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Background Tumor hypoxia and glycolysis have been recognized as determinant factors characterizing tumor aggressiveness in malignant gliomas. To clarify in vivo hypoxia and glucose metabolism in relation to isocitrate dehydrogenase (IDH) mutation and chromosome 1p and 19q (1p/19q) codeletion status, we retrospectively analyzed hypoxia as assessed by positron emission tomography (PET) with [18F]-fluoromisonidazole (FMISO) and glucose metabolism as assessed by PET with [18F]-fluoro-2-deoxy-d-glucose (FDG) in newly diagnosed malignant gliomas. Methods In total, 87 patients with newly diagnosed supratentorial malignant (WHO grade III and IV) gliomas were enrolled in this study. They underwent PET studies with FMISO and FDG before surgery. The molecular features and histopathological diagnoses based on the 2016 WHO classification were determined using surgical specimens. Maximal tumor-to-normal ratio (TNR) was calculated for FDG PET, and maximal tumor-to-blood SUV ratio (TBR) was calculated for FMISO PET. The PET uptake values in relation to IDH mutation and 1p/19q codeletion status were statistically analyzed. Results In all tumors and malignant astrocytomas, the median FMISO TBR in IDH-wildtype tumors was significantly higher than that in IDH-mutant tumors (P P IDH-wildtype tumors tended to be higher than that in IDH-mutant tumors, but the difference was not statistically significant. In WHO grade III anaplastic astrocytomas, there were no significant differences in median FMISO TBR or FDG TNR between IDH-mutant and IDH-wildtype tumors. In IDH-mutant WHO grade III anaplastic gliomas, there were no significant differences in median FMISO TBR or FDG TNR between anaplastic astrocytomas and anaplastic oligodendrogliomas. Conclusions Tumor hypoxia as assessed by FMISO PET was informative for prediction of the IDH mutation status in newly diagnosed malignant gliomas. However, the accuracy of the discrimination was not satisfactory for clinical application. On the other hand, glucose metabolism as assessed by FDG PET could not differentiate the IDH-mutant status. Moreover, PET studies using FMISO and FDG could not predict IDH mutation and 1p/19q codeletion status in WHO grade III tumors.

Background The molecular diagnosis of gliomas such as isocitrate dehydrogenase (IDH) status (wild-type [wt] or mutation [mut]) is especially important in the 2016 World Health Organization (WHO) classification. Positron emission tomography (PET) has afforded molecular and metabolic diagnostic imaging. The present study aimed to define the interrelationship between the 2016 WHO classification of gliomas and the integrated data from PET images using multiple tracers, including 18F-fluorodeoxyglucose (18F-FDG), 11C-methionine (11C-MET), 18F-fluorothymidine (18F-FLT), and 18F-fluoromisonidazole (18F-FMISO). Methods This retrospective, single-center study comprised 113 patients with newly diagnosed glioma based on the 2016 WHO criteria. Patients were divided into 4 glioma subtypes (Mut, Codel, Wt, and glioblastoma multiforme [GBM]). Tumor standardized uptake value (SUV) divided by mean normal cortical SUV (tumor–normal tissue ratio [TNR]) was calculated for 18F-FDG, 11C-MET, and 18F-FLT. Tumor–blood SUV ratio (TBR) was calculated for 18F-FMISO. To assess the diagnostic accuracy of PET tracers in distinguishing glioma subtypes, a comparative analysis of TNRs and TBR as well as the metabolic tumor volume (MTV) were calculated by Scheffe's multiple comparison procedure for each PET tracer following the Kruskal–Wallis test. Results The differences in mean 18F-FLT TNR and 18F-FMISO TBR were significant between GBM and other glioma subtypes (P < .001). Regarding the comparison between Gd-T1WI volumes and 18F-FLT MTVs or 18F-FMISO MTVs, we identified significant differences between Wt and Mut or Codel (P < .01). Conclusion Combined administration of 4 PET tracers might aid in the preoperative differential diagnosis of gliomas according to the 2016 WHO criteria.

Background The molecular features of isocitrate dehydrogenase (IDH) mutation and chromosome 1p and 19q (1p/19q) codeletion status have pivotal role for differentiating gliomas and have been integrated in the World Health Organization (WHO) classification in 2016. Positron emission tomography (PET) with 3′-deoxy-3′-[18F]fluorothymidine (FLT) has been used to evaluate tumour grade and proliferative activity and compared with l-[methyl-11C]-methionine (MET) in glioma patients. Herein, we evaluated tracer uptakes of MET-PET/CT and FLT-PET/CT for differentiating glioma based on the 2016 WHO classification especially in relation to IDH1 mutation status. Methods In total, 81 patients with newly diagnosed supratentorial glioma were enrolled in this study. They underwent PET/CT studies with MET and FLT before surgery. The molecular features and histopathological diagnosis based on the 2016 WHO classification were determined using surgical specimens. The ratios of the maximum standardized uptake value (SUV) of the tumours to the mean SUV of the contralateral cortex (T/N ratios) were calculated on MET-PET/CT and FLT-PET/CT images. Results The mean T/N ratios of MET-PET/CT and FLT-PET/CT in IDH1-wildtype tumours were significantly higher than those in IDH1-mutant tumours (P < 0.001 and P < 0.001, respectively). Receiver operating characteristic analysis for differentiating IDH1 mutation status showed that the area under the curve of the FLT T/N ratio was significantly larger than that of the MET T/N ratio (P < 0.01). The mean T/N ratio of FLT-PET/CT in IDH1-wildtype tumours was significantly higher than that in IDH1-mutant tumours among grade II and III gliomas (P = 0.005), but this was not the case for MET-PET/CT. Both MET-PET/CT and FLT-PET/CT were able to distinguish between grade II and III gliomas in IDH1-mutant tumours (P = 0.002 and P < 0.001, respectively), but only FLT-PET/CT was able to distinguish between grade III and IV gliomas in IDH1-wildtype tumours (P = 0.029). Conclusion This study showed that FLT-PET/CT can be used to determine the IDH1 mutation status and evaluate glioma grade more accurately than MET-PET/CT. FLT-PET/CT can improve glioma differentiation based on the 2016 WHO classification, but caution must be paid for tumours without contrast enhancement and further studies should be conducted with more cases.

The authors report on a case of concurrent herpes simplex encephalitis (HSE) and malignant glioma. The co-occurrence of HSE and malignant glioma is very rare, but it can occur during glioma treatment. Both radiotherapy and chemoradiation with temozolomide can induce viral reactivation, leading to HSE relapse. Careful observation for HSE is necessary when administering chemoradiation to patients with a history of HSE. Antiviral therapy for HSE must be initiated immediately, and the chemoradiation for glioma should be stopped; however, it is not clear what antitumor therapy is optimal when HSE co-occurs during the treatment of glioma.

Primitive polar spongioblastoma was first described by Russell and Cairns in 1947. However, the polar spongioblastoma pattern is often seen in many neuroepithelial tumors, and this category was deleted in the previous World Health Organization (WHO) classification. In 2010, Nagaishi et al. reported on a case involving a neuroepithelial tumor with the typical histological pattern of polar spongioblastoma and suggested that this tumor might not be suited to any of the neuroepithelial tumors in the current WHO classification. We report on an autopsy case involving an unclassified high-grade glioma with polar spongioblastoma pattern that was very similar to the case described by Nagaishi et al. A 44-year-old man who presented with a headache exhibited a tumor of the right frontal lobe on MRI. Histological diagnosis of the tumor obtained by gross total resection was high-grade glioma, which was composed of the parallel palisading of spindle tumor cells expressing GFAP, without microvascular proliferation (MVP) and necrosis. Conventional chemoradiotherapy was performed, but the case was complicated by cerebrospinal fluid (CSF) dissemination that resulted in multiple extraneural metastases through systemic diversionary CSF shunting. Finally, the patient died approximately 13 months after the initial treatment. Both the cerebral and Douglas pouch tumors that were obtained at autopsy were diagnosed as typical glioblastomas, and they were composed of the proliferation of atypical astrocytes with MVP and pseudopalisading necrosis without the formation of rhythmic palisading. Although the histological findings were different from that of the first operation, immunohistochemical and genetic profiles demonstrated almost the same results. This tumor was not classified as a typical glioblastoma by the initial findings, but it had the nature of a glioblastoma. These findings suggest that the tumor might be classified as a new subset of glioblastoma called glioblastoma with polar spongioblastoma pattern.

3'-Deoxy-3'-[(18)F]-fluorothymidine ([(18)F]-FLT), a marker of cellular proliferation, has been used in positron emission tomography (PET) examination of gliomas. The aim of this study was to investigate whether the uptake of [(18)F]-FLT in glioma correlates with messenger RNA (mRNA) levels of the equilibrative nucleoside transporter 1 (ENT1), microvascular density (assessed by CD34 immunohistochemistry), and the blood-brain barrier (BBB) breakdown. A total of 21 patients with newly diagnosed glioma were examined with [(18)F]-FLT PET. Tumor lesions were identified as areas of focally increased [(18)F]-FLT uptake, exceeding that of surrounding normal tissue. Dynamic analysis of [(18)F]-FLT PET revealed correlations between the phosphorylation rate constant k 3 and ENT1 expression; however there was no correlation between the kinetic parameters and CD34 score. There was a good correlation between the gadolinium (Gd) enhancement score (evaluating BBB breakdown) and ENT1 expression, CD34 score, and Ki-67 index. This preliminary study suggests that ENT1 expression might not reflect accumulation of [(18)F]-FLT in vivo due to BBB permeability in glioma.

The use of positron imaging agents such as FDG, MET, and FLT is expected to lead the way for novel applications toward efficient malignancy grading and treatment of gliomas. In this study, the usefulness of FDG, MET and FLT-PET images was retrospectively reviewed by comparing their histopathological findings. FDG, MET, and FLT-PET were performed in 27 patients with WHO grade IV, 15 patients with WHO grade III, and 12 patients with WHO grade II during 5.5 years. The resulting PET images were compared by measuring SUVs and T/N ratios (tumor to normal tissue ratios). Although there were no significant differences in FDG-PET, there were significant differences in the T/N ratios in the MET-PET between WHO grades II and IV and in the FLT-PET between the WHO grades III and IV. In glioblastoma patients, the SUVs of the areas depicted by MRI in the MET-PET were different from those SUVs in the FLT-PET. Importantly, the areas with high SUVs in both MET-PET and FLT-PET were also high in Ki-67 index and were histologically highly malignant. PET imaging is a noninvasive modality that is useful in determining a tumor area for removal as well as improving preoperative diagnosis for gliomas.

OBJECTIVE: Use of the positron imaging agents, such as 11C-Methionine (MET) and 18F-Fluoromisonidazole (FMISO), is expected to lead the way for novel applications aimed at achieving efficient malignancy grading and treatment of gliomas. The aim of this study was to assess MET and FMISO PET studies to evaluate the biological effects induced by bevacizumab therapy in patients treated for high grade gliomas. METHODS: Twenty-two patients with high grade gliomas were treated biweekly with bevacizumab from July 2013 to May 2015. MR images, as well as MET and FMISO PET scans were obtained at baseline and at follow-up (4 weeks after treatment onset). MRI treatment response was evaluated by T1/T2 volumetry according to the response assessment in neuro-oncology (RANO) criteria. Based on the RANO criteria, we divided the patients into three groups (PR, SD, and PD), and compared changes of MET T/N ratio or FMISO T/B ratio between baseline and follow-up. These PET response assessments were compared in relation to PFS and OS. RESULTS: At the follow-up, MRI showed PR in 6 of 22 patients, SD in 11 of 22 patients, and PD in 5 of 22 patients. The median PFS were 13.1 months, 13.5 months and 2.4 months for PR, SD and PD, respectively. The median OS were 14.6 months, 14.5 months and 5.7 months for each group. MET and FMISO images in the PD group had a tendency to show the increase of changes. FMISO images in the SD group revealed 3 of 11 increased changes (15.1% up) and 8 of 11 decreased changes (11% down). The median PFS were 2.4 months and 16.3 months for each change, and the median OS were 9.8 months and 16.8 months. CONCLUSION: Decreased changes in FMISO-PET after bevacizumab therapy may be a useful biomarker for predicting PFS and OS in high-grade gliomas.