Static and dynamic ¹⁸F-FET PET for the characterization of gliomas defined by IDH and 1p/19q status

The molecular features isocitrate dehydrogenase (IDH) mutation and 1p/19q co-deletion have gained major importance for both glioma typing and prognosis and have, therefore, been integrated in the World Health Organization (WHO) classification in 2016. The aim of this study was to characterize static and dynamic O-(2-¹⁸F-fluoroethyl)-L-tyrosine (¹⁸F-FET) PET parameters in gliomas with or without IDH mutation or 1p/19q co-deletion.

Ninety patients with newly diagnosed and untreated gliomas with a static and dynamic ¹⁸F-FET PET scan prior to evaluation of tumor tissue according to the 2016 WHO classification were identified retrospectively. Mean and maximum tumor-to-brain ratios (TBR_mean/max), as well as dynamic parameters (time-to-peak and slope) of ¹⁸F-FET uptake were calculated.

Sixteen (18%) oligodendrogliomas (IDH mutated, 1p/19q co-deleted), 27 (30%) astrocytomas (IDH mutated only), and 47 (52%) glioblastomas (IDH wild type only) were identified. TBR_mean, TBR_max, TTP and slope discriminated between IDH mutated astrocytomas and IDH wild type glioblastomas (P < 0.01). TBR_mean showed the best diagnostic performance (cut-off 1.95; sensitivity, 89%; specificity, 67%; accuracy, 81%). None of the parameters discriminated between oligodendrogliomas (IDH mutated, 1p/19q co-deleted) and glioblastomas or astrocytomas. Furthermore, TBR_mean, TBR_max, TTP, and slope discriminated between gliomas with and without IDH mutation (p < 0.01). The best diagnostic performance was obtained for the combination of TTP with TBR_max or slope (accuracy, 73%).

Data suggest that static and dynamic ¹⁸F-FET PET parameters may allow determining non-invasively the IDH mutation status. However, IDH mutated and 1p/19q co-deleted oligodendrogliomas cannot be differentiated from glioblastomas and astrocytomas by ¹⁸F-FET PET.