Metabolic characterization of childhood brain tumors: comparison of 18F-fluorodeoxyglucose and 11C-methionine positron emission tomography.
BACKGROUND
Positron emission tomography (PET) scans of primary brain tumors were performed in pediatric patients to examine whether metabolic characteristics could be used as an index of clinical aggressiveness.


METHODS
Twenty-seven pediatric patients with untreated primary central nervous system neoplasms were studied with PET scans using 2-[(18)F] fluoro-2-deoxy-D-glucose (FDG) and/or L-[methyl-(11)C] methionine (MET). Metabolic characteristics as assessed with FDG and MET standardized uptake values (SUV) and SUV-to-normal brain ratios were compared with histopathology and selected histochemical features such as proliferation activity (Ki-67(MIB-1)) and apoptotic, vascular, and cell density indices. The median followup time was 43 months.


RESULTS
The accumulation of both FDG and MET was significantly higher in high-grade than in low-grade tumors, but a considerable overlap was found. The accumulation of both tracers was associated positively with age. High-grade tumors showed higher proliferative activity and vascularity than the low-grade tumors. In univariate analysis, FDG-PET, MET-PET, and apoptotic index were independent predictors of event-free survival.


CONCLUSIONS
We found that both FDG and MET uptake in pediatric brain tumors are associated with malignancy grade. However, no clear limits of SUVs and SUV-to-normal brain ratios can be set between low-grade and high-grade tumors, which makes the assessment of malignancy grade using metabolic imaging with PET scan difficult in individual cases. Although FDG-PET and MET-PET do not compensate for histopathologic evaluation, they may give valuable additional information especially if invasive procedures to obtain histopathologic samples are not feasible.
Utriainen
Meri
M
Turku PET Centre, University of Turku, Finland. meri.utriainen@hus.fi
Metsähonkala
Liisa
L
Salmi
Toivo T
TT
Utriainen
Tapio
T
Kalimo
Hannu
H
Pihko
Helena
H
Mäkipernaa
Anne
A
Harila-Saari
Arja
A
Jyrkkiö
Sirkku
S
Laine
Jukka
J
Någren
Kjell
K
Minn
Heikki
H
D000293:Adolescent; D000367:Age Factors; D017209:Apoptosis; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D002250:Carbon Radioisotopes; D002648:Child; D002675:Child, Preschool; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007223:Infant; D008297:Male; D008715:Methionine; D019275:Radiopharmaceuticals; D014055:Tomography, Emission-Computed
D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D008715:Methionine