¹¹ C-methionine PET for differential diagnosis of low-grade gliomas

Abstract

Management of low-grade gliomas continues to be a challenging task, because CT and MRI do not always differentiate from nontumoral lesions. Furthermore, tumor extent and aggressiveness often remain unclear because of a lack of contrast enhancement. Previous studies indicated that large neutral amino acid tracers accumulate in most brain tumors, including low-grade gliomas, probably because of changes of endothelial and blood-brain barrier function. We describe 11C-methionine uptake measured with PET in a series of 196 consecutive patients, most of whom were studied because of suspected low-grade gliomas. Uptake in the most active lesion area, relative to contralateral side, was significantly different among high-grade gliomas, low-grade gliomas, and chronic or subacute nontumoral lesions, and this difference was independent from contrast enhancement in CT or MRI. Corticosteroids had no significant effect on methionine uptake in low-grade gliomas but reduced uptake moderately in high-grade gliomas. Differentiation between gliomas and nontumoral lesions by a simple threshold was correct in 79%. Recurrent or residual tumors had a higher uptake than primary gliomas. In conclusion, the high sensitivity of 11C-methionine uptake for functional endothelial or blood-brain barrier changes suggests that this tracer is particularly useful for evaluation and follow-up of low-grade gliomas.

Early metabolic responses in temozolomide treated low-grade glioma patients

“…At baseline a variable active FET tumor volume was found in 10/11 patients (range 6-273ccm). This is line with earlier reports which describe a lack of increased amino acid uptake in a proportion of LGG [16]. Uptake ratios.…”

Imaging in neurooncology

“…3). 21,86 Uptake is increased not only in solid parts of the tumor but also in the infiltration area. 91,92 In 80% of gliomas WHO II°[ 11 C]MET-uptake is greater than 1.5-fold of the normal brain tissue, 21 whereas glucose metabolism is reduced compared with gray matter.…”

“…21,86 Uptake is increased not only in solid parts of the tumor but also in the infiltration area. 91,92 In 80% of gliomas WHO II°[ 11 C]MET-uptake is greater than 1.5-fold of the normal brain tissue, 21 whereas glucose metabolism is reduced compared with gray matter. Most studies indicated that [ 11 C]MET-uptake is inversely correlated to prognosis, [93][94][95] 78,96 and exceeds the area of involvement depicted by Gd-enhanced MRI.…”

“…21,78,[82][83][84][85][86] The increased methionine uptake (factor of 1.3-3.5 in comparison with a contralateral control region) is related to increased transport mediated by type L amino acid carriers. 87,88 [ 11 C]MET-uptake correlates to cell proliferation in vitro, the expression of Ki-67 and proliferating cell nuclear antigen, as well as to microvessel density, explaining its role as a marker for active tumor proliferation.…”

“…97 It should be pointed out that increased [ 11 C]MET uptake also depends on tumor type, with oligodendrogliomas accumulating more radiotracer than astrocytomas from the same histological grade. 21 100 -103 The overall goal is to be able to quantify chemotherapeutic effects early (within days to weeks).…”