Abstract
We retrospectively evaluated the usefulness of combined measurement of L-methyl-[11C]methionine (MET) and 3'-deoxy-3'-[18F]fluorothymidine (FLT) positron emission tomography (PET) in the differential diagnosis between recurrent gliomas and necrotic lesions. Twenty-one patients with high-grade glioma, previously treated with surgery and radiotherapy with chemotherapy and first radiological suspicion of recurrence were enrolled. The uptake was assessed by the maximum standardized uptake value (SUVmax) and lesion-to-normal tissue count density ratio (L/N ratio). Of the 21 lesions, 15 were diagnosed recurrent gliomas and six were necrotic lesions. The average SUVmax was not significantly different between recurrent gliomas and necrotic lesions on either MET-PET or FLT-PET. The average L/N ratio of recurrent gliomas (3.36 ± 1.06) was significantly higher than that of necrotic lesions (2.18 ± 0.66) on MET-PET (p < 0.01) and the average L/N ratio of recurrent gliomas (7.01 ± 2.26) was also significantly higher than that of necrotic lesions (4.60 ± 1.23) on FLT-PET (p < 0.01). ROC curve analysis showed that the areas under the curves were high but not different between MET- and FLT-PET. PET studies using MET and FLT are useful in the differentiation of recurrent glioma from treatment-induced necrotic lesion. However, there is no complementary information in the differentiation with simultaneous measurements of MET- and FLT-PET.
Highlights
Recurrence in glioma may occur after macroscopic total removal of tumor or stabilization of tumor with treatment
The MET uptake of one necrotic lesion (Case 19) was faint compared to the normal brain parenchyma (L/N ratio of 1.25)
When we evaluate 13 patients (10 recurrent gliomas and three necrotic lesions) whose diagnosis was confirmed with histopathology, the results are similar to those in all patients
Summary
Recurrence in glioma may occur after macroscopic total removal of tumor or stabilization of tumor with treatment. PET with L-methyl-[11C]methionine (MET) is a well-established imaging tool for brain tumour detection [4], tumour grading [5,6,7], prediction of prognosis [6,8,9], evaluation of response to treatment [10,11,12,13], and differentiation between tumor recurrence and radiation necrosis [14,15] in patients with gliomas. A recent study shows that FLT-PET has a high sensitivity but a low specificity, which has a limited role in the diagnosis of recurrent gliomas [25] This retrospective study was conducted to evaluate the usefulness of combined use of MET-PET and FLT-PET in the differential diagnosis between recurrent gliomas and treatment-induced necrotic lesions
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