The use of dynamic O-(2-18F-fluoroethyl)-l-tyrosine PET in the diagnosis of patients with progressive and recurrent glioma

Abstract

Background: We evaluated the diagnostic value of static and dynamic O-(2-[(18)F]fluoroethyl)-L-tyrosine ((18)F-FET) PET parameters in patients with progressive or recurrent glioma.

Methods: We retrospectively analyzed 132 dynamic (18)F-FET PET and conventional MRI scans of 124 glioma patients (primary World Health Organization grade II, n = 55; grade III, n = 19; grade IV, n = 50; mean age, 52 ± 14 y). Patients had been referred for PET assessment with clinical signs and/or MRI findings suggestive of tumor progression or recurrence based on Response Assessment in Neuro-Oncology criteria. Maximum and mean tumor/brain ratios of (18)F-FET uptake were determined (20-40 min post-injection) as well as tracer uptake kinetics (ie, time to peak and patterns of the time-activity curves). Diagnoses were confirmed histologically (95%) or by clinical follow-up (5%). Diagnostic accuracies of PET and MR parameters for the detection of tumor progression or recurrence were evaluated by receiver operating characteristic analyses/chi-square test.

Results: Tumor progression or recurrence could be diagnosed in 121 of 132 cases (92%). MRI and (18)F-FET PET findings were concordant in 84% and discordant in 16%. Compared with the diagnostic accuracy of conventional MRI to diagnose tumor progression or recurrence (85%), a higher accuracy (93%) was achieved by (18)F-FET PET when a mean tumor/brain ratio ≥2.0 or time to peak <45 min was present (sensitivity, 93%; specificity, 100%; accuracy, 93%; positive predictive value, 100%; P < .001).

Conclusion: Static and dynamic (18)F-FET PET parameters differentiate progressive or recurrent glioma from treatment-related nonneoplastic changes with higher accuracy than conventional MRI.

Keywords: FET PET; malignant glioma; progressive disease; tumor recurrence.

© The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Figures

Fig. 1.

A 70-year-old patient with an anaplastic astrocytoma (WHO grade III). (Top row, left) Contrast-enhanced MRI 31 months after radiation therapy suggests tumor progression. (Top row, middle) In contrast, 18F-FET shows only slight metabolic activity (TBRmax, 1.4), and (top row, right) the time–activity curve shows a constantly increasing 18F-FET uptake, consistent with treatment-related changes. (Bottom row, right) After a stereotactic-guided biopsy, histological examination yielded signs of radiation-induced necrosis (hematoxylin and eosin [H&E] staining, original magnification ×200; scale bar, 50 µm). (Bottom row, left) Brain parenchyma shows reactive changes and blood vessels with thickened hyalinized walls (arrows; H&E staining, original magnification ×100; scale bar, 1.000 µm).

Fig. 2.

A 35-year-old patient with initial diagnosis of a diffuse astrocytoma (WHO grade II). Follow-up MRI 86 months after initial diagnosis shows a slight progression of the hyperintensity in the T2-weighted MRI, but no clear contrast enhancement in the right temporal. In contrast, 18F-FET shows highly increased metabolic activity (TBRmax, 3.9) in the right temporal, and the time–activity curve shows an early 18F-FET uptake (<20 min) followed by a descent (pattern III), consistent with tumor recurrence. After a stereotactic-guided biopsy of the metabolically active tumor, histological examination was consistent with a malignant progression to an anaplastic oligoastrocytoma (WHO grade III).