PT - JOURNAL ARTICLE AU - Cornelia Brendle AU - Caroline Maier AU - Benjamin Bender AU - Jens Schittenhelm AU - Frank Paulsen AU - Mirjam Renovanz AU - Constantin Roder AU - Salvador Castaneda-Vega AU - Ghazaleh Tabatabai AU - Ulrike Ernemann AU - Christian la Fougère TI - Impact of <sup>18</sup>F-FET PET/MR on clinical management of brain tumor patients AID - 10.2967/jnumed.121.262051 DP - 2021 Aug 01 TA - Journal of Nuclear Medicine PG - jnumed.121.262051 4099 - http://jnm.snmjournals.org/content/early/2021/08/05/jnumed.121.262051.short 4100 - http://jnm.snmjournals.org/content/early/2021/08/05/jnumed.121.262051.full AB - Multiparametric PET-MRI with the amino-acid analog 18F-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 18F-FET PET/MR and its impact on clinical management in a retrospective patient cohort. Methods: We retrospectively analyzed brain tumor patients who underwent 18F-FET PET/MR between 2017 and 2018. 18F-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 18F-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 18F-FET PET/MR and noted if the treatment changed based on the 18F-FET PET/MR outcome. Results: We included 189 cases in the study. 18F-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, 18F-FET PET uptake, and tracer kinetics were the major contributors to an optimal PET/MR outcome. In the previously equivocal patients, 18F-FET PET/MR changed the clinical management in 33% of the untreated lesions and 53% of the tumor progressions. Conclusion: Our results suggest that 18F-FET PET/MR helps clarify equivocal conditions and profoundly supports brain tumor patients' clinical management. The optimal modality setting of 18F-FET PET/MR and the clinical value of a simultaneous examination need further exploration. At a new diagnosis, multiparametric 18F-FET PET/MR might help prevent unnecessary invasive procedures by ruling out malignancy; however, adding static 18F-FET PET to an already existing MR examination seems to be of equal value. At detection of progression, multiparametric 18F-FET PET/MR may increase therapy effectiveness by distinguishing between tumor progression and therapy-related imaging alterations.