Use of FET PET in glioblastoma patients undergoing neurooncological treatment including tumour-treating fields: initial experience

PurposeWe present our first clinical experience with O-(2-18F-fluoroethyl)-l-tyrosine (FET) PET in patients with high-grade glioma treated with various neurooncological therapies including tumour-treating fields (TTFields) for the differentiation of tumour progression from treatment-related changes.MethodsWe retrospectively assessed 12 patients (mean age 51 ± 12 years, range 33–72 years) with high-grade glioma (11 glioblastomas, 1 gliosarcoma) in whom the treatment regimen included TTFields and who had undergone FET PET scans for differentiation of tumour progression from treatment-related changes. Mean and maximum tumour-to-brain ratios (TBRmean, TBRmax) were calculated. The definitive diagnosis (tumour progression or posttherapeutic changes) was confirmed either by histopathology (4 of 12 patients) or on clinical follow-up.ResultsIn all nine patients with confirmed tumour progression, the corresponding FET PET showed increased uptake (TBRmax 3.5 ± 0.6, TBRmean 2.7 ± 0.7). In one of these nine patients, FET PET was consistent with treatment-related changes, whereas standard MRI showed a newly diagnosed contrast-enhancing lesion. In two patients treated solely with TTFields without any other concurrent neurooncological therapy, serial FET PET revealed a decrease in metabolic activity over a follow-up of 6 months or no FET uptake without any signs of tumour progression or residual tumour on conventional MRI.ConclusionFET PET may add valuable information in monitoring therapy in individual patients with high-grade glioma undergoing neurooncological treatment including TTFields