Non selective transport of [11C-methyl]-L-and D-methionine into a malignant glioma

Images obtained by X-ray CT, brain scintigraphy (99mTc-DTPA) and positron emission tomography (PET) with [11C-methyl]-L- and D-methionine in a case of malignant glioma are presented, showing good agreement of PET and CT findings, in particular nearly identical localization of L- and D-methionine accumulation, whereas the blood brain barrier is only slightly disturbed. In a greater number of patients the amount of accumulated stereoisomers do not differ on a significant level, indicating that a raised transport rate mediated by a carrier of low stereospecifity seems to contribute substantially to the increased uptake of [11C-methyl]-L-methionine in human brain tumors. Several cerebral functions and diseases have been studied with positron emission tomography (PET), which represents a clinical tool for visualizing metabolic activities rather than morphologic lesions (Reivich et al. 1985; Mazziotta et al. 1986). With regard to the malignancy of brain tumors DiChiro et al. (1982, 1984, 1985a, b) showed a correlation between tumor grade and its glucose metabolism measured with 18F-fluorodeoxyglucose. An increased uptake of [11C-methyl]-L-methionine into tumor tissue has also been described (Hübner et al. 1980; Bergström et al. 1983; Kubota et al. 1984; Meyer et al. 1985; Schober et al. 1986b). Bustany et al. (1981, 1983, 1985a, b, 1986) developed a model for quantitative determination of protein synthesis, postulating that methionine incorporation into protein in brain tumors correlates with grade of malignancy. We do not believe that the uptake of [11C-methyl]-L-methionine mainly reflects protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)