Association of F18-fluoro-ethyl-tyrosin uptake and 5-aminolevulinic acid-induced fluorescence in gliomas
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Malignant gliomas are highly infiltrative tumours with a fatal prognosis. F18-fluoroethyl-tyrosine (FET)-positron emission tomography (PET) often reveals a broader extension of these tumours compared with contrast-enhanced magnetic resonance imaging (MRI). Complete resection of the contrast-enhancing lesion is aspired. Fluorescence-guided resection using 5-aminolevulinic acid (5-ALA) improved the extent of resection. In this study, we investigated whether the FET uptake correlates with the extent of resection using 5-ALA-induced fluorescence.
Thirteen patients who underwent preoperative and postoperative MRI, FET-PET and fluorescence-guided neuronavigated resection were included in this study. The areas in which intraoperative fluorescence terminated the resection were marked. After fusion of PET and MRI, the standardized uptake value (SUV) of FET related to normal brain (SUVR) was measured in regions of interest corresponding to resected and remaining tissue, respectively. Receiver-operating characteristic (ROC) curve analysis determined the optimal threshold of the relative SUV anticipating 5-ALA-induced fluorescence.
During resection a vivid fluorescence was present in all patients. Histology revealed glioblastomas in 11 cases, an anaplastic astrocytoma in one case and a low-grade astrocytoma in one case. The median FET SUVR was higher in areas corresponding to the fluorescent tumour compared with the non-fluorescent normal brain (2.321 vs 1.142, p < 0.0001, t-test). A SUVR greater than 1.374 predicted the fluorescence with a sensitivity of 0.87 [95% confidence interval (CI): 0.74–0.94] and a specificity of 0.94 (CI: 0.84–0.99). The area under the ROC curve was 0.9656 (CI: 0.9364–0.9948).
FET uptake predicts the 5-ALA-induced fluorescence in glioma patients. Thus, FET-PET provides useful information for planning glioma resection.