engleski

Primary diagnosis of low-grade glioma: F-18-FET or F-18-FCH PET? A pilot study

Aim/Introduction: Gliomas, as one of the more commonly diagnosed primary brain tumours, are associated with variable survival, in part linked with their histological type. The diagnosis of low grade gliomas (LGG) is challenging, as results of radiological imaging modalities can often be inconclusive or equivocal. Functional imaging modalities have been introduced to provide additional metabolic information. O- (2-[18F]- fluoroethyl) -L-tyrosine (18F-FET) is PET radiopharmaceutical approved for the characterisation of glioma-suggestive brain lesions. 18F-FET displays a high tumour-to- background ratio and minimal accumulation in inflammatory lesions. Because of low uptake in healthy brain parenchyma, fluoromethyl-(18F)- dimethyl-2- hydroxyethylammonium chloride (18F- FCH) has also been used for diagnosis of LGG is some european nuclear medicine units. The objective of this pilot study was to investigate the diagnostic accuracy of 18F-FET and 18F-FCH PET in patients with primary LGG. Materials and Methods: Eleven patients aged 21-80 years with MRI-suspected LGG were involved in this study. Patients underwent both 18F-FET and 18F-FCH PET/ CT within one week. Brain PET/CT was performed according to standard protocol: 20 minutes after intravenous injection of 185 MBq of 18F-FET and 185 MBq of 18F-FCH PET. Surgery and histological diagnoses were performed in the next two weeks. Results: Eleven out of 11 patients with suspected LGG underwent MRI, 18F-FET and 18F-FCH PET/CT. All patients had LGG according to MRI. In all PET positive patients, tumour location on MRI was consistent with region of PET/ CT positivity. Nine out of 11 patients with suspected LGG had final histological diagnosis after the surgery. Two out of 11 patients included in this study did not undergo surgery or biopsy for histological confirmation. Both had negative 18F-FET and negative 18F-FCH PET scan, so they declined surgery and multidisciplinary tumour board recommended follow-up. Seven lesions positive on 18F-FET PET and negative on 18F-FCH PET scan were diffuse astrocytoma (grade II), ganglioma (grade I) and anaplastic astrocytoma (grade III) by pathohistology. Two lesions positive on 18F-FET PET and positive on 18F-FCH PET scan were glioblastoma multiforme (grade IV) by pathohistology. Conclusion: Preliminary results on a small patient sample suggest appropriate radiopharmaceutical should be chosen before performing PET/CT scan in patients with newly diagnosed LGG. 18F-FET is more accurate radiopharmaceutical than 18F-FCH in detection of LGG, while increased lipid synthesis seems to correlate with higher grade and more aggressive gliomas.

F-18-choline ; glioma ; F-18-FET

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