Methyl-L-11C-methionine PET as a diagnostic marker for malignant progression in patients with glioma.

UNLABELLED Methyl-L-(11)C-methionine ((11)C-MET) PET has been shown to detect brain tumors with a high sensitivity and specificity. In this study, we investigated the potential of (11)C-MET PET to noninvasively detect tumor progression in patients with gliomas. Moreover, we analyzed the relationship between changes in (11)C-MET uptake on PET and changes in various molecular immunohistochemical markers during progression of gliomas. METHODS Twenty-four patients with histologically proven glioma were investigated repeatedly with (11)C-MET PET. (11)C-MET uptake was determined for a circular region of interest. Histologic and molecular analyses for tumor progression were performed after open surgery and stereotactic biopsy, respectively. RESULTS In patients with malignant progression, the mean increase in (11)C-MET uptake was 54.4% (SD, 45.5%; range, 3.1%-162.2%), whereas in patients without a change in tumor grade, mean (11)C-MET uptake did not significantly change (3.9%; SD, 13.7%; range, -24.4% to 26.3%). The difference in the change in (11)C-MET uptake between the group with malignant progression and the group without malignant progression was highly significant (P < 0.001). Receiver-operating-curve analysis revealed a sensitivity of 90% and a specificity of 92.3% for the detection of malignant transformation by an increase in (11)C-MET uptake of more than 14.6%. Increased (11)C-MET uptake of more than 14.6% was indicative of malignant progression in all but 3 leave-one-out iterations. A detailed immunohistochemical analysis demonstrated a significant correlation between changes in (11)C-MET uptake and the expression of vascular endothelial growth factor. CONCLUSION These data suggest that (11)C-MET-PET represents a noninvasive method to detect malignant progression in patients with gliomas. Moreover, the increase in (11)C-MET uptake during malignant progression is reflected by an increase in angiogenesis-promoting markers as vascular endothelial growth factor.