The in vivo metabolic pattern of low-grade brain gliomas: a positron emission tomographic study using 18F-fluorodeoxyglucose and 11C-L-methylmethionine.
OBJECTIVE
The object of the present study was to identify metabolic differences between low-grade astrocytomas and oligodendrogliomas and to improve their diagnosis and noninvasive assessment, because both types of tumors look very similar from the point of view of clinical and radiological data (as assessed by computed tomography and magnetic resonance imaging).


METHODS
Before any aggressive treatment, 22 patients with primary low-grade gliomas (astrocytomas in 12 patients and oligodendrogliomas in 10) were investigated with positron emission tomography for both glucose metabolism (18F-fluorodeoxyglucose) and amino acid uptake (11C-L-methylmethionine). An original software that allows a full metabolic analysis of the tumor region of interest (defined from the T1-weighted magnetic resonance image) and compares tumor tissue uptake tracer concentrations with average healthy tissue values has been implemented for data processing. Heterogeneity of each individual tumor has been taken into account and was expressed in histograms, which provided data about the mean and also extreme and intermediate values of tracer concentrations and the way these values are distributed among the full tumor mass.


RESULTS
It has been shown that both tumor types exhibit a glucose hypometabolism (slightly more pronounced with astrocytomas), whereas they strongly differ in methionine uptake, which is high in all oligodendrogliomas and either decreased, normal, or moderately increased in astrocytomas. This latter metabolic difference between both tumor populations may be partially explained by their different cell densities.


CONCLUSIONS
This study suggests that despite similar radiological and clinical presentations, these two kinds of low-grade gliomas are metabolically different and could therefore have specific responses to different therapies. Moreover, their in vivo metabolic follow-up with positron emission tomography should rely on different parameters, depending on their histological type; methionine uptake may be more relevant than glucose metabolism in the follow-up of oligodendrogliomas.
Derlon
J M
JM
CYCERON (Cyclotron Biomedical de Caen, CEA/DSV, CNRS, INSERM) CHU, France.
Petit-Taboué
M C
MC
Chapon
F
F
Beaudouin
V
V
Noël
M H
MH
Creveuil
C
C
Courtheoux
P
P
Houtteville
J P
JP
D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000378:metabolism*; D001254:Astrocytoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D001786:Blood Glucose / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D003847:Deoxyglucose / Q000031:analogs & derivatives / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D005910:Glioma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D009837:Oligodendroglioma / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
D000596:Amino Acids; D001786:Blood Glucose; D019788:Fluorodeoxyglucose F18; D003847:Deoxyglucose; D008715:Methionine; C038344:methionine methyl ester