FET PET for the evaluation of untreated gliomas: correlation of FET uptake and uptake kinetics with tumour grading.
OBJECTIVE
Treatment and prognosis of gliomas depend on their histological tumour grade. The aim of the study was to evaluate the potential of [(18)F]fluoroethyltyrosine (FET) PET for non-invasive tumour grading in untreated patients.


METHODS
Dynamic FET PET studies were performed in 54 patients who, based on MRI, were estimated to have low grade (LG; n = 20), intermediate (WHO II-III; n = 4) or high grade (HG; n = 30) tumours. For standard evaluation, tumour SUV(max) and the ratio to background (SUV(max)/BG) were calculated (sum image: 20-40 min). For dynamic evaluation, mean SUV values within a 90% isocontour ROI (SUV90) and the SUV90/BG ratios were determined for each time frame to evaluate the course of FET uptake. Results were correlated with histopathological findings from PET-guided stereotactic biopsies.


RESULTS
Histology revealed gliomas in all patients. Using the standard method a statistically significant difference (p = 0.001) was found between LG (n = 20; SUV(max)/BG: 2.16 +/- 0.98) and HG (n = 34; SUV(max)/BG: 3.29 +/- 1.06) gliomas (opt. threshold 2.58: SN71%/SP85%/area under ROC curve [AUC]:0.798), however, with a marked overlap between WHO II to IV tumours. Time activity curves showed slight increase in LG, whereas HG tumours presented with an early peak (10-20 min) followed by a decrease. Dynamic evaluation successfully separated LG from HG gliomas with higher diagnostic accuracy (SN94%/SP100%/AUC:0.967).


CONCLUSIONS
Based on the ratio-based method, a statistically significant difference was found between LG and HG gliomas. Due to the interindividual variability, however, no reliable individual grading was possible. In contrast, dynamic evaluation allowed LG and HG gliomas to be differentiated with high diagnostic power and, thus, should supplement the conventional method.
Pöpperl
Gabriele
G
Department of Nuclear Medicine, Klinikum Grosshadern, University of Munich, Marchioninistrasse 15, Munich, Germany. Gabriele.Poepperl@med.uni-muenchen.de
Kreth
Friedrich W
FW
Mehrkens
Jan H
JH
Herms
Jochen
J
Seelos
Klaus
K
Koch
Walter
W
Gildehaus
Franz J
FJ
Kretzschmar
Hans A
HA
Tonn
Jörg C
JC
Tatsch
Klaus
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D005910:Glioma / Q000145:classification / Q000175:diagnosis* / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
C117289:O-(2-fluoroethyl)tyrosine; D019275:Radiopharmaceuticals; D014443:Tyrosine