¹⁸F-FET PET Imaging in Differentiating Glioma Progression from Treatment-Related Changes: A Single-Center Experience.

Abstract

In glioma patients, differentiation between tumor progression (TP) and treatment-related changes (TRCs) remains challenging. Difficulties in classifying imaging alterations may result in a delay or an unnecessary discontinuation of treatment. PET using <i>O</i>-(2-¹⁸F-fluoroethyl)-l-tyrosine (¹⁸F-FET) has been shown to be a useful tool for detecting TP and TRCs. <b>Methods:</b> We retrospectively evaluated 127 consecutive patients with World Health Organization grade II-IV glioma who underwent ¹⁸F-FET PET imaging to distinguish between TP and TRCs. ¹⁸F-FET PET findings were verified by neuropathology (40 patients) or clinicoradiologic follow-up (87 patients). Maximum tumor-to-brain ratios (TBR_max) of ¹⁸F-FET uptake and the slope of the time-activity curves (20-50 min after injection) were determined. The diagnostic accuracy of ¹⁸F-FET PET parameters was evaluated by receiver-operating-characteristic analysis and χ² testing. The prognostic value of ¹⁸F-FET PET was estimated using the Kaplan-Meier method. <b>Results:</b> TP was diagnosed in 94 patients (74%) and TRCs in 33 (26%). For differentiating TP from TRCs, receiver-operating-characteristic analysis yielded an optimal ¹⁸F-FET TBR_max cutoff of 1.95 (sensitivity, 70%; specificity, 71%; accuracy, 70%; area under the curve, 0.75 ± 0.05). The highest accuracy was achieved by a combination of TBR_max and slope (sensitivity, 86%; specificity, 67%; accuracy, 81%). However, accuracy was poorer when tumors harbored isocitrate dehydrogenase (<i>IDH</i>) mutations (91% in <i>IDH</i>-wild-type tumors, 67% in <i>IDH</i>-mutant tumors, <i>P</i> < 0.001). ¹⁸F-FET PET results correlated with overall survival (<i>P</i> < 0.001). <b>Conclusion:</b> In our neurooncology department, the diagnostic performance of ¹⁸F-FET PET was convincing but slightly inferior to that of previous reports.