Dynamic 18F-FET PET in Newly Diagnosed Astrocytic Low-Grade Glioma Identifies High-Risk Patients

Because the clinical course of low-grade gliomas in the individual adult patient varies considerably and is unpredictable, we investigated the prognostic value of dynamic F-18-fluorethyltyrosine (F-18-FET) PET in the early diagnosis of astrocytic low-grade glioma (World Health Organization grade II). Methods: Fifty-nine patients with newly diagnosed low-grade glioma and dynamic P-18-FET PET before histopathologic assessment were retrospectively investigated. F-18-FET PET analysis comprised a qualitative visual classification of lesions; assessment of the semiquantitative parameters maximal, mean, and total standardized uptake value as ratio to background and biologic tumor volume; and dynamic analysis of intratumoral F-18-FET uptake over time (increasing vs. decreasing time-activity curves). The correlation between PET parameters and progression-free survival, overall survival, and time to malignant transformation was investigated. Results: F-18-FET uptake greater than the background level was found in 34 of 59 tumors. Dynamic F-18-FET uptake analysis was available for 30 of these 34 patients. Increasing and decreasing time-activity curves were found in 18 and 12 patients, respectively. Neither the qualitative factor presence or absence of F-18-FET uptake nor any of the semiquantitative uptake parameters significantly influenced clinical outcome. In contrast, decreasing time-activity curves in the kinetic analysis were highly prognostic for shorter progression-free survival and time to malignant transformation (P < 0.001). Conclusion: Absence of F-18-FET uptake in newly diagnosed astrocytic low-grade glioma does not generally indicate an indolent disease course. Among the F-18-FET-positive gliomas, decreasing time-activity curves in dynamic F-18-FET PET constitute an unfavorable prognostic factor in astrocytic low-grade glioma and, by identifying high-risk patients, may ease treatment decisions.