic parameters analyzed at baseline and at interim FDG-PET in predicting disease outcome in unresectable MPM patients receiving pemetrexed-based chemotherapy. A consecutive series of MPM patients treated between February 2004 and July 2013 with first-line pemetrexed-based chemotherapy, and evaluated by FDG-PET and CT scan at baseline and after two cycles of chemotherapy, was reviewed. Best CT scan response was assessed according to modified RECIST criteria. Progression-free survival (PFS) and overall survival (OS) were correlated with FDG-PET parameters, such as maximum standardized uptake value (SUVmax), total lesion glycolysis (TLG), and percentage changes in SUVmax (Delta SUV) and TLG (Delta TLG). Overall, 142 patients were enrolled; 77 (54%) received talc pleurodesis before chemotherapy. Baseline SUVmax and TLG showed a statistically significant correlation with PFS and OS (P < 0.05) in both group of patients (treated and untreated with pleurodesis). In 65 patients not receiving pleurodesis, SUVmax reduction >= 25% (Delta SUV >= 25%) and TLG reduction >= 30% (Delta TLG >= 30%) were significantly associated with longer PFS (P < 0.05). Patients showing both Delta SUV >= 25% and Delta TLG >= 30% responses had a significant reduction in the risk of disease progression (HR: 0.31, P < 0.001) and death (HR: 0.52, P = 0.044). Neither Delta SUV nor Delta TLG showed similar association with survival outcomes in patients treated with pleurodesis. Our study confirmed the prognostic role of baseline FDG-PET in a large series of MPM patients treated with first-line pemetrexed-based chemotherapy. Moreover, use of Delta SUV >= 25% and Delta TLG >= 30% as cut-off values to define early metabolic response supported the role of FDG-PET in predicting disease outcome and treatment response in patients not receiving pleurodesis.