Comparison of (18)F-FET and (18)F-FDG PET in brain tumors.
The purpose of this study was to compare the diagnostic value of positron emission tomography (PET) using [(18)F]-fluorodeoxyglucose ((18)F-FDG) and O-(2-[(18)F]fluoroethyl)-l-tyrosine ((18)F-FET) in patients with brain lesions suspicious of cerebral gliomas.


METHODS
Fifty-two patients with suspicion of cerebral glioma were included in this study. From 30 to 50 min after injection of 180 MBq (18)F-FET, a first PET scan ((18)F-FET scan) was performed. Thereafter, 240 MBq (18)F-FDG was injected and a second PET scan was acquired from 30 to 60 min after the second injection ((18)F-FET/(18)F-FDG scan). The cerebral accumulation of (18)F-FDG was calculated by decay corrected subtraction of the (18)F-FET scan from the (18)F-FET/(18)F-FDG scan. Tracer uptake was evaluated by visual scoring and by lesion-to-background (L/B) ratios. The imaging results were compared with the histological results and prognosis.


RESULTS
Histology revealed 24 low-grade gliomas (LGG) of World Health Organization (WHO) Grade II and 19 high-grade gliomas (HGG) of WHO Grade III or IV, as well as nine others, mainly benign histologies. The gliomas showed increased (18)F-FET uptake (>normal brain) in 86% and increased (18)F-FDG uptake (>white matter) in 35%. (18)F-FET PET provided diagnostically useful delineation of tumor extent while this was impractical with (18)F-FDG due to high tracer uptake in the gray matter. A local maximum in the tumor area for biopsy guidance could be identified with (18)F-FET in 76% and with (18)F-FDG in 28%. The L/B ratios showed significant differences between LGG and HGG for both tracers but considerable overlap so that reliable preoperative grading was not possible. A significant correlation of tracer uptake with overall survival was found with (18)F-FDG only. In some benign lesions like abscesses, increased uptake was observed for both tracers indicating a limited specificity of both techniques.


CONCLUSIONS
(18)F-FET PET is superior to (18)F-FDG for biopsy guidance and treatment planning of cerebral gliomas. The uptake of (18)F-FDG is associated with prognosis, but the predictive value is limited and a histological evaluation of tumor tissue remains necessary. Therefore, amino acids like (18)F-FET are the preferred PET tracers for the clinical management of cerebral gliomas.
Pauleit
Dirk
D
Institute of Neuroscience and Medicine, Forschungszentrum Jülich, D-52425 Jülich, Germany.
Stoffels
Gabriele
G
Bachofner
Ansgar
A
Floeth
Frank W
FW
Sabel
Michael
M
Herzog
Hans
H
Tellmann
Lutz
L
Jansen
Paul
P
Reifenberger
Guido
G
Hamacher
Kurt
K
Coenen
Heinz H
HH
Langen
Karl-Josef
KJ
D000293:Adolescent; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D014443:Tyrosine / Q000031:analogs & derivatives*; D055815:Young Adult
C117289:O-(2-fluoroethyl)tyrosine; D019788:Fluorodeoxyglucose F18; D014443:Tyrosine