Enhancing predictability of IDH mutation status in glioma patients at initial diagnosis: a comparative analysis of radiomics from MRI, [18F]FET PET, and TSPO PET

PURPOSE

According to the World Health Organization classification for tumors of the central nervous system, mutation status of the isocitrate dehydrogenase (IDH) genes has become a major diagnostic discriminator for gliomas. Therefore, imaging-based prediction of IDH mutation status is of high interest for individual patient management. We compared and evaluated the diagnostic value of radiomics derived from dual positron emission tomography (PET) and magnetic resonance imaging (MRI) data to predict the IDH mutation status non-invasively.

METHODS

Eighty-seven glioma patients at initial diagnosis who underwent PET targeting the translocator protein (TSPO) using [18F]GE-180, dynamic amino acid PET using [18F]FET, and T1-/T2-weighted MRI scans were examined. In addition to calculating tumor-to-background ratio (TBR) images for all modalities, parametric images quantifying dynamic [18F]FET PET information were generated. Radiomic features were extracted from TBR and parametric images. The area under the receiver operating characteristic curve (AUC) was employed to assess the performance of logistic regression (LR) classifiers. To report robust estimates, nested cross-validation with five folds and 50 repeats was applied.

RESULTS

TBRGE-180 features extracted from TSPO-positive volumes had the highest predictive power among TBR images (AUC 0.88, with age as co-factor 0.94). Dynamic [18F]FET PET reached a similarly high performance (0.94, with age 0.96). The highest LR coefficients in multimodal analyses included TBRGE-180 features, parameters from kinetic and early static [18F]FET PET images, age, and the features from TBRT2 images such as the kurtosis (0.97).

CONCLUSION

The findings suggest that incorporating TBRGE-180 features along with kinetic information from dynamic [18F]FET PET, kurtosis from TBRT2, and age can yield very high predictability of IDH mutation status, thus potentially improving early patient management.

Improved prognostic stratification of patients with isocitrate dehydrogenase-mutant astrocytoma

Prognostic factors and standards of care for astrocytoma, isocitrate dehydrogenase (IDH)-mutant, CNS WHO grade 4, remain poorly defined. Here we sought to explore disease characteristics, prognostic markers, and outcome in patients with this newly defined tumor type. We determined molecular biomarkers and assembled clinical and outcome data in patients with IDH-mutant astrocytomas confirmed by central pathology review. Patients were identified in the German Glioma Network cohort study; additional cohorts of patients with CNS WHO grade 4 tumors were identified retrospectively at two sites. In total, 258 patients with IDH-mutant astrocytomas (114 CNS WHO grade 2, 73 CNS WHO grade 3, 71 CNS WHO grade 4) were studied. The median age at diagnosis was similar for all grades. Karnofsky performance status at diagnosis inversely correlated with CNS WHO grade (p < 0.001). Despite more intensive treatment upfront with higher grade, CNS WHO grade was strongly prognostic: median overall survival was not reached for grade 2 (median follow-up 10.4 years), 8.1 years (95% CI 5.4-10.8) for grade 3, and 4.7 years (95% CI 3.4-6.0) for grade 4. Among patients with CNS WHO grade 4 astrocytoma, median overall survival was 5.5 years (95% CI 4.3-6.7) without (n = 58) versus 1.8 years (95% CI 0-4.1) with (n = 12) homozygous CDKN2A deletion. Lower levels of global DNA methylation as detected by LINE-1 methylation analysis were strongly associated with CNS WHO grade 4 (p < 0.001) and poor outcome. MGMT promoter methylation status was not prognostic for overall survival. Histomolecular stratification based on CNS WHO grade, LINE-1 methylation level, and CDKN2A status revealed four subgroups of patients with significantly different outcomes. In conclusion, CNS WHO grade, global DNA methylation status, and CDKN2A homozygous deletion are prognostic in patients with IDH-mutant astrocytoma. Combination of these parameters allows for improved prediction of outcome. These data aid in designing upcoming trials using IDH inhibitors.

Deciphering sources of PET signals in the tumor microenvironment of glioblastoma at cellular resolution

Various cellular sources hamper interpretation of positron emission tomography (PET) biomarkers in the tumor microenvironment (TME). We developed an approach of immunomagnetic cell sorting after in vivo radiotracer injection (scRadiotracing) with three-dimensional (3D) histology to dissect the cellular allocation of PET signals in the TME. In mice with implanted glioblastoma, translocator protein (TSPO) radiotracer uptake per tumor cell was higher compared to tumor-associated microglia/macrophages (TAMs), validated by protein levels. Translation of in vitro scRadiotracing to patients with glioma immediately after tumor resection confirmed higher single-cell TSPO tracer uptake of tumor cells compared to immune cells. Across species, cellular radiotracer uptake explained the heterogeneity of individual TSPO-PET signals. In consideration of cellular tracer uptake and cell type abundance, tumor cells were the main contributor to TSPO enrichment in glioblastoma; however, proteomics identified potential PET targets highly specific for TAMs. Combining cellular tracer uptake measures with 3D histology facilitates precise allocation of PET signals and serves to validate emerging novel TAM-specific radioligands.

[18F]F-DED PET imaging of reactive astrogliosis in neurodegenerative diseases: preclinical proof of concept and first-in-human data

OBJECTIVES

Reactive gliosis is a common pathological hallmark of CNS pathology resulting from neurodegeneration and neuroinflammation. In this study we investigate the capability of a novel monoamine oxidase B (MAO-B) PET ligand to monitor reactive astrogliosis in a transgenic mouse model of Alzheimer`s disease (AD). Furthermore, we performed a pilot study in patients with a range of neurodegenerative and neuroinflammatory conditions.

METHODS

A cross-sectional cohort of 24 transgenic (PS2APP) and 25 wild-type mice (age range: 4.3-21.0 months) underwent 60 min dynamic [¹⁸F]fluorodeprenyl-D2 ([¹⁸F]F-DED), static 18 kDa translocator protein (TSPO, [¹⁸F]GE-180) and β-amyloid ([¹⁸F]florbetaben) PET imaging. Quantification was performed via image derived input function (IDIF, cardiac input), simplified non-invasive reference tissue modelling (SRTM2, DVR) and late-phase standardized uptake value ratios (SUVr). Immunohistochemical (IHC) analyses of glial fibrillary acidic protein (GFAP) and MAO-B were performed to validate PET imaging by gold standard assessments. Patients belonging to the Alzheimer's disease continuum (AD, n = 2), Parkinson's disease (PD, n = 2), multiple system atrophy (MSA, n = 2), autoimmune encephalitis (n = 1), oligodendroglioma (n = 1) and one healthy control underwent 60 min dynamic [¹⁸F]F-DED PET and the data were analyzed using equivalent quantification strategies.

RESULTS

We selected the cerebellum as a pseudo-reference region based on the immunohistochemical comparison of age-matched PS2APP and WT mice. Subsequent PET imaging revealed that PS2APP mice showed elevated hippocampal and thalamic [¹⁸F]F-DED DVR when compared to age-matched WT mice at 5 months (thalamus: + 4.3%; p = 0.048), 13 months (hippocampus: + 7.6%, p = 0.022) and 19 months (hippocampus: + 12.3%, p < 0.0001; thalamus: + 15.2%, p < 0.0001). Specific [¹⁸F]F-DED DVR increases of PS2APP mice occurred earlier when compared to signal alterations in TSPO and β-amyloid PET and [¹⁸F]F-DED DVR correlated with quantitative immunohistochemistry (hippocampus: R = 0.720, p < 0.001; thalamus: R = 0.727, p = 0.002). Preliminary experience in patients showed [¹⁸F]F-DED V_T and SUVr patterns, matching the expected topology of reactive astrogliosis in neurodegenerative (MSA) and neuroinflammatory conditions, whereas the patient with oligodendroglioma and the healthy control indicated [¹⁸F]F-DED binding following the known physiological MAO-B expression in brain.

CONCLUSIONS

[¹⁸F]F-DED PET imaging is a promising approach to assess reactive astrogliosis in AD mouse models and patients with neurological diseases.

18 kDa translocator protein positron emission tomography facilitates early and robust tumor detection in the immunocompetent SB28 glioblastoma mouse model

INTRODUCTION

The 18 kDa translocator protein (TSPO) receives growing interest as a biomarker in glioblastoma. Mouse models can serve as an important tool for the investigation of biomarkers in glioblastoma, but several glioblastoma models indicated only low TSPO-PET signals in contrast to high TSPO-PET signals of human glioblastoma. Thus, we aimed to investigate TSPO-PET imaging in the syngeneic immunocompetent SB28 mouse model, which is thought to closely represent the tumor microenvironment (TME) of human glioblastoma.

METHODS

Dynamic TSPO-PET/CT imaging was performed for 60 min after injection of 13.6 ± 4.2 MBq [18F]GE-180. Contrast enhanced CT (ceCT) was acquired prior to PET and served for assessment of tumor volumes and attenuation correction. SB28 and sham mice were imaged at an early (week-1; n = 6 SB28, n = 6 sham) and a late time-point (week-3; n = 8 SB28, n = 9 sham) after inoculation. Standard of truth ex vivo tumor volumes were obtained for SB28 mice at the late time-point. Tracer kinetics were analyzed for the lesion site and the carotid arteries to establish an image derived input function (IDIF). TSPO-PET and ceCT lesion volumes were compared with ex vivo volumes by calculation of root-mean-square-errors (RMSE). Volumes of distribution (VTmax/mean) in the lesion were calculated using carotid IDIF and standardized uptake values (SUVmax/mean) were obtained for a 40-60 min time frame.

RESULTS

Higher uptake rate constants (K1) were observed for week-1 SB28 tumor lesions when compared to week-3 SB28 tumor lesions. Highest agreement between TSPO-PET lesion volumes and ex vivo tumor volumes was achieved with a 50% maximum threshold (RMSE-VT: 39.7%; RMSE-SUV: 34.4%), similar to the agreement of ceCT tumor volumes (RMSE: 30.1%). Lesions of SB28 mice had higher PET signal when compared to sham mice at week-1 (VTmax 6.6 ± 2.9 vs. 3.9 ± 0.8, p = 0.035; SUVmax 2.3 ± 0.5 vs. 1.2 ± 0.1, p < 0.001) and PET signals remained at a similar level at week-3 (VTmax 5.0 ± 1.6 vs. 2.7 ± 0.8, p = 0.029; SUVmax 1.9 ± 0.5 vs. 1.2 ± 0.2, p = 0.0012). VTmax correlated with SUVmax (R 2 = 0.532, p < 0.001).

CONCLUSION

TSPO-PET imaging of immunocompetent SB28 mice facilitates early detection of tumor signals over sham lesions. SB28 tumors mirror high TSPO-PET signals of human glioblastoma and could serve as a valuable translational model to study TSPO as an imaging biomarker.

P17.19.B Incidence of treatment-associated imaging changes in newly diagnosed MGMT promoter-methylated glioblastoma treated with cilengitide (EORTC 26071 - CENTRIC study): interim analysis

Background

In patients with glioblastoma, radiological recurrence of enhancing tissue after chemoradiotherapy can originate from progressive disease (PD) or from pseudoprogression/treatment-associated changes. There are no widely approved consensus criteria for treatment-associated changes. In the randomised EORTC-CENTRIC study (NCT00689221), patients with MGMT promoter-methylated glioblastoma were treated with chemoradiotherapy or chemoradiotherapy with cilengitide, an integrin inhibitor. We assessed the rate of treatment-associated changes in these groups according to the modified response assessment in neuro-oncology (RANO) criteria of 2017.

Methods

CENTRIC patients from both study arms with ≥3 follow-up MRIs were included. Preliminary PD (PPD) was defined as a ≥25% increase of the sum of perpendicular diameter (SPD) of a new or increasing lesion compared to baseline or nadir on the T1-MRI with gadolinium. Subsequent PD was defined as a second ≥25% increase of the SPD, at least 4 weeks later, or as a new lesion outside the radiation field. Treatment-associated changes were defined as stabilisation on ≥2 follow-up MRIs after PPD, each one 4 weeks later, or partial/complete regression on ≥1 follow-up MRI 4 weeks later.

Results

In total, 4,051 MRIs from 584 patients were available. This interim analysis included data on 462 patients with similar proportions in the cilengitide and control arm (50.9% and 49.1%). Due to missing MRIs or values, 128 were excluded. Of the remaining 334 patients, 157 (47%) patients showed RANO measurable disease at baseline or nadir (median SPD, 0mm2; interquartile range (IQR) 552.1 (0-552.1). After chemoradiotherapy with or without cilengitide, PPD occurred in 214 patients (64.1%) after a median time of 6.08 months after finishing radiation (IQR 11.4 (2.4-13.8), and 3.65 months after baseline or nadir (IQR 6.4 (2.1-8.5). After follow-up of these 214 patients, treatment-associated changes were diagnosed in 62 (18.6%) and PD was diagnosed in 48 (14.4%). The remaining 104 (31.1%) patients had no further follow-up MRI after PPD, mostly because a clinical decision to call PD was made. In the cilengitide group of 178 patients, 37 (20.8%) patients developed treatment-associated changes, and 23 (12.9%) patients developed PD, whereas in the control group of 156 patients, 25 (16%) patients developed treatment-associated changes, and 25 (16%) patients PD.

Conclusion

With the modified RANO criteria, the rate of treatment-associated changes was low compared to previous studies in newly diagnosed MGMT promoter-methylated glioblastoma. This rate did not change with addition of cilengitide. RANO-recommended radiological follow-up was not always awaited, which reflects clinical practice. Full data will be presented.

Investigational PET tracers in neuro-oncology-What's on the horizon? A report of the PET/RANO group

Many studies in patients with brain tumors evaluating innovative PET tracers have been published in recent years, and the initial results are promising. Here, the Response Assessment in Neuro-Oncology (RANO) PET working group provides an overview of the literature on novel investigational PET tracers for brain tumor patients. Furthermore, newer indications of more established PET tracers for the evaluation of glucose metabolism, amino acid transport, hypoxia, cell proliferation, and others are also discussed. Based on the preliminary findings, these novel investigational PET tracers should be further evaluated considering their promising potential. In particular, novel PET probes for imaging of translocator protein and somatostatin receptor overexpression as well as for immune system reactions appear to be of additional clinical value for tumor delineation and therapy monitoring. Progress in developing these radiotracers may contribute to improving brain tumor diagnostics and advancing clinical translational research.

Prospective validation of a new imaging scorecard to assess leptomeningeal metastasis: A joint EORTC BTG and RANO effort

BACKGROUND

Validation of the 2016 RANO MRI scorecard for leptomeningeal metastasis failed for multiple reasons. Accordingly, this joint EORTC Brain Tumor Group and RANO effort sought to prospectively validate a revised MRI scorecard for response assessment in leptomeningeal metastasis.

METHODS

Coded paired cerebrospinal MRI of 20 patients with leptomeningeal metastases from solid cancers at baseline and follow-up after treatment and instructions for assessment were provided via the EORTC imaging platform. The Kappa coefficient was used to evaluate the interobserver pairwise agreement.

RESULTS

Thirty-five raters participated, including 9 neuroradiologists, 17 neurologists, 4 radiation oncologists, 3 neurosurgeons, and 2 medical oncologists. Among single leptomeningeal metastases-related imaging findings at baseline, the best median concordance was noted for hydrocephalus (Kappa = 0.63), and the worst median concordance for spinal linear enhancing disease (Kappa = 0.46). The median concordance of raters for the overall response assessment was moderate (Kappa = 0.44). Notably, the interobserver agreement for the presence of parenchymal brain metastases at baseline was fair (Kappa = 0.29) and virtually absent for their response to treatment. 394 of 700 ratings (20 patients x 35 raters, 56%) were fully completed. In 308 of 394 fully completed ratings (78%), the overall response assessment perfectly matched the summary interpretation of the single ratings as proposed in the scorecard instructions.

CONCLUSION

This study confirms the principle utility of the new scorecard, but also indicates the need for training of MRI assessment with a dedicated reviewer panel in clinical trials. Electronic case report forms with "blocking options" may be required to enforce completeness and quality of scoring.

Impact of TSPO Receptor Polymorphism on [18F]GE-180 Binding in Healthy Brain and Pseudo-Reference Regions of Neurooncological and Neurodegenerative Disorders

TSPO-PET tracers are sensitive to a single-nucleotide polymorphism (rs6971-SNP), resulting in low-, medium- and high-affinity binders (LABs, MABs and HABS), but the clinical relevance of [18F]GE-180 is still unclear. We evaluated the impact of rs6971-SNP on in vivo [18F]GE-180 binding in a healthy brain and in pseudo-reference tissue in neuro-oncological and neurodegenerative diseases. Standardized uptake values (SUVs) of [18F]GE-180-PET were assessed using a manually drawn region of interest in the frontoparietal and cerebellar hemispheres. The SUVs were compared between the LABs, MABs and HABs in control, glioma, four-repeat tauopathy (4RT) and Alzheimer's disease (AD) subjects. Second, the SUVs were compared between the patients and controls within their rs6971-subgroups. After excluding patients with prior therapy, 24 LABs (7 control, 5 glioma, 6 4RT and 6 AD) were analyzed. Age- and sex-matched MABs (n = 38) and HABs (n = 50) were selected. The LABs had lower frontoparietal and cerebellar SUVs when compared with the MABs and HABs, but no significant difference was observed between the MABs and HABs. Within each rs6971 group, no SUV difference between the patients and controls was detected in the pseudo-reference tissues. The rs6971-SNP affects [18F]GE-180 quantification, revealing lower binding in the LABs when compared to the MABs and HABs. The frontoparietal and cerebellar ROIs were successfully validated as pseudo-reference regions.

Advances in multidisciplinary therapy for meningiomas

Surgery has long been established as the first-line treatment for the majority of symptomatic and enlarging meningiomas, and evidence for its success is derived from retrospective case series. Despite surgical resection, a subset of meningiomas display aggressive behavior with early recurrences that are difficult to treat. The decision to radically resect meningiomas and involved structures is balanced against the risk for neurological injury in patients. Radiation therapy has largely been used as a complementary and safe therapeutic strategy in meningiomas with evidence primarily stemming from retrospective, single-institution reports. Two of the first cooperative group studies (RTOG 0539 and EORTC 22042) evaluating the outcomes of adjuvant radiation therapy in higher-risk meningiomas have shown promising preliminary results. Historically, systemic therapy has resulted in disappointing results in meningiomas. However, several clinical trials are under way evaluating the efficacy of chemotherapies, such as trabectedin, and novel molecular agents targeting Smoothened, AKT1, and focal adhesion kinase in patients with recurrent meningiomas.

OS2.2 Chemotherapy for spinal gliomas in adults

BACKGROUND

Chemotherapy is a treatment option in patients diagnosed with anaplastic gliomas or glioblastomas of the spinal cord, or with recurrent lower graded WHO spinal gliomas that are no longer amenable to local treatment. The low incidence of spinal cord gliomas, particularly in adults, limits the ability to perform clinical trials. The role of chemotherapy in these tumors has remained unclear.

MATERIAL AND METHODS

We performed a retrospective study of 22 patients diagnosed with spinal gliomas who were treated with chemotherapy at any time during the disease course. Benefit from chemotherapy was estimated by applying Response assessment in neuro-oncology criteria. Data on radiotherapy, as well as the number of neurosurgical interventions were taken into consideration.

RESULTS

Most patients were diagnosed with astrocytoma WHO grade I-IV (N=14), the remaining patients were diagnosed with ependymoma (N=8). Median follow-up from start of chemotherapy was 92 months (95% CI, 72.6–111.4). The O6-methylguanyl-DNA-methyltransferase(MGMT)promoter methylation status was available in tumors of 12 patients: 9 tumors (75%) had an unmethylated MGMTpromoter. More than 50% of the patients had more than one neurosurgical intervention. After prior surgery 10 patients in the first-line setting had chemotherapy combined with radiotherapy, while 3 patients received chemotherapy only. The remaining 9 patients had initially received radiation therapy and chemotherapy was given at time of recurrence. In patients diagnosed with astrocytoma mainly temozolomide (TMZ) was applied (N=10), while one patient received CCNU and three patients had combination chemotherapy. Patients diagnosed with ependymoma had hydroxyurea (N=1), CCNU (N=1), TMZ (N=3) or combination chemotherapy (N=3). In the group of patients who had chemotherapy combined with radiation, response rates were as follows: anaplastic astrocytoma 3 stable diseases (SD), glioblastoma 1 complete response (CR) and 1 SD, and anaplastic ependymoma 1 SD. After chemotherapy in the group of patients previously irradiated, the following response rates were observed: 1 SD in pilocytic astrocytoma, 1 SD in diffuse astrocytoma, 3 SD in myxopapillary ependymoma, and 2 SD and 1 partial response (PR) in anaplastic ependymoma. All other patients experienced progressive disease. There was no indication for a favorable prognostic role ofMGMTpromoter methylation.

CONCLUSION

Spinal cord gliomas represent a heterogeneous group of tumors. Survival outcomes in response to chemotherapy in adult spinal glioma patients vary substantially, but individual patients appear to derive benefit from chemotherapy.

TSPO PET, tumour grading and molecular genetics in histologically verified glioma: a correlative 18F-GE-180 PET study

BACKGROUND

The 18-kDa translocator protein (TSPO) is overexpressed in brain tumours and represents an interesting target for glioma imaging. ¹⁸F-GE-180, a novel TSPO ligand, has shown improved binding affinity and a high target-to-background contrast in patients with glioblastoma. However, the association of uptake characteristics on TSPO PET using ¹⁸F-GE-180 with the histological WHO grade and molecular genetic features so far remains unknown and was evaluated in the current study.

METHODS

Fifty-eight patients with histologically validated glioma at initial diagnosis or recurrence were included. All patients underwent ¹⁸F-GE-180 PET, and the maximal and mean tumour-to-background ratios (TBR_max, TBR_mean) as well as the PET volume were assessed. On MRI, presence/absence of contrast enhancement was evaluated. Imaging characteristics were correlated with neuropathological parameters (i.e. WHO grade, isocitrate dehydrogenase (IDH) mutation, O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation and telomerase reverse transcriptase (TERT) promoter mutation).

RESULTS

Six of 58 patients presented with WHO grade II, 16/58 grade III and 36/58 grade IV gliomas. An (IDH) mutation was found in 19/58 cases, and 39/58 were classified as IDH-wild type. High ¹⁸F-GE-180-uptake was observed in all but 4 cases (being WHO grade II glioma, IDH-mutant). A high association of ¹⁸F-GE-180-uptake and WHO grades was seen: WHO grade IV gliomas showed the highest uptake intensity compared with grades III and II gliomas (median TBR_max 5.15 (2.59-8.95) vs. 3.63 (1.85-7.64) vs. 1.63 (1.50-3.43), p < 0.001); this association with WHO grades persisted within the IDH-wild-type and IDH-mutant subgroup analyses (p < 0.05). Uptake intensity was also associated with the IDH mutational status with a trend towards higher ¹⁸F-GE-180-uptake in IDH-wild-type gliomas in the overall group (median TBR_max 4.67 (1.56-8.95) vs. 3.60 (1.50-7.64), p = 0.083); however, within each WHO grade, no differences were found (e.g. median TBR_max in WHO grade III glioma 4.05 (1.85-5.39) vs. 3.36 (2.32-7.64), p = 1.000). No association was found between uptake intensity and MGMT or TERT (p > 0.05 each).

CONCLUSION

Uptake characteristics on ¹⁸F-GE-180 PET are highly associated with the histological WHO grades, with the highest ¹⁸F-GE-180 uptake in WHO grade IV glioblastomas and a PET-positive rate of 100% among the investigated high-grade gliomas. Conversely, all TSPO-negative cases were WHO grade II gliomas. The observed association of ¹⁸F-GE-180 uptake and the IDH mutational status seems to be related to the high inter-correlation of the IDH mutational status and the WHO grades.

Biological tumour volumes of gliomas in early and standard 20-40 min 18F-FET PET images differ according to IDH mutation status

PURPOSE

For the clinical evaluation of O-(2-¹⁸F-fluoroethyl)-L-tyrosine (¹⁸F-FET) PET images, the use of standard summation images obtained 20-40 min after injection is recommended. However, early summation images obtained 5-15 min after injection have been reported to allow better differentiation between low-grade glioma (LGG) and high-grade glioma (HGG) by capturing the early ¹⁸F-FET uptake peak specific for HGG. We compared early and standard summation images with regard to delineation of the PET-derived biological tumour volume (BTV) in correlation with the molecular genetic profile according the updated 2016 WHO classification.

METHODS

The analysis included 245 patients with newly diagnosed, histologically verified glioma and a positive ¹⁸F-FET PET scan prior to any further treatment. BTVs were delineated during the early 5-15 min and standard 20-40 min time frames using a threshold of 1.6 × background activity and were compared intraindividually. Volume differences between early and late summation images of >20% were considered significant and were correlated with WHO grade and the molecular genetic profile (IDH mutation and 1p/19q codeletion status).

RESULTS

In 52.2% of the patients (128/245), a significant difference in BTV of >20% between early and standard summation images was found. While 44.3% of WHO grade II gliomas (31 of 70) showed a significantly smaller BTV in the early summation images, 35.0% of WHO grade III gliomas (28/80) and 37.9% of WHO grade IV gliomas (36/95) had a significantly larger BTVs. Among IDH-wildtype gliomas, an even higher portion (44.4%, 67/151) showed significantly larger BTVs in the early summation images, which was observed in 5.3% (5/94) of IDH-mutant gliomas only: most of the latter had significantly smaller BTVs in the early summation images, i.e. 51.2% of IDH-mutant gliomas without 1p/19q codeletion (21/41) and 39.6% with 1p/19q codeletion (21/53).

CONCLUSION

BTVs delineated in early and standard summation images differed significantly in more than half of gliomas. While the standard summation images seem appropriate for delineation of LGG as well as IDH-mutant gliomas, a remarkably high percentage of HGG and, particularly, IDH-wildtype gliomas were depicted with significantly larger volumes in early summation images. This finding might be of interest for optimization of treatment planning (e.g. radiotherapy) in accordance with the individual IDH mutation status.

Diagnosis and treatment of brain metastases from solid tumors: guidelines from the European Association of Neuro-Oncology (EANO)

The management of patients with brain metastases has become a major issue due to the increasing frequency and complexity of the diagnostic and therapeutic approaches. In 2014, the European Association of Neuro-Oncology (EANO) created a multidisciplinary Task Force to draw evidence-based guidelines for patients with brain metastases from solid tumors. Here, we present these guidelines, which provide a consensus review of evidence and recommendations for diagnosis by neuroimaging and neuropathology, staging, prognostic factors, and different treatment options. Specifically, we addressed options such as surgery, stereotactic radiosurgery/stereotactic fractionated radiotherapy, whole-brain radiotherapy, chemotherapy and targeted therapy (with particular attention to brain metastases from non-small cell lung cancer, melanoma and breast and renal cancer), and supportive care.

Response Assessment in Neuro-Oncology working group and European Association for Neuro-Oncology recommendations for the clinical use of PET imaging in gliomas

This guideline provides recommendations for the use of PET imaging in gliomas. The review examines established clinical benefit in glioma patients of PET using glucose ((18)F-FDG) and amino acid tracers ((11)C-MET, (18)F-FET, and (18)F-FDOPA). An increasing number of studies have been published on PET imaging in the setting of diagnosis, biopsy, and resection as well radiotherapy planning, treatment monitoring, and response assessment. Recommendations are based on evidence generated from studies which validated PET findings by histology or clinical course. This guideline emphasizes the clinical value of PET imaging with superiority of amino acid PET over glucose PET and provides a framework for the use of PET to assist in the management of patients with gliomas.

[Cognitive Function in Patients Before and After Micro-neurosurgical Resection of Frontal Brain Tumors]

Patients with lesions of the prefrontal cortex as a result of frontal brain tumors (intra- and extra-axial) can show impairments of executive functions 1 2 3 4. Although there are a large number of psychological tests, the detection of impairments of relevant everyday executive functions in these patients is still extremely difficult. In 30 patients with lesions of the prefrontal cortex, the executive functions were tested with the Behavioral Assessment of Dysexecutive Syndrome (BADS) and 21 patients were also followed up postoperatively. Additionally, if possible, the Wisconsin Card Sorting Test (WCST), a widely used executive function test, and the Wechsler Adult Intelligence Scale (WAIS) for general cognitive performance were conducted. Pre- and postoperatively, a total of 16 patients were followed up with all three tests. The aim was to investigate the neuropsychological assessment pre- and postoperatively, to evaluate it in terms of deficits and changes in performance and to ensure that no new relevant everyday cognitive deficits arose. Preoperatively, only one patient, who could not be tested post-surgery, showed a reduced overall profile value in the BADS.  In all tested patients, there was no evidence of deterioration of cognitive status 8 - 12 weeks postoperatively. Further investigations using fMRI should be used to clarify whether the results obtained should be interpreted as neuroplastic adaptations of prefrontal cognitive functions or as a failure to detect deficits due to a lack of sensitivity of the tests used.

Optimized surgical treatment for normal pressure hydrocephalus: comparison between gravitational and differential pressure valves

OBJECTIVES

In idiopathic normal pressure hydrocephalus (NPH) ventriculoperitoneal (VP) shunt insertion is the method of choice to improve cardinal symptoms such as gait disturbance, urge incontinence and/or dementia. With reduced compliance, the brain of the elderly is prone for overdrainage complications. This was especially true with the use of differential pressure valve implantation. The present study compares clinical outcome and complication rates after VP shunt insertion with differential pressure valves in the early years and gravitational valves since 2005.

METHODS

The authors reviewed patients treated at our institution for NPH since 1995. Differential pressure valves were solely used in the initial years, while the treatment regimen changed to gravitational valves in 2005. Clinical improvement/surgical success rates as well as complications were compared between the two groups.

RESULTS

Eighty-nine patients were enrolled for the present study. Mean age at the time of surgery was 73.5 ± 6.3 years. Male patients predominated with 73, compared with 16 female patients. Median follow-up time was 28 ± 26 months. Date of last follow-up was 1st October 2013. Forty-nine patients received a gravitational valve, while 40 were treated with differential pressure valves. In the gravitational group a significant improvement was observed after shunt insertion for gait disorder, cognitive impairment and urge incontinence (p < 0.0001, resp. p = 0.004), while a significant change in the differential pressure group was only seen for gait disorder (p = 0.03) but not for cognition or urinary incontinency (p > 0.05). The risk of hygroma as a sign of shunt overdrainage requiring surgical intervention was significantly higher in the differential pressure group (5 versus 0 in the gravitational group).

CONCLUSIONS

Patients with NPH treated with gravitational valves in the present cohort showed a more profound improvement in their initial symptoms, including gait disorder, cognitive impairment and urinary incontinency without the risk of overdrainage complications requiring surgical intervention when compared with patients who received differential pressure valves in previous years.

Personalized care in neuro-oncology coming of age: why we need MGMT and 1p/19q testing for malignant glioma patients in clinical practice

Histological subtyping and grading by malignancy are the cornerstones of the World Health Organization (WHO) classification of tumors of the central nervous system. They shall provide clinicians with guidance as to the course of disease to be expected and the choices of treatment to be made. Nonetheless, patients with histologically identical tumors may have very different outcomes, notably in patients with astrocytic and oligodendroglial gliomas of WHO grades II and III. In gliomas of adulthood, 3 molecular markers have undergone extensive studies in recent years: 1p/19q chromosomal codeletion, O(6)-methylguanine methyltransferase (MGMT) promoter methylation, and mutations of isocitrate dehydrogenase (IDH) 1 and 2. However, the assessment of these molecular markers has so far not been implemented in clinical routine because of the lack of therapeutic implications. In fact, these markers were considered to be prognostic irrespective of whether patients were receiving radiotherapy (RT), chemotherapy, or both (1p/19q, IDH1/2), or of limited value because testing is too complex and no chemotherapy alternative to temozolomide was available (MGMT). In 2012, this situation has changed: long-term follow-up of the Radiation Therapy Oncology Group 9402 and European Organisation for Research and Treatment of Cancer 26951 trials demonstrated an overall survival benefit from the addition to RT of chemotherapy with procarbazine/CCNU/vincristine confined to patients with anaplastic oligodendroglial tumors with (vs without) 1p/19q codeletion. Furthermore, in elderly glioblastoma patients, the NOA-08 and the Nordic trial of RT alone versus temozolomide alone demonstrated a profound impact of MGMT promoter methylation on outcome by therapy and thus established MGMT as a predictive biomarker in this patient population. These recent results call for the routine implementation of 1p/19q and MGMT testing at least in subpopulations of malignant glioma patients and represent an encouraging step toward the development of personalized therapeutic approaches in neuro-oncology.

Varicella zoster virus infection of malignant glioma cell cultures: a new candidate for oncolytic virotherapy?

BACKGROUND

Glioblastoma multiforme is a highly aggressive tumor with a median survival of 14 months despite all standard therapies. Focusing on alternative treatment strategies, we evaluated the oncolytic potential of varicella zoster virus (VZV) in malignant glioma cell cultures.

MATERIALS AND METHODS

Replication of wildtype and mutant VZV was comparatively analyzed in glioma cell lines (U87, U251 and U373) and in primary malignant glioma cells (n=10) in vitro by infectious foci assay, immunofluorescence microscopy and western blot analysis. Additionally, the tumor-targeting potential of VZV-infected human mesenchymal stem cells was evaluated.

RESULTS

VZV replicated efficiently in all the glioma cells studied here followed by rapid oncolysis in vitro. The attenuated vaccine VZV mutant rOKA/ORF63rev[T171] exhibited most efficient replication. Human mesenchymal stem cells were found suitable for targeting VZV to sites of tumor growth.

CONCLUSION

VZV exhibits an intrinsic oncolytic potential in malignant glioma cell cultures and might be a novel candidate for virotherapy in glioblastoma multiforme.

O-methylguanine-DNA methyltransferase (MGMT) mRNA expression predicts outcome in malignant glioma independent of MGMT promoter methylation

BACKGROUND

We analyzed prospectively whether MGMT (O(6)-methylguanine-DNA methyltransferase) mRNA expression gains prognostic/predictive impact independent of MGMT promoter methylation in malignant glioma patients undergoing radiotherapy with concomitant and adjuvant temozolomide or temozolomide alone. As DNA-methyltransferases (DNMTs) are the enzymes responsible for setting up and maintaining DNA methylation patterns in eukaryotic cells, we analyzed further, whether MGMT promoter methylation is associated with upregulation of DNMT expression.

METHODOLOGY/PRINCIPAL FINDINGS

ADULT PATIENTS WITH A HISTOLOGICALLY PROVEN MALIGNANT ASTROCYTOMA (GLIOBLASTOMA: N = 53, anaplastic astrocytoma: N = 10) were included. MGMT promoter methylation was determined by methylation-specific PCR (MSP) and sequencing analysis. Expression of MGMT and DNMTs mRNA were analysed by real-time qPCR. Prognostic factors were obtained from proportional hazards models. Correlation between MGMT mRNA expression and MGMT methylation status was validated using data from the Cancer Genome Atlas (TCGA) database (N = 229 glioblastomas). Low MGMT mRNA expression was strongly predictive for prolonged time to progression, treatment response, and length of survival in univariate and multivariate models (p<0.0001); the degree of MGMT mRNA expression was highly correlated with the MGMT promoter methylation status (p<0.0001); however, discordant findings were seen in 12 glioblastoma patients: Patients with methylated tumors with high MGMT mRNA expression (N = 6) did significantly worse than those with low transcriptional activity (p<0.01). Conversely, unmethylated tumors with low MGMT mRNA expression (N = 6) did better than their counterparts. A nearly identical frequency of concordant and discordant findings was obtained by analyzing the TCGA database (p<0.0001). Expression of DNMT1 and DNMT3b was strongly upregulated in tumor tissue, but not correlated with MGMT promoter methylation and MGMT mRNA expression.

CONCLUSIONS/SIGNIFICANCE

MGMT mRNA expression plays a direct role for mediating tumor sensitivity to alkylating agents. Discordant findings indicate methylation-independent pathways of MGMT expression regulation. DNMT1 and DNMT3b are likely to be involved in CGI methylation. However, their exact role yet has to be defined.

Hot spots in dynamic (18)FET-PET delineate malignant tumor parts within suspected WHO grade II gliomas

Molecular imaging studies have recently found inter- and intratumoral heterogeneity in World Health Organization (WHO) grade II gliomas. A correlative analysis with tumor histology, however, is still lacking. For elucidation we conducted the current prospective study. Fifty-five adult patients with an MRI-based suspicion of a WHO grade II glioma were included. [F-18]Fluoroethyltyrosine ((18)FET) uptake kinetic studies were combined with frame-based stereotactic localization techniques and used as a guide for stepwise (1-mm steps) histopathological evaluation throughout the tumor space. In tumors with heterogeneous PET findings, the O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status and expression of mutated protein isocitrate dehydrogenase variant R132H (IDH1) were determined inside and outside of hot spot volumes. Metabolic imaging revealed 3 subgroups: the homogeneous WHO grade II glioma group (30 patients), the homogeneous malignant glioma group (10 patients), and the heterogeneous group exhibiting both low- and high-grade characteristics at different sites (15 patients). Stepwise evaluation of 373 biopsy samples indicated a strong correlation with analyses of uptake kinetics (p < 0.0001). A homogeneous pattern of uptake kinetics was linked to homogeneous histopathological findings, whereas a heterogeneous pattern was associated with histopathological heterogeneity; hot spots exhibiting malignant glioma characteristics covered 4-44% of the entire tumor volumes. Both MGMT and IDH1 status were identical at different tumor sites and not influenced by heterogeneity. Maps of (18)FET uptake kinetics strongly correlated with histopathology in suspected grade II gliomas. Anaplastic foci can be accurately identified, and this finding has implications for prognostic evaluation and treatment planning.

Complementary therapy use in patients with glioma: an observational study

OBJECTIVE

Despite novel multimodal therapeutic approaches, the vast majority of glial tumors are not curable. Patients may search for complementary therapies in order to contribute to the fight against their disease or to relieve symptoms induced by their brain tumor. The extent of the use of complementary or alternative therapies, the patients' rationale behind it, and the cost of complementary therapy for gliomas are not known. We used a questionnaire and the database of the German Glioma Network to evaluate these questions.

METHODS

A total of 621 questionnaires were available for evaluation from patients with glial tumors of WHO grades II to grade IV. The patients were recruited from 6 neuro-oncologic centers in Germany. Complementary therapy was defined as methods or compounds not used in routine clinical practice and not scientifically evaluated.

RESULTS

Forty percent of the responding patients reported the use of complementary therapies. Significant differences between the group of complementary therapy users and nonusers were seen with respect to age (younger > older), gender (female > male), and education (high education level > low education level). The motivation for complementary therapy use was not driven by unsatisfactory clinical care by the neuro-oncologists, but by the wish to add something beneficial to the standard of care.

CONCLUSIONS

In clinical practice, patients' use of complementary therapies may be largely overseen and underestimated. The major motivation is not distrust in conventional therapies. Neuro-oncologists should be aware of this phenomenon and encourage an open but critical dialogue with their patients.

[Angiographic moyamoya in a female with glycogenosis type IA - a case report focusing therapeutic management: bilateral encephalo-duro-arterio-myo-synangiosis (EDAMS)]

Angiographic Moyamoya is a rare cerebrovascular disease most frequent in asia. Its characateristics are recurrent ischemic attacks due to progressive occlusion of ICA branches. Angiography reveals fine arterial collateralisation reminding of ascending smoke ("moyamoya" in japanese). Neurosurgical treatment strategies include direct and indirect reanastomosation procedures. Randomised trials for comparison of clinical outcome and long term survival remain missing. A 23 years old female with glycogenosis type IA was first diagnosed bilateral angiographic moyamoya with bilateral proximal stenosis of ICA after transient ischemic attack (TIA). Coincidence of both rare diseases moyamoya and glycogenosis has previously been reported in three cases, so that this metabolic dysfunction presumably is a true risk factor for moyamoya. In our case, excellent angiographic and functional results were achieved by bilateral, consecutive Enzephalo-Duro-Arterio-Myo-Synangiosis (EDAMS).

A Transmedullary Approach to Occlusion of a Ventral Perimedullary Arteriovenous Fistula of the Thoracic Spinal Cord

OBJECTIVE

A spinal perimedullary arteriovenous fistula (PMAVF) is a direct fistula of one or more spinal arteries into the perimedullary venous network with reversed venous flow and subsequent venous congestion of the spinal cord. The therapeutic goal of surgery is to normalize the venous drainage by obliterating the fistula. Strictly ventral lesions typically require an anterior approach to ensure adequate exposure of the fistula as well and the preservation of the physiological blood supply to the spinal cord.

CLINICAL PRESENTATION

We present a case of a ventral PMAVF at the level of T10 with feeders from the anterior spinal artery, caudally draining veins on the ventral spinal cord, and a dilated transmedullary vein filling cranially draining veins on the dorsal aspect of the spinal cord.

TECHNIQUE

The dilated transmedullary vein was approached by a laminectomy. The vein was coagulated, and the gliotic channel was used to approach the ventral fistula site from the dorsal surface of the spinal cord. Complete obliteration of the fistula was achieved, and the preoperative neurological deficit improved.

CONCLUSION

We conclude that transmedullarly draining veins offers a possible dorsal approach for the occlusion of some ventral PMAVFs, thus avoiding more complex anterior approaches to the ventral spinal cord.

Morphometric studies of the ligamentum flavum: a correlative microanatomical and MRI study of the lumbar spine

BACKGROUND

Foraminal degenerative lumbar stenosis is traditionally considered a result of bony narrowing due to osteophytic appositions on the superior articular process. Clinical experience reveals that significant additional compression of the neural structures is due to degenerative hypertrophy of the adjacent ligamentum flavum. Therefore, microanatomical and neuroradiological investigations were performed to determine the microtopography of this ligament, especially with respect to its lateral extension.

METHODS

Lumbar spine specimens of eight mid-aged human cadavers (mean age 34.5 years) were collected, and MRI studies with T1-weighted images were performed. The specially embedded specimens were sectioned horizontally at the level of the spinal ganglion (slice thickness: 2 mm). Anatomical morphometric data were correlated with identical measurements based on neuroradiological imaging and were analyzed statistically.

RESULTS

The distance between midline and extraforaminal extension of the ligamentum flavum showed a mean value of 17 mm. The distance increased to 19 mm when the lateral insertion was correlated to the origin of the ligamentum flavum at the anterior margin of the lamina. The farthest lateral segment of the ligamentum flavum was determined in each case; it covered the synovial cavity of the lumbar facet joint in the direction of the extraforaminal segment of the intervertebral canal.

CONCLUSIONS

Measurements from mid-aged cadavers show the extent of the ligamentum flavum including its intra- and extraforaminal parts. Due to this anatomical situation a hypertrophic ligamentum flavum may contribute significantly to nerve root compression at the level of the lateral spinal recess. This has to be kept in mind during surgical decompression, which might be incomplete unless these hypertrophied parts are completely removed.

[The facet syndrome: frequent cause of chronic backaches]

The lumbar facet syndrome (LFS) is a frequent cause of chronic backaches. A reliable diagnosis can be made through repeated facet blockades.The diagnosis is considered confirmed if the pain is significantly reduced over several hours. In addition to oral pain medication and physical measures, alternative minimally invasive therapeutic possibilities include surgical stabilization, as well as facet joint denervation. Both can be performed as thermodenervation or cryotherapy.

Interstitial iodine-125 radiosurgery alone or in combination with microsurgery for pediatric patients with eloquently located low-grade glioma: a pilot study

PURPOSE

The optimal therapeutic management of children with World Health Organization grade I and II gliomas not accessible to complete resection is poorly defined. Radical surgical resection is the first-line treatment for large hemispheric tumors, whereas interstitial iodine-125 radiosurgery (IRS) might be an attractive treatment concept for selected patients with small (tumor diameter in the range of 4 cm) and circumscribed tumors in any location of the brain. Precise high-dose application, maximal sparing of surrounding normal tissue, and the absence of long-term complications have been reported to be the hallmark of IRS. Therefore, the therapeutic impact and the risk of IRS alone or in combination with microsurgery (in case of larger tumor volumes) were prospectively examined.

METHODS

Seven boys and four girls were included (mean age, 6.8 years; range, 11 months to 16 years). IRS (after stereotactic biopsy) was considered to be indicated for circumscribed tumors with a diameter in the range of 4 cm (four cases). For larger tumors, a combined microsurgical/radiosurgical approach was preferred (seven patients). Temporary iodine-125 seeds were used exclusively (tumor dose calculated to the boundary, 54 Gy; dose rate, 10 cGy/h). Tumor location was hypothalamic/suprasellar in four, lobar in three, deep (thalamus and pineal gland) in two, and within the brain stem in two children. Treatment effects of IRS were estimated according to the MacDonald criteria.

RESULTS

A complete response after IRS was seen in four patients, and a partial response was seen in seven patients (median follow-up, 31.5 months). There was no perioperative morbidity after microsurgery and/or IRS, and no radiogenic complications occurred during the follow-up period. Five patients experienced an improvement in their deficits, and no deterioration in neurological/endocrine function was seen in any of the patients at the time of last follow-up evaluation.

CONCLUSION

IRS alone or in combination with microsurgery (in the case of larger tumors) is a safe, effective, and minimally invasive treatment strategy for eloquently located pediatric low-grade gliomas and deserves further prospective evaluation.

[Surgical treatment of cervical spinal canal stenosis in elderly patients]

The diagnosis is established through neurological examinations, laboratory and imaging diagnostics. Conservative treatment such as a neck brace, drug and physical therapies could bring relief. Manifest or progressing deficiency symptoms associated with sensory or motoric deficit, bladder, rectal or erectile disorder are indications for early surgery.

[Surgical treatment of lumbar spinal canal stenosis in elderly patients]

Lumbar spinal stenosis is one of the most frequent causes of spinal surgical interventions in over 60-year olds. The exact relationship between degenerative changes and the resulting symptoms is unclear since imaging shows stenotic changes in the spines of many symptom-free patients. The concurrence of imaging findings, the symptoms described and manifestations is crucial for the indication of surgical decompression. Nevertheless, spinal claudication that is refractory to conservative therapy is the most frequent indication for surgery. The success rate two years after OP is approximately 80% in over 75-year olds. Five years after surgical intervention, an improvement in the symptoms is still recognizable in 50% of these patients.

Serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma

Purpose

Intracavitary radioimmunotherapy (RIT) offers an effective adjuvant therapeutic approach in patients with malignant gliomas. Since differentiation between recurrence and reactive changes following RIT has a critical impact on patient management, the aim of this study was to analyse the value of serial O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (FET) PET scans in monitoring the effects of this locoregional treatment.

Methods

Following conventional therapy, 24 glioma patients (5 WHO III, 19 WHO IV) underwent one to five RIT cycles with either ¹³¹I-labelled (n=19) or ¹⁸⁸Re-labelled (n=5) anti-tenascin antibodies. Patients were monitored with serial FET PET scans (2–12 scans). For semiquantitative evaluation, maximal tumoural uptake (TU_max) was evaluated and the ratio to background (BG) was calculated. Results of PET were correlated with histopathological findings (n=9) and long-term clinical follow-up for up to 87 months.

Results

In seven tumour-free patients, PET revealed slightly increasing but homogeneous FET uptake surrounding the resection cavity with a peak up to 18 months following RIT (TU_max/BG 2.07±0.25) but stable or decreasing values during further follow-up (last follow-up: TU_max/BG 1.63±0.22). Seventeen patients developed regrowth of residual tumour/tumour recurrence showing additional nodular FET uptake (TU_max/BG 2.79±0.53). A threshold value of 2.4 (TU_max/BG) allowed best differentiation between recurrence and reactive changes (sensitivity 82%, specificity 100%).

Conclusion

FET PET is a sensitive tool for monitoring the effects of locoregional RIT. Homogeneous, slightly increasing FET uptake around the tumour cavity with a peak up to 18 months after RIT, followed by stable or decreasing uptake, points to benign, therapy-related changes. In contrast, nodular uptake is a reliable indicator of recurrence.

O-(2-[18F]fluoroethyl)-L-tyrosine PET for monitoring the effects of convection-enhanced delivery of paclitaxel in patients with recurrent glioblastoma

PURPOSE

Convection-enhanced delivery (CED) of paclitaxel is a new locoregional approach for patients with recurrent glioblastoma. The aim of this study was to evaluate O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) in monitoring the effects of this type of direct drug delivery.

METHODS

Eight patients with recurrent glioblastoma underwent CED of paclitaxel, which was infused over stereotactically placed catheters into the tumour. FET PET and MRI were performed before and 4 weeks after therapy and then at 3-month intervals to document follow-up. For quantitative evaluation, SUV(max)(tumour)/SUV(mean)(background) ratios were calculated.

RESULTS

At baseline all tumours showed gadolinium enhancement and high FET uptake (SUV(max)/BG 3.2+/-0.8). Four weeks after CED, a statistically significant decrease in FET uptake was seen (SUV(max)/BG-17%; p<0.01). During follow-up, no recurrence was observed within the CED area. Two out of eight patients with extended tumours died 4 and 5 months after treatment, most probably from local complications. Temporarily stable disease with stable FET uptake was observed in six of eight patients; this was followed by progression and increasing FET uptake ratios (+46%) distant from the CED area in five of the six patients 3-13 months after CED. One patient still presents stable FET uptake 10 months after CED. MRI showed unchanged/increasing contrast enhancement and oedema without ability to reliably assess disease progression.

CONCLUSION

FET PET is a valuable tool in monitoring the effects of CED of paclitaxel. In long-term follow-up, stable or decreasing FET uptake, even in contrast-enhancing lesions, is suggestive of reactive changes, whereas increasing ratios appear always to be indicative of recurrence. Therefore, FET PET is more reliable than MRI in differentiating stable disease from tumour regrowth.

Clinical quality standards for gamma knife radiosurgery--the Munich protocol

The clinical quality standards for outpatient gamma knife radiosurgery as developed in the German Gamma Knife Center Munich during the last ten years are described. The following aspects have been taken into account: appropriate patient selection, standardised treatment cycle, acquisition of high-quality stereotactic MR images, the integrated therapeutic concept, dose conformity and dose level, patient follow-up, quality control and scientific data analysis. Particular emphasis has been put on the importance of the interdisciplinary treatment concept by subspecialised experts. The results of the Munich concept in consideration of the described quality standards verifies that gamma knife radiosurgery is a safe and effective treatment option for well selected indications.

Mechanisms of glioma cell invasion

Invasive growth is one of the characteristics of gliomas--local infiltration into the surrounding nerve tissue decisively restricts all treatment strategies. Particularly the merit of all local treatment modalities is queried. The question whether a glioma represents a diffuse disease of the CNS or a local disturbance with unrestrained expansion tendency is still at issue. Understanding of the invasion mechanisms is of importance inasmuch as biologically reasonable and effective strategies of limiting and suppressing glioma invasion can only hence be derived. The affinity of glioma cells towards certain structures of the extracellular matrix as well as taking advantage of tumour vascularisation with regard to extension play a decisive role. Still not fully understood are tumour host interactions. Future thinking will have to take into account these interactions as well as evidence to be derived from development neurobiology and regeneration capacity of the CNS. The present review is meant to give a short overview and disclose many questions.

Microneurosurgery and radiosurgery--an attractive combination

Microneurosurgery and radiosurgery have made tremendous progress in terms of increasing efficacy and reducing treatment related mobility. Both techniques have clear indications; however, there is still competition between the two modalities in a variety of diseases. In all instances, this rivalry should be replaced by the concept of using both methods as complementary. Skull base tumours, metastases as well as certain AVMs are good candidates for this approach.