[11C]L-methionine uptake in gliomas

Treatment of gliomas remains disappointing in spite of a great number of experimental biological data and of randomized therapeutic studies. This could be partly explained by the inefficiency of our conventional methods to assess the regional metabolism of these tumors. The use of positron emission tomography (PET) brings encouraging possibilities in this field. We report our preliminary experience of measuring regional cerebral methionine uptake with PET after intravenous injection of [11C]L-methionine. Twenty-two patients with histologically confirmed gliomas were studied. An ECAT II positron emission tomograph was used for scanning. The position of the plane was chosen to include a major section of the tumor in the reconstructed brain slice. The protocol required a two-step examination: 1) after injection of 15 to 25 mCi of [11C]L-methionine, 12 scans were performed over a period of 46 minutes; and 2) 18 hours later, regional cerebral blood volume was measured in the same slice after intravenous injection of 2 to 4 mCi of 68GaCl3. The tumoral region of interest was determined as being the area of maximum activity. For each patient we calculated the ratio, R, between the activity in this tumor region of interest and the activity in the contralateral healthy symmetric region of interest which was used as an "internal standard" for the same patient. We correlated the ratio R with the histological grading. In 22 patients, mean values of R were calculated for each tumor: Grade II (n = 5): R = 1.04 +/- 0.27; Grade III (n = 5): R = 1.68 +/- 0.22; and Grade IV (n = 12): R = 2.33 +/- 0.86.(ABSTRACT TRUNCATED AT 250 WORDS)