Clinical potential of 18FFET PET in patients with circumscribed astrocytic glioma

PurposeTo investigate the clinical potential of O-(2-18Ffluoroethyl)-L-tyrosine (18FFET) PET imaging in the management of circumscribed astrocytic gliomas (CAG), a rare glioma subtype with limited imaging data.MethodsWe 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.ResultsWe evaluated 79 18FFET PET scans of 42 patients, including nine (21%) with actionable molecular targets. Measurable 18FFET uptake was observed in 65% of WHO grade 1 and 100% of WHO grade 2 and 3 CAG. TBR values were significantly higher in WHO grade 2 and 3 CAG than in pilocytic astrocytomas (P 0.05). In 5 of 11 patients (45%), treatment response assessment by PET RANO 1.0 differed from MRI. Treatment-related changes were confirmed 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 (P < 0.05).Conclusions18FFET PET can contribute to clinical management of patients with CAG by detecting measurable disease, differentiating treatment-related changes from tumor progression, and showing potential in treatment response assessment through longitudinal imaging.