Non-invasive grading of brain tumours using dynamic amino acid PET imaging: does it work for 11C-methionine?
BACKGROUND
Static imaging of amino acids does not allow differentiation of low versus high grade brain tumours. It has been shown that dynamic imaging of the amino acid analogue (18)F-fluoroethyltyrosine (FET) can achieve this goal. In many centres, (11)C-methionine (MET) is used for tumour imaging, but no clinical studies on the use of dynamic scanning for grading have been performed.


METHODS
Thirty-four patients with primary brain glioma and histopathological confirmation were retrospectively studied using 40 min dynamic MET-PET with 220 MBq 11C-methionine. In relation to histopathological grading, various metabolic indices and temporal parameters as documented by Poepperl et al. (JNM 2006;47:393-403) were analyzed.


RESULTS
None of the evaluated static or temporal parameters allowed discrimination between high and low grade tumours. On average, low grade tumours showed washout after the initial uptake maximum, while both increases and decreases were seen for high grade tumours. Only the relative early versus late uptake ratio showed a trend towards significance (-0.16 +/- 0.17 for low grade versus 0.01 +/- 0.25 for high grade; p = 0.07).


CONCLUSIONS
Unlike FET-PET, the uptake characteristics of MET-PET do not allow classification of low and high grade tumours on an individual patient basis. Since literature data indicate that both tracers have a similar performance regarding biopsy location, tumour delineation, and detection of recurrence, FET-PET should be advocated over MET-PET as its uptake mechanism also allows noninvasive grading in glioma.
Moulin-Romsée
Gérard
G
Division of Nuclear Medicine, University Hospital Leuven and K.U. Leuven, Herestraat 49, Leuven, Belgium.
D'Hondt
Eduard
E
de Groot
Tjibbe
T
Goffin
Jan
J
Sciot
Raf
R
Mortelmans
Luc
L
Menten
Johan
J
Bormans
Guy
G
Van Laere
Koen
K
D000293:Adolescent; D000328:Adult; D001932:Brain Neoplasms / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology*; D002648:Child; D005260:Female; D005910:Glioma / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D008297:Male; D008715:Methionine; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
D019275:Radiopharmaceuticals; C086242:carbon-11 methionine; D008715:Methionine