Impact of <sup>18</sup>F-FET PET/MRI on Clinical Management of Brain Tumor Patients
Cornelia Brendle, Caroline Maier, Benjamin Bender, Jens Schittenhelm, Frank Paulsen, Mirjam Renovanz, Constantin Roder, Salvador Castaneda Vega, Ghazaleh Tabatabai, Ulrike Ernemann, Christian la Fougère
Abstract
Multiparametric PET-MRI with the amino-acid analog <sup>18</sup>F-FET enables the simultaneous assessment of molecular, morphologic, and functional brain tumor characteristics. Although it is considered the most accurate non-invasive approach in brain tumors, its relevance for patient management is still under debate. Here we report the diagnostic performance of <sup>18</sup>F-FET PET/MR and its impact on clinical management in a retrospective patient cohort. <b>Methods:</b> We retrospectively analyzed brain tumor patients who underwent <sup>18</sup>F-FET PET/MR between 2017 and 2018. <sup>18</sup>F-FET PET/MR examinations were indicated clinically due to equivocal standard imaging or clinical course. Histological confirmation or clinical and standard imaging follow-up served as the reference standard. We evaluated <sup>18</sup>F-FET PET/MR accuracy in identifying malignancy in untreated suspect lesions (category new diagnosis) and true progression during adjuvant treatment (category detection of progression) in a clinical setting. Using multiple regression, we also estimated the contribution of single modalities to produce an optimal PET/MRI outcome. We assessed the recommended and applied therapies before and after <sup>18</sup>F-FET PET/MR and noted if the treatment changed based on the <sup>18</sup>F-FET PET/MR outcome. <b>Results:</b> We included 189 cases in the study. <sup>18</sup>F-FET PET/MR allowed the identification of malignancy at new diagnosis with an accuracy of 85% and identified true progression with an accuracy of 93%. Contrast enhancement, <sup>18</sup>F-FET PET uptake, and tracer kinetics were the major contributors to an optimal PET/MR outcome. In the previously equivocal patients, <sup>18</sup>F-FET PET/MR changed the clinical management in 33% of the untreated lesions and 53% of the tumor progressions. <b>Conclusion:</b> Our results suggest that <sup>18</sup>F-FET PET/MR helps clarify equivocal conditions and profoundly supports brain tumor patients9 clinical management. The optimal modality setting of <sup>18</sup>F-FET PET/MR and the clinical value of a simultaneous examination need further exploration. At a new diagnosis, multiparametric <sup>18</sup>F-FET PET/MR might help prevent unnecessary invasive procedures by ruling out malignancy; however, adding static <sup>18</sup>F-FET PET to an already existing MR examination seems to be of equal value. At detection of progression, multiparametric <sup>18</sup>F-FET PET/MR may increase therapy effectiveness by distinguishing between tumor progression and therapy-related imaging alterations.