Direct comparison of 18F-FDG and 11C-methionine PET in suspected recurrence of glioma: sensitivity, inter-observer variability and prognostic value.
OBJECTIVE
18F-fluorodeoxyglucose (FDG) and 11C-methionine (MET) PET imaging studies allow the investigation of metabolism and amino acid transport in brain tumours. Their (relative) usefulness and prognostic value in suspected recurrence or progression of primary brain tumours after previous therapy is an issue of debate. The aim of this study was to compare directly both radioligands in this setting.


METHODS
Cerebral uptake of FDG and MET was determined sequentially on the same day in 30 patients (21 males, nine females; age 40.4+/-15.6 years), on average 4.0 years (range 0.1-18) after therapy for a primary brain tumour (23 grade II-IV astrocytomas, four oligodendrogliomas and three mixed oligo-astrocytomas). Images were acquired on a Siemens HR+ dedicated PET camera. Two observers scored FDG and MET scans independently. Semi-quantitative indices defined by the tumour (maximum)-to-background ratio were calculated based on manual ROI delineation and by using MET ROIs for FDG after automated co-registration. Patient follow-up was conducted until the last contact with inconspicuous clinical findings (average 41 months, range 12-62 months after PET) [(n=10)] or until death (n=20).


RESULTS
Overall median survival was 15.0 months. MET showed pathologically increased uptake in 28/30 scans, and FDG in 17/30. The inter-observer agreement was 100% for MET and 73% for FDG. Using Kaplan-Meier survival analysis, significant differences were found for both FDG (cut-off 0.8, log-rank p=0.007) and MET (cut-off 2.2, log-rank p=0.014). The combination of FDG and MET information resulted in the highest prognostic accuracy (p=0.003), while MET alone was the best prognostic predictor in the subgroup of patients with primary astrocytoma (n=23).


CONCLUSIONS
FDG and MET PET studies provide complementary prognostic information in patients with suspected brain tumour recurrence or progression after primary therapy. MET is considered the single agent of choice in the evaluation of these patients because of its sensitivity and clearer delineation of the suspected recurrence.
Division of Nuclear Medicine, University Hospital Leuven, Herestraat 49, 3000, Leuven, Belgium. koen.vanlaere@uz.kuleuven.ac.be
Koen
K
Van Laere
Sarah
S
Ceyssens
Frank
F
Van Calenbergh
Tjibbe
T
de Groot
Johan
J
Menten
Patrick
P
Flamen
Guy
G
Bormans
Luc
L
Mortelmans
D000293:Adolescent; D000328:Adult; D000368:Aged; D001530:Belgium / Q000453:epidemiology; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality* / Q000628:therapy; D002648:Child; D005260:Female; D019788:Fluorodeoxyglucose F18; D005910:Glioma / Q000000981:diagnostic imaging* / Q000401:mortality* / Q000628:therapy; D006801:Humans; D008297:Male; D008715:Methionine; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000401:mortality*; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods / Q000706:statistics & numerical data; D015995:Prevalence; D011379:Prognosis; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016019:Survival Analysis
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine