Positron emission tomography imaging of meningioma in clinical practice: review of literature and future directions.
ABSTRACT Meningiomas represent about 20% of intracranial tumors and are the most frequent nonglial primary brain tumors. Diagnosis is based on computed tomography (CT) and magnetic resonance imaging (MRI). Mainstays of therapy are surgery and radiotherapy. Adjuvant chemotherapy is tested in clinical trials of phase II. Patients are followed clinically by imaging. However, classical imaging modalities such as CT and MRI have limitations. Hence, we need supplementary imaging tools. Molecular imaging modalities, especially positron emission tomography (PET), represent promising new instruments that are able to characterize specific metabolic features. So far, these modalities have only been part of limited study protocols, and their impact on clinical routine management is still under investigation. It may be expected that their extended use will provide new aspects about meningioma imaging and biology. In the present article, we summarize PET imaging for meningiomas based on a thorough review of the literature. We discuss and illustrate the potential role of PET imaging in the clinical management of meningiomas. Finally, we indicate current limitations and outline directions for future research.
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ABSTRACT: Fluoro-deoxyglucose positron emission tomography (FDG PET) enables the in vivo study of tissue metabolism, and thus is able to identify malignant tumours as hypermetabolic lesions by an increase in tracer uptake. Many papers have demonstrated both the relevant impact of FDG PET on staging of many cancers and the superior accuracy of the technique compared with conventional diagnostic methods for pre-treatment evaluation, therapy response evaluation and relapse identification. In particular PET was found useful in identifying lymph nodal and metastatic spread, thus altering patient management in more than 30% of cases. PET images, however, provide limited anatomical data, which in regions such as the head and neck, mediastinum and pelvic cavity is a significant drawback. The exact localization of lesions may also be difficult in some cases on the basis of PET images alone. The introduction of combined PET-computed tomography (PET-CT) scanners enables the almost simultaneous acquisition of transmission and emission images, thus obtaining optimal fusion images in a very short time. PET-CT fusion images enable lesions to be located, reducing false positive studies and increasing accuracy; the overall duration of the examination may also be reduced. On the basis of both literature data and our experience we established the clinical indications when PET-CT may be particularly useful, in comparison with PET alone. It should also be underlined that the use of PET-CT is almost mandatory for new tracers such as 11C-choline and 11C-methionine; these new tracers may be applied for studying tumours not assessable with FDG, such as prostate cancer. In conclusion PET-CT is at present the most advanced method for metabolic imaging, and is capable of precisely localizing and assessing tumours; fusion images reduce false positive and inconclusive studies, thus increasing diagnostic accuracy.La radiologia medica 110(1-2):1-15. · 1.46 Impact Factor
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ABSTRACT: Somatostatin receptor scintigraphy (SRS) using 111In-octreotide has proven useful in the preoperative discrimination of expansive central nervous system lesions. Meningiomas, generally expressing human somatostatin receptor (hsst) on their surface, were detected with a sensitivity of about 100%. This finding was associated with the assumption that meningiomas lack an intact blood-brain barrier. However, this exclusion procedure became questionable when histologically proven meningiomas in which SRS was negative were reported. Therefore, the aim of this study was to discover why these meningiomas gave negative SRS results. Before surgery, 46 patients with 47 meningiomas underwent standard MRI and SRS. Thirty-four of these patients with 35 tumors were also examined by 99mTc-diethylenetriaminepentaacetic acid (DTPA) brain scintigraphy. After surgical resection, hsst subtype 2 (hsst2) messenger RNA (mRNA) expression of 4 SRS-positive and 4 SRS-negative meningiomas was estimated semiquantitatively by reverse transcriptase polymerase chain reaction (RT-PCR). Translation of hsst2 mRNA into receptor proteins was proven immunocytochemically on the surface of 1 SRS-positive and 1 SRS-negative meningioma. Tumor specimens used for RNA extraction and RT-PCR and cultivated cells used for hsst2 immunostaining were tested for their meningioma nature by immunochemistry. SRS yielded positive results in 39 meningiomas with a tumor volume of 24.1 +/- 32.8 mL and negative results in 8 meningiomas with a volume of 3.9 +/- 6.5 mL. 99mTc-DTPA scintigraphy visualized 24 of 35 meningiomas. SRS was positive in all of them. In contrast, 11 meningiomas were (99mTc-DTPA negative. In these meningiomas, SRS was negative in 5 cases (5.4 +/- 8.1 mL), whereas the remaining 6 were positive (4.6 +/- 4.5 mL). None of the meningiomas was 99mTc-DTPA positive and SRS negative. RT-PCR revealed no significant difference of hsst2 mRNA expression between SRS-positive and SRS-negative meningiomas but showed varied expression among all meningiomas regardless of SRS results. Furthermore, hsst2 proteins were visualized immunocytochemically on the surface of cultivated cells of SRS-positive and SRS-negative meningiomas. SRS-negative meningiomas do express hsst2; thus, in these meningiomas SRS is false-negative. Because an insufficient sensitivity was excluded, 99mTc-DTPA scintigraphy identified a permeability barrier in SRS-negative meningiomas that explains their false-negative SRS results. SRS-negative meningiomas most likely meet the function of their tissue of origin (the meninges) to develop more-or-less intact permeability barriers.Journal of Nuclear Medicine 10/2001; 42(9):1338-45. · 5.77 Impact Factor
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ABSTRACT: We investigated the use of PET with 2[18F]fluoro-2-deoxy-D-glucose (FDG) to discriminate between atypical or malignant and grade 1 meningiomas. The influence of fasting state and high-dose corticosteroid medication was analyzed retrospectively. Preoperative PET scans of 75 patients with suspected diagnosis of intracranial meningioma were evaluated using standardized uptake values (SUV) and tumor-to-contralateral gray matter ratios (TGR) of FDG uptake. Fifty-one of 75 patients fasted before the PET scan, and 27 of 75 patients were studied under high-dose corticosteroid medication. Eighteen tumors had recurred. PET results were compared to histopathological grading. PET correctly identified 8/9 atypical or malignant meningiomas and 58/66 grade 1 meningiomas using TGR and a threshold of 1.05 in primary meningioma and 0.85 in tumor recurrence. This corresponds to a specificity of 0.88 for the detection of higher tumor grading. Specificity was significantly higher in fasting compared to nonfasting subjects (0.96 versus 0.73; p < 0.025). SUV quantification lead to a reduced specificity of 0.77 at the same level of sensitivity. The only false-negative PET finding occurred in a recurrent meningioma, which had been operated on four times before. Overnight fasting before injection is needed to improve the diagnostic accuracy of FDG-PET for noninvasive metabolic grading of meningioma. Hyperglycemia in nonfasting patients and in diabetic patients may lead to overestimation of meningioma grading.Journal of Nuclear Medicine 02/1997; 38(1):26-30. · 5.77 Impact Factor