Abstract BACKGROUND O-(2-18Ffluoroethyl)-L-tyrosine (¹⁸FFET) PET is predominantly applied for molecular imaging of diffuse gliomas. In contrast, data on the clinical utility of ¹⁸FFET PET in circumscribed astrocytic gliomas (CAG) remain scarce. MATERIAL AND METHODS We retrospectively identified adult CAG patients who underwent ¹⁸FFET PET imaging (i) before diagnosis, (ii) at suspected relapse, or (iii) for response assessment at three institutions. Maximum and mean tumor-to-brain ratios (TBRmax, TBRmean) and metabolic tumor volumes were assessed according to the PET RANO 1.0 criteria. Diagnostic performance in differentiating treatment-related changes from tumor relapse was evaluated using ROC analysis and Fisher’s exact test. RESULTS We evaluated 79 ¹⁸FFET PET scans of 42 patients, including nine (21%) with actionable molecular targets. 65% of CAG WHO grade 1 and 100% of CAG WHO grades 2 or 3 had measurable ¹⁸FFET uptake according to the PET RANO 1.0 criteria. In these patients, TBR values of CAG WHO grades 2 or 3 were significantly higher than in pilocytic astrocytomas (P0.01). There was no significant difference in TBR between CAG with or without actionable targets (P0.05). Following various treatments, response assessment according to the PET RANO 1.0 criteria differed from changes in MRI in 5 of 11 patients (45%). Treatment-related changes were confirmed neuropathologically or clinicoradiologically in 12 patients (43%). In CAG WHO grades 2 or 3, the accuracy of ¹⁸FFET PET to identify treatment-related changes was 82% using single PET scans and 100% using serial PET imaging (P0.05). CONCLUSION ¹⁸FFET PET can add valuable information for the clinical management of patients with CAG.
Werner et al. (Wed,) studied this question.