Correlation of 6-18F-Fluoro-L-Dopa PET Uptake with Proliferation and Tumor Grade in Newly Diagnosed and Recurrent Gliomas

6-F-18-fluoro-L-dopa (F-18-FDOPA) measured with PET as a bio-marker of amino acid uptake has been investigated in brain tumor imaging. The aims of the current study were to determine whether the degree of F-18-FDOPA uptake in brain tumors predicted tumor grade and was associated with tumor proliferative activity in newly diagnosed and recurrent gliomas. Methods: Fifty-nine patients (40 men, 19 women; mean age +/- SD, 44.4 +/- 12.3 y) with newly diagnosed (n = 22) or recurrent (n = 37) gliomas underwent F-18-FDOPA PET perioperatively. Tumor tissue was obtained by resection or biopsy in all patients. The tumor grade and Ki-67 proliferation index were obtained by standard pathology assays. Tumor F-18-FDOPA uptake was quantified by determining various standardized uptake value (SUV) parameters (mean SUV, maximum SUV [SUVmax], mean values of voxels with top 20% SUVs, and tumor-to-normal-brain tissue ratios) that were then correlated with histopathologic grade and Ki-67 proliferation index. Results: Fifty-nine lesions in 59 patients were analyzed. F-18-FDOPA uptake was significantly higher in high-grade than in low-grade tumors for newly diagnosed tumors (SUVmax, 4.22 +/- 1.30 vs. 2.34 +/- 1.35, P = 0.005) but not for recurrent tumors that had gone through treatment previously (SUVmax, 3.36 +/- 1.26 vs. 2.67 +/- 1.18, P = 0.22). An SUVmax threshold of 2.72 differentiated low-grade from high-grade tumors, with a sensitivity and specificity of 85% and 89%, respectively, using receiver-operating-characteristic curve analysis (area under the curve, 0.86). F-18-FDOPA PET uptake correlated significantly with Ki-67 tumor proliferation index in newly diagnosed tumors (r = 0.66, P = 0.001) but not in recurrent tumors (r = 0.14, P = 0.41). Conclusion: F-18-FDOPA uptake is significantly higher in high-grade than in low-grade tumors in newly diagnosed but not recurrent tumors that had been treated previously. A significant correlation between F-18-FDOPA uptake and tumor proliferation in newly diagnosed tumors was observed, whereas this correlation was not identified for recurrent tumors. Thus, F-18-FDOPA PET might serve as a noninvasive marker of tumor grading and might provide a useful surrogate of tumor proliferative activity in newly diagnosed gliomas.