DOI: 10.1007/s00259-017-3799-9Pages: 1-9

TSPO PET for glioma imaging using the novel ligand 18F-GE-180: first results in patients with glioblastoma

1. LMU Munich, Department of Nuclear Medicine

2. German Cancer Consortium (DKTK), partner site Munich; and German Cancer Research Center (DKFZ)

3. “Munich Cluster of Systems Neurology (SyNergy)”

4. LMU Munich, Department of Radiation Oncology

5. University of Regensburg, Department of Psychiatry and Psychotherapy

6. LMU Munich, Department of Neurosurgery

Correspondence to:
Nathalie L. Albert
Tel: +4989440052431
Email: Nathalie.Albert@med.uni-muenchen.de

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Abstract

Objective

The 18-kDa mitochondrial translocator protein (TSPO) was reported to be upregulated in gliomas. 18F-GE-180 is a novel 3rd generation TSPO receptor ligand with improved target-to-background contrast compared to previous tracers. In this pilot study, we compared PET imaging with 18F-GE-180 and MRI of patients with untreated and recurrent pretreated glioblastoma.

Methods

Eleven patients with histologically confirmed IDH wildtype gliomas (10 glioblastomas, 1 anaplastic astrocytoma) underwent 18F-GE-180 PET at initial diagnosis or recurrence. The PET parameters mean background uptake (SUVBG), maximal tumour-to-background ratio (TBRmax) and PET volume using different thresholds (SUVBG × 1.6, 1.8 and 2.0) were evaluated in the 60-80 min p.i. summation images. The different PET volumes were compared to the contrast-enhancing tumour volume on MRI.

Results

All gliomas were positive on 18F-GE-180 PET and were depicted with extraordinarily high tumour-to-background contrast (median SUVBG 0.47 (0.37-0.93), TBRmax 6.61 (3.88-9.07)). 18F-GE-180 uptake could be found even in areas without contrast enhancement on MRI, leading to significantly larger PET volumes than MRI-based volumes (median 90.5, 74.5, and 63.8 mL vs. 31.0 mL; p = 0.003, 0.004, 0.013). In percentage difference, the PET volumes were on average 179%, 135%, and 90% larger than the respective MRI volumes. The median spatial volumetric correlation (Sørensen-Dice coefficient) of PET volumes and MRI volumes prior to radiotherapy was 0.48, 0.54, and 0.58.

Conclusion

18F-GE-180 PET provides a remarkably high tumour-to-background contrast in untreated and pretreated glioblastoma and shows tracer uptake even beyond contrast enhancement on MRI. To what extent 18F-GE-180 uptake reflects the tumour extent of human gliomas and inflammatory cells remains to be evaluated in future prospective studies with guided stereotactic biopsies and correlation of histopathological results.

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  • Accepted: Aug 3, 2017
  • Online: Aug 19, 2017

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