18F-FDOPA PET Imaging of Brain Tumors: Comparison Study with 18F-FDG PET and Evaluation of Diagnostic Accuracy

摘要

id="p-1">We evaluated the amino acid and glucose metabolism of brain tumors by using PET with 3,4-dihydroxy-6-18F-fluoro- class="sc">l-phenylalanine (18F-FDOPA) and 18F-FDG. >Methods: Eighty-one patients undergoing evaluation for brain tumors were studied. Initially, 30 patients underwent PET with 18F-FDOPA and 18F-FDG within the same week. Tracer kinetics in normal brain and tumor tissues were estimated. PET uptake was quantified by use of standardized uptake values and the ratio of tumor uptake to normal hemispheric tissue uptake (T/N). In addition, PET uptake with 18F-FDOPA was quantified by use of ratios of tumor uptake to striatum uptake (T/S) and of tumor uptake to white matter uptake. The accuracies of 18F-FDOPA and 18F-FDG PET were determined by comparing imaging data with histologic findings and findings of clinical follow-up of up to 31 mo (mean, 20 mo). To further validate the accuracy of 18F-FDOPA PET, 18F-FDOPA PET was performed with an additional 51 patients undergoing brain tumor evaluation. >Results: Tracer uptake in tumors on 18F-FDOPA scans was rapid, peaking at approximately 15 min after intravenous injection. Tumor uptake could be distinguished from that of the striatum by the difference in peak times. Both high-grade and low-grade tumors were well visualized with 18F-FDOPA. The sensitivity for identifying tumors was substantially higher with 18F-FDOPA PET than with 18F-FDG PET at comparable specificities, as determined by simple visual inspection, especially for the assessment of low-grade tumors. Using receiver-operating-characteristic curve analysis, we found the optimal threshold for 18F-FDOPA to be a T/S of greater than 1.0 (sensitivity, 96%; specificity, 100%) or a T/N of greater than 1.3 (sensitivity, 96%; specificity, 86%). The high diagnostic accuracy of 18F-FDOPA PET at these thresholds was confirmed with the additional 51 patients (a total of 81 patients: sensitivity, 98%; specificity, 86%; positive predictive value, 95%; negative predictive value, 95%). No significant difference in tumor uptake on 18F-FDOPA scans was seen between low-grade and high-grade tumors (P = 0.40) or between contrast-enhancing and nonenhancing tumors (P = 0.97). Radiation necrosis was generally distinguishable from tumors on 18F-FDOPA scans (P 0.00001). >Conclusion: 18F-FDOPA PET was more accurate than 18F-FDG PET for imaging of low-grade tumors and evaluating recurrent tumors. 18F-FDOPA PET may prove especially useful for imaging of recurrent low-grade tumors and for distinguishing tumor recurrence from radiation necrosis.