DOI: 10.1007/s00259-018-4166-1Pages: 1-11

Comparison of 18F-GE-180 and dynamic 18F-FET PET in high grade glioma: a double-tracer pilot study

1. University Hospital, LMU Munich, Department of Nuclear Medicine

2. German Cancer Consortium (DKTK), Partner Site Munich; and German Cancer Research Center (DKFZ)

3. University Hospital, LMU Munich, Department of Radiation Oncology

4. University Hospital, LMU Munich, Institute of Clinical Radiology

5. University Hospital, LMU Munich, Department of Neuropathology

6. University of Regensburg, Department of Psychiatry and Psychotherapy

7. University Hospital, LMU Munich, Department of Neurosurgery

Correspondence to:
Nathalie L. Albert
Tel: +49 89 4400 52431
Email: nathalie.albert@med.uni-muenchen.de

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Abstract

Background

PET represents a valuable tool for glioma imaging. In addition to amino acid tracers such as 18F-FET, PET targeting the 18-kDa mitochondrial translocator-protein (TSPO) is of high interest for high-grade glioma (HGG) imaging due to its upregulation in HGG cells. 18F-GE-180, a novel TSPO ligand, has shown a high target-to-background contrast in HGG. Therefore, we intra-individually compared its uptake characteristics to dynamic 18F-FET PET and contrast-enhanced MRI in patients with HGG.

Methods

Twenty HGG patients (nine IDH-wildtype, 11 IDH-mutant) at initial diagnosis (n = 8) or recurrence (n = 12) were consecutively included and underwent 18F-GE-180 PET, dynamic 18F-FET PET, and MRI. The maximal tumour-to-background ratios (TBRmax) and biological tumour volumes (BTV) were evaluated in 18F-GE-180 and 18F-FET PET. Dynamic 18F-FET PET analysis included the evaluation of minimal time-to-peak (TTPmin). In MRI, the volume of contrast-enhancement was delineated (VOLCE). Volumes were spatially correlated using the Sørensen–Dice coefficient.

Results

The median TBRmax tended to be higher in 18F-GE-180 PET compared to 18F-FET PET [4.58 (2.33–8.95) vs 3.89 (1.56–7.15); p = 0.062] in the overall group. In subgroup analyses, IDH-wildtype gliomas showed a significantly higher median TBRmax in 18F-GE-180 PET compared to 18F-FET PET [5.45 (2.56–8.95) vs 4.06 (1.56–4.48); p = 0.008]; by contrast, no significant difference was observed in IDH-mutant gliomas [3.97 (2.33–6.81) vs 3.79 (2.01–7.15) p = 1.000]. Only 5/20 cases showed higher TBRmax in 18F-FET PET compared to 18F-GE-180 PET, all of them being IDH-mutant gliomas. No parameter in 18F-GE-180 PET correlated with TTPmin (p > 0.05 each). There was a tendency towards higher median BTVGE-180 [32.1 (0.4–236.0) ml] compared to BTVFET [19.3 (0.7–150.2) ml; p = 0.062] with a moderate spatial overlap [median Sørensen–Dice coefficient 0.55 (0.07–0.85)]. In MRI, median VOLCE [9.7 (0.1–72.5) ml] was significantly smaller than both BTVFET and BTVGE180 (p < 0.001 each), leading to a poor spatial correlation with BTVGE-180 [0.29 (0.01–0.48)] and BTVFET [0.38 (0.01–0.68)].

Conclusion

PET with 18F-GE-180 and 18F-FET provides differing imaging information in HGG dependent on the IDH-mutational status, with diverging spatial overlap and vast exceedance of contrast-enhancement in MRI. Combined PET imaging might reveal new insights regarding non-invasive characterization of tumour heterogeneity and might influence patients’ management.

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  • Accepted: Sep 11, 2018
  • Online: Sep 22, 2018

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