TY - JOUR T1 - Clinical utility of different approaches for detection of late pseudoprogression in glioblastoma with O-(2-[<sup>18</sup>F]fluoroethyl)-L-tyrosine PET JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 493 LP - 493 VL - 60 IS - supplement 1 AU - Olivia Kertels AU - Milena Mihovilovic AU - Thomas Linsenmann AU - Almuth Kessler AU - Johannes Tran-Gia AU - Malte Kircher AU - Joachim Brumberg AU - Camelia Monoranu AU - Samuel Samnick AU - Ralf-Ingo Ernestus AU - Mario Löhr AU - Philipp Meyer AU - Constantin Lapa Y1 - 2019/05/01 UR - http://jnm.snmjournals.org/content/60/supplement_1/493.abstract N2 - 493Purpose: Positron emission tomography/computed tomography (PET/CT) using O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) has proven valuable in differentiating tumor recurrence and progression from therapy-induced changes. This study aimed to investigate the diagnostic performance of several analytic approaches in the setting of suspected late pseudoprogression (PsP) in glioblastoma (GBM). Methods: Retrospective analysis of tumor recurrence was performed in 36 patients with histopathologically confirmed GBM and suspicion of recurrence/disease progression &gt;12 weeks from cessation of irradiationas based on magnetic resonance imaging and Response Assessment in Neuro-Oncology (RANO) working group criteria. Images were analyzed semi-quantitatively employing tumor-to-brain (TBR) ratios using 10 different analytic approaches (i.e., relying on 7 and 3 different methods for tumor and normal brain reference region definition, respectively). Histopathology and/or clinical and imaging follow-up served as reference. Results: [18F]FET-PET was able to reliably differentiate PsP from true tumor progression with areas under the receiver operating characteristic curve ranging from 0.80 to 0.88 (all p &lt; 0.01). Irrespective of the approach chosen, the classification differences between the applied methods were not significant (all p &gt; 0.05), albeit approaches focusing on voxels with highest uptake tended to perform superior. Conclusions: Irrespective of the analytical approach, [18F]FET-PET is a robust tool for detection of late PsP with only minor differences between different analytical approaches. However, methodological standardization and harmonization are needed to ensure comparability between different centers. ER -