Local Intracerebral Immunomodulation Using Interleukin-Expressing Mesenchymal Stem Cells in Glioblastoma

PURPOSE

Mesenchymal stem cells (MSCs) show an inherent brain tumor tropism that can be exploited for targeted delivery of therapeutic genes to invasive glioma. We assessed whether a motile MSC-based local immunomodulation is able to overcome the immunosuppressive glioblastoma microenvironment and to induce an antitumor immune response.

EXPERIMENTAL DESIGN

We genetically modified MSCs to coexpress high levels of IL12 and IL7 (MSC^IL7/12, Apceth-301). Therapeutic efficacy was assessed in two immunocompetent orthotopic C57BL/6 glioma models using GL261 and CT2A. Immunomodulatory effects were assessed by multicolor flow cytometry to profile immune activation and exhaustion of tumor-infiltrating immune cells. Diversity of the tumor-specific immune response as analyzed using T-cell receptor sequencing.

RESULTS

Intratumoral administration of MSC^IL7/12 induced significant tumor growth inhibition and remission of established intracranial tumors, as demonstrated by MR imaging. Notably, up to 50% of treated mice survived long-term. Rechallenging of survivors confirmed long-lasting tumor immunity. Local treatment with MSC^IL7/12 was well tolerated and led to a significant inversion of the CD4⁺/CD8⁺ T-cell ratio with an intricate, predominantly CD8⁺ effector T-cell-mediated antitumor response. T-cell receptor sequencing demonstrated an increased diversity of TILs in MSC^IL7/12-treated mice, indicating a broader tumor-specific immune response with subsequent oligoclonal specification during generation of long-term immunity.

CONCLUSIONS

Local MSC-based immunomodulation is able to efficiently alter the immunosuppressive microenvironment in glioblastoma. The long-lasting therapeutic effects warrant a rapid clinical translation of this concept and have led to planning of a phase I/II study of apceth-301 in recurrent glioblastoma.

Quantitative Sensory Changes Following Gasserian Ganglion Radiofrequency Thermocoagulation in Patients with Medical Refractory Trigeminal Neuralgia: A Prospective Consecutive Case Series

BACKGROUND AND OBJECTIVE

 Microsurgical vascular nerve decompression and percutaneous ablative interventions aiming at the Gasserian ganglion are promising treatment modalities for patients with medical refractory trigeminal neuralgia (TN). Apart from clinical reports on a variable manifestation of facial hypoesthesia, the long-term impact of trigeminal ganglion radiofrequency thermocoagulation (RFT) on sensory characteristics has not yet been determined using quantitative methods.

MATERIAL AND METHODS

 We performed standardized quantitative sensory testing according to the established protocol of the German Research Network on Neuropathic Pain in a cohort of patients with classical (n = 5) and secondary (n = 11) TN before and after percutaneous Gasserian ganglion RFT (mean follow-up: 6 months). The test battery included thermal detection and thermal pain thresholds as well as mechanical detection and mechanical pain sensitivity measures. Clinical improvement was also assessed by means of renowned pain intensity and impairment questionnaires (Short-Form McGill Pain Questionnaire, Pain Disability Index, and Pain Catastrophizing Scale), pain numeric rating scale, and anti-neuropathic medication reduction at follow-up.

RESULTS

 All clinical parameters developed favorably following percutaneous thermocoagulation. Only mechanical and vibration detection thresholds of the affected side of the face were located below the reference frame of the norm population before and after the procedure. Statistically significant persistent changes in quantitative sensory variables caused by the intervention could not be detected in our patient sample.

CONCLUSION

 Our data suggest that TN patients improving considerably after RFT do not undergo substantial long-term alterations regarding quantitative sensory perception.

FOCAD loss impacts microtubule assembly, G2/M progression and patient survival in astrocytic gliomas

In search of novel genes associated with glioma pathogenesis, we have previously shown frequent deletions of the KIAA1797/FOCAD gene in malignant gliomas, and a tumor suppressor function of the encoded focadhesin impacting proliferation and migration of glioma cells in vitro and in vivo. Here, we examined an association of reduced FOCAD gene copy number with overall survival of patients with astrocytic gliomas, and addressed the molecular mechanisms that govern the suppressive effect of focadhesin on glioma growth. FOCAD loss was associated with inferior outcome in patients with isocitrate dehydrogenase 1 or 2 (IDH)-mutant astrocytic gliomas of WHO grades II-IV. Multivariate analysis considering age at diagnosis as well as IDH mutation, MGMT promoter methylation, and CDKN2A/B homozygous deletion status confirmed reduced FOCAD gene copy number as a prognostic factor for overall survival. Using a yeast two-hybrid screen and pull-down assays, tubulin beta-6 and other tubulin family members were identified as novel focadhesin-interacting partners. Tubulins and focadhesin co-localized to centrosomes where focadhesin was enriched in proximity to centrioles. Focadhesin was recruited to microtubules via its interaction partner SLAIN motif family member 2 and reduced microtubule assembly rates, possibly explaining the focadhesin-dependent decrease in cell migration. During the cell cycle, focadhesin levels peaked in G2/M phase and influenced time-dependent G2/M progression potentially via polo like kinase 1 phosphorylation, providing a possible explanation for focadhesin-dependent cell growth reduction. We conclude that FOCAD loss may promote biological aggressiveness and worsen clinical outcome of diffuse astrocytic gliomas by enhancing microtubule assembly and accelerating G2/M phase progression.

A Comparison between Pediatric and Adult Patients after Cranioplasty: Aseptic Bone Resorption Causes Earlier Revision in Children

BACKGROUND AND STUDY AIMS/OBJECTIVE

 Cranioplasty, a common neurosurgical intervention following decompressive craniectomy (DC), is associated with high complication rates. Bone flap resorption in particular leads to a considerable number of patients requiring further surgery. The aim of this study was to investigate the frequency and time of occurrence of complications following cranioplastic procedures in children and adults.

MATERIAL AND METHODS

 Data of children and adults who underwent cranioplasty between July 2010 and March 2018 were analyzed retrospectively. Clinical data, complications, and risk factors regarding aseptic bone resorption (ABR) were evaluated including patient age, occurrence of shunt-dependent hydrocephalus, and number of fragments in autologous bone flaps.

RESULTS

 Severe traumatic brain injury (TBI) was the leading cause for DC among children (66.7%), associated with a significantly higher number of fragments (p = 0.002). In the adult population, the most common cause was malignant infarction (55.9%) followed by TBI (24.6%). Pediatric patients in our institution received autologous bone flaps less frequently than adult patients (61.1% and 83.1%, respectively). Young age and a higher number of fragments in autologous bone flaps were associated with the occurrence of ABR. Children and adolescents showed significantly higher rates of aseptic bone necrosis (p = 0.007) and revision cranioplasty (p = 0.036). Kaplan-Meier estimates were used to further analyze bone flap resorption in children and adults, showing that revision surgery due to ABR was performed earlier in children (p = 0.001, log-rank test).

CONCLUSION

 Pediatric patients demand specific care when cranioplasty is performed following DC. We identified age as an independent risk factor. The higher number of fragments appears to be a correlation due to the higher number of TBIs in children. Our data indicate that young age is the most important risk factor for the development of ABR as a frequent and early complication with a shorter revision-free time interval in children. Consequently, the uncritical use of cryopreserved autologous bone flaps should be questioned in this population.

RARE-26. WHOLE GENOME SEQUENCING OF AN OSSEOUS METASTASIS DURING CHECKPOINT-CONTROLLED INTRACRANIAL GLIOBLASTOMA REVEALS NEW INSIGHTS INTO POTENTIAL MECHANISMS OF IMMUNE ESCAPE

Glioblastoma (GBM) has a devastating prognosis and recent advances in the treatment of a variety of cancer entities, e.g. through checkpoint inhibition, could so far not be translated into improved outcome in newly-diagnosed GBM. Characterizing rare cases of peripheral metastases which succeeded in overcoming immune control, can help to understand the mechanisms of immune escape. Here we describe the first reported case of a detailed genetic and immunological characterization of a peripheral bone metastasis from a GBM which was controlled intracranially by anti-PD1 checkpoint inhibition We performed whole genome sequencing (WGS) of the primary- and recurrent tumor, as well as the bone metastasis. Genomic data was analyzed for copy number variations and mutational profiles. In addition, immune monitoring with flow cytometric phenotyping and next-generation sequencing of the peripheral T-cell repertoire was used. A 70-year old patient developed multiple osseous metastases in the spine, while his IDHwt GBM recurrence was immunologically controlled with checkpoint inhibition. Biopsy confirmed peripheral GBM metastases. Immunophenotyping reflected the effective activation of the peripheral T-cell response, with, however, simultaneous upregulation of regulatory T-cells during disease progression. WGS sequencing demonstrated a distinct molecular profile of the GBM metastasis, with amplifications in chromosome 3 and 9, as well as genomic loss on chromosomes 4, 10 and 11. The peripheral metastasis was distinguished by mutations in mismatch repair genes, such as MSH4 and MLH1, associated with a hypermutated phenotype. Among the mutated genes we found potential candidates involved in immune escape of circulating tumor cells. This case represents a unique opportunity to analyze potential mechanisms of GBM-mediated immune escape during immune activation with anti-PD1 checkpoint therapy. It highlights the fact, that although an effective, disinhibited immune response can control the cranial GBM disease, hypermutated tumor clones can evade the tumor-specific T-cell response and disseminate to distant organs.

CSIG-11. CENTRAL NERVOUS SYSTEM TUMOR PATIENTS HAVE ELEVATED LEVELS OF CIRCULATING EXTRACELLULAR VESICLES

BACKGROUND

We previously demonstrated that extracellular vesicles (EV) from CNS tumors reflect the molecular subtype of the original tumor and mediate an exchange of pro-oncogenic signals. EVs are commonly characterized by nanoparticle analysis (NTA), electron microscopy and tetraspanin markers, including CD9, CD81 and CD63. It is unclear, however, to what extent circulating tumor EVs are utilizable for diagnostic purposes and how their marker profile overlaps with EVs derived from other cell types. Aiming to define markers that allow distinction and enrichment of glioma EVs from patient blood, we utilized Imaging Flow Cytometry (IFC) to discriminate single EVs via multiple surface markers.

METHODS

EVs were isolated from blood of patients suffering from glioblastoma (n=24), anaplastic astrocytoma (n=8), brain metastasis (n=7), meningioma (n=12), pituitary gland tumor (n=11), epilepsy (n=11) and from healthy controls (n=18) and were analyzed by IFC, immunoblotting, electron microscopy and NTA. In addition, circulating EVs from PALM-GFP-GL261 and PALM-GFP-CT2A tumor-bearing mice (n=5) as well as from glioblastoma stem-like (GSC) cultures (n=4), neural stem cells (NSC), cerebral endothelial cells (cEC) and T-cells (n=4) were characterized.

RESULTS

CNS tumor patients have significantly elevated levels of circulating EVs (P < 0.001), as measured by NTA and IFC. In particular, the proportion of double positive CD9+/CD81+, CD9+/CD63+and CD63+/CD81+EVs is increased in glioblastoma patients (p=0.018) compared with healthy controls[L1]. In accordance, cultured GSCs secrete increased levels of CD9+/CD81+EVs in vitro. In the two syngeneic murine PALM-GFP glioma models, only 0.1-0.01% of circulating plasma EVs were found to be derived from intracranial tumors, underlining the need to identify markers that can enrich tumor-specific EVs for molecular profiling.

CONCLUSION

Glioma patients display increased levels of circulating plasma EVs that can be profiled by IFC, which is a unique and novel technique that facilitates discrimination of different EV subpopulations.

CSIG-09. PROTEOMIC ANALYSIS OF MENINGIOMA CELL-DERIVED EXTRACELLULAR VESICLES: FIRST OF A KIND

BACKGROUND

Extracellular vesicles (EVs) play an important role in cell-cell communication in different types of tumors, carrying multiple layers of biological functional molecules, including proteins, RNA, DNA and lipids. Their implication as biomarkers in tumor disease is under current investigation. We previously showed that EVs in glioblastoma reflect the tumor subtype and that glioblastoma patients have elevated circulating particle counts. Regarding to meningioma, it is not known to what extent these usually benign tumors secrete EVs and how these EVs reflect the tumor. Here we report the first study that analyzed meningioma cell-derived EVs.

METHODS

Meningioma tissue, short-term cell cultures and cell culture-derived EVs (menEVs), (n=4) were analyzed by global mass-spectromety, immunoblotting and imaging flow cytometry and compared to EVs from glioblastoma short-term cell cultures (gEVs), (n=4). Plasma EVs from meningioma patients (n = 12) were analyzed for their tetraspanin marker expression (CD9, CD81 and CD63). EVs were further analyzed by nanoparticle analysis (NTA) and electron microscopy.

RESULTS

menEVs were 110-140nm in size and exhibited vesicular structures by electron microscopy. We identified 269 proteins in menEVs through mass spectometry. 45 proteins were upregulated in menEVs compared to short-term cell culture and original tumor tissue. 99 proteins were exclusively found in menEVs compared to gEVs, with osteopontin being the top highly expressed protein within the mEV fraction. Both meningioma and glioblastoma patients have elevated circulating plasma EV counts (p< 0.01), as measured by NTA.

CONCLUSION

The increase in circulating plasma EVs in meningioma patients suggests that tumor cell-derived EVs augment the pool of circulating EVs and could be utilized to obtain information on the tumor by liquid biopsy. Osteopontin is known to be expressed at high levels in meningiomas and its association with menEVs may facilitate isolation of circulating meningioma-specific EVs for analysis.

GENE-22. GENOME-WIDE METHYLATION PROFILING OF GLIOBLASTOMA EXTRACELLULAR VESICLE DNA ALLOWS TUMOR CLASSIFICATION

BACKGROUND

Genome-wide methylation profiling has recently been developed into a tool that allows subtype tumor classification in central nervous system (CNS) tumors. Extracellular vesicles (EVs) are released by CNS tumor cells and contain high molecular weight tumor DNA, rendering EVs a potential biomarker source to identify tumor subgroups, stratify patients and monitor therapy by liquid biopsy. We investigated whether the DNA in glioma-derived EVs reflects genome-wide tumor methylation profiles and allows tumor subtype classification.

METHODS

DNA was isolated from EVs secreted by cultured glioma stem-like cells (GSC) as well as from the cells of origin and from the original tumor samples (n=3 patients). EVs were classified by nanoparticle analysis (NTA), immunoblotting, imaging flow cytometry (IFCM), multiplex EV assays and electron microscopy. Genome-wide DNA methylation profiling was performed using an 850k Illumina EPIC array and results were classified according to the DKFZ brain tumor classifier.

RESULTS

The size range of GSC-derived EVs was 120–150 nm, as measured by NTA. The majority of secreted EVs exhibited high expression of common EV markers (i.e. CD9, CD63 and CD81), as characterized by IFCM and multiplex EV assays. Genome-wide methylation profiling of GSC-derived EVs correctly identified the methylation class of the original tumor, including information on the IDH mutation status and subclass classification (RTK1, RTK2). In addition, copy number alterations and the MGMT metyhlation status matched the pattern of the parental GSCs and original tumor samples.

CONCLUSION

EV DNA faithfully reflects the tumor methylation class as well as the MGMT methylation status and copy number variations present in the parental cells and the original tumor. Methylation profiling of circulating tumor EV DNA could become a useful tool to detect and classify CNS tumors.

CBMT-12. FOCAD LOSS IMPACTS MICROTUBULE ASSEMBLY, G2/M PROGRESSION AND PATIENT SURVIVAL IN ASTROCYTIC GLIOMAS

In search of novel genes associated with glioma pathogenesis, we have previously shown that KIAA1797/FOCAD is frequently deleted in malignant gliomas and that the encoded focadhesin functions as a tumor suppressor impacting proliferation and migration of glioma cells in vitro and in vivo. Here, we examine an association of FOCAD copy number loss with overall survival of patients with astrocytic gliomas, and address the molecular mechanisms that govern the suppressive effect of focadhesin on glioma growth. FOCAD loss was associated with inferior outcome in patients with isocitrate dehydrogenase 1 or 2 (IDH)-mutant astrocytic gliomas of WHO grades II-IV. Multivariate analysis considering age at diagnosis, IDH mutation and MGMT promoter methylation status confirmed FOCAD loss as a prognostic factor for overall survival. Using a yeast two-hybrid screen and pull-down assays, we identified tubulin beta-6 and other tubulin family members as novel focadhesin-interacting partners. We demonstrate that tubulins and focadhesin co-localize at the centrosome and that focadhesin is enriched in proximity to centrioles. Focadhesin is recruited to microtubules via its interaction partner SLAIN motif family member 2 and reduces microtubule assembly rates, possibly explaining why focadhesin decreases cell migration. During the cell cycle, focadhesin levels peak in G2/M phase and influence time-dependent G2/M progression possibly via polo like kinase 1 phosphorylation, providing an explanation for focadhesin-dependent cell growth reduction. We conclude that FOCAD loss may promote biological aggressiveness and worsen clinical outcome of diffuse astrocytic gliomas by enhancing microtubule assembly and accelerating G2/M phase progression.

PATH-53. IMMUNOLOGICAL PROFILING OF MUTATIONAL AND TRANSCRIPTIONAL SUBGROUPS IN PEDIATRIC AND ADULT HIGH-GRADE GLIOMAS

Immunological treatment strategies, including checkpoint inhibition, are currently under investigation for high-grade gliomas, but their success is limited. Hence, it is crucial to determine immunological pathways that can be targeted and to identify subgroups of patients likely to benefit from immunotherapies. Previous studies are still limited by comparably small sample sizes and there is only few data about specific immunological mechanisms in pediatric high-grade glioma. We gathered published gene expression data from 1135 adult and pediatric high-grade gliomas and applied a machine learning technique to determine their mutational (K27, G34, IDHmut, IDHwt) and transcriptional subtype. Subsequently, immune cell infiltration and functional immune pathway signatures were evaluated in correlation to histological diagnosis, age, transcriptional and mutational subtype. T-SNE analysis and unsupervised hierarchical clustering was applied to detect subgroup-specific immune microenvironments across all high-grade glioma subtypes. Four distinct microenvironmental phenotypes of immune cell infiltration were identified, which can be stratified into vascular, monocytic/stromal, monocytic/T-cell and APC/NK/T-cell dominant immune clusters. Immune cell infiltration correlated strongly with transcriptional and mutational subtypes but was independent of age and histological diagnosis (p< 0.01). H3F3A mutated tumors had significantly fewer tumor infiltrating lymphocytes and macrophages. By including functional pathways and correlating the expression of immunostimulatory and inhibitory receptor/ligand interactions, we were able to define the immunological microenvironment and to identify possible immunological subtypes associated with poor prognosis as well as subtypes that might be especially amenable to checkpoint inhibition. In addition, comparisons of overall survival with the immunological microenvironment and specifically with immune checkpoint molecules revealed diverse correlations within the transcriptional and mutational subgroups. In conclusion, we shat that mutational and transcriptional subgroups of pediatric and adult high-grade gliomas are characterized by distinct immunological tumor microenvironments. Our analysis demonstrates the immunological heterogeneity within this entity and emphasizes an immune specific stratification of subgroups for upcoming immunotherapy trials.

MNGI-02. FEATURES OF TUMOR TEXTURE INFLUENCE SURGERY AND OUTCOME IN INTRACRANIAL MENINGIOMA

OBJECTIVE

Texture-related factors such as consistency, vascularity and adherence vary considerably in meningioma and are thought to be linked with surgical resectability and morbidity. However, data analyzing the true impact of meningioma texture on the surgical management is sparse.

METHODS

Patients with intracranial meningioma treated between 08/2014-04/2018 were prospectively collected for demographics and surgical treatment with related morbidity and extend of resection (EOR). Tumor characteristics were reported by the surgeon using a standardized questionnaire including items such as tumor rigidity, homogeneity, vascularization and adherence to surrounding neurovascular structure and analyzed for their impact on EOR and neurological outcome using multivariate regression analyses.

RESULTS

296 patients (214 female (72.3%) with intracranial meningiomas were included with a mean age of 60.4 years. 23% of patients had a transient and 6.1% permanent neurological deficits and three patients (1.1%) died. The occurrence of a neurological deficit was associated with duration of surgery (p = 0.013) and tumor adherence to neurovascular structures (p = 0.014). Similar associations were observed in subgroup analyses of different tumor localizations (e.g. convexity and skull base). With regard to EOR, the tumor adherence (p < 0.001) and recurrent surgery (p = 0.001) were found as independent predictors for subtotal resection. Noteworthy, the tumor rigidity had no significant impact on the morbidity or EOR.

CONCLUSION

Our analysis supports the notion that tumor texture has an impact on the surgical management of meningioma and provides sound data that tumor adherence is a significant factor influencing neurological outcome and EOR. In contrast, the influence of tumor rigidity has less impact than previously thought. Preoperative prediction of tumor texture is therefore required for optimized risk assessment.

IMMU-40. CANCER IMMUNOEDITING SHAPES THE IMMUNE ESCAPE SIGNATURE AND CLONAL ARCHITECTURE IN GLIOMAS

Immunotherapeutic strategies are increasingly important in neuro-oncology, and the elucidation of escape mechanisms which lead to treatment resistance is crucial. Understanding heterogeneous clonal dynamics and emergence of immune escape variants during cancer immunoediting can yield valuable insights into the adaptive processes governing treatment resistance. We applied a recently developed multicolor labeling strategy termed optical barcoding to compare in vivo clonality in an immunocompetent vs immunodeficient environment. Optically barcoded GL261 glioma cells were implanted in parallel into the brains of i) wildtype (wt) C57BL/6 mice, ii) immunodeficient Pfp-/- Rag2-/- mice or iii) PD1-/- mice and tumor growth was monitored. Ex vivo analysis of individual tumor clones revealed that tumors in immunocompetent mice had a profoundly different clonal architecture compared to immunodeficient mice. Whereas tumors in pfp-/- rag2-/- mice exhibited a highly polyclonal composition, immunoedited tumors in wt and PD1-/- mice showed reduced clonality with emergence of immune escape clones, independent of in vitro proliferation rates. Survival of wt mice was significantly longer than of Pfp-/- Rag2-/- mice and was even more prolonged in PD1-/- mice. Immunoediting in immunocompetent mice was further associated with striking differences in vascularity and invasiveness. Time-course microarray analyses, flow-cytometric phenotyping of tumor-infiltrating immune cells and immunostaining highlighted the role of PD-L1 and other immunosuppressive mediators as mechanisms to adapt to T-cell infiltration and IFN-ɣ production. Furthermore, RNAseq profiling of FACS-separated tumor cells, T cells and macrophages/microglia allowed the identification of IFN-ɣ-mediated T-cell-shaped gene expression signatures and of new pathways potentially involved in the immune escape of gliomas. To conclude, the process of cancer immunoediting during tumor evolution not only shapes gene expression profiles and growth patterns, but also has a profound impact on the intratumoral clonal heterogeneity in malignant gliomas.

A comparison between threshold criterion and amplitude criterion in transcranial motor evoked potentials during surgery for supratentorial lesions

OBJECTIVE

The aim of this study was to compare sensitivity and specificity between the novel threshold and amplitude criteria for motor evoked potentials (MEPs) monitoring after transcranial electrical stimulation (TES) during surgery for supratentorial lesions in the same patient cohort.

METHODS

One hundred twenty-six patients were included. All procedures were performed under general anesthesia. Craniotomies did not expose motor cortex, so that direct mapping was less suitable. After TES, MEPs were recorded bilaterally from abductor pollicis brevis (APB), from orbicularis oris (OO), and/or from tibialis anterior (TA). The percentage increase in the threshold level was assessed and considered significant if it exceeded by more than 20% on the affected side the percentage increase on the unaffected side. Amplitude on the affected side was measured with a stimulus intensity of 150% of the threshold level set for each muscle.

RESULTS

Eighteen of 126 patients showed a significant change in the threshold level as well as an amplitude reduction of more than 50% in MEPs recorded from APB, and 15 of the patients had postoperative deterioration of motor function of the arm (temporary in 8 cases and permanent in 7 [true-positive and false-negative results]). Recording from TA was performed in 66 patients; 4 developed postoperative deterioration of motor function of the leg (temporary in 3 cases and permanent in 1), and showed a significant change in the threshold level, and an amplitude reduction of more than 50% occurred in 1 patient. An amplitude reduction of more than 50% occurred in another 10 patients, without a significant change in the threshold level or postoperative deterioration. Recording from OO was performed in 61 patients; 3 developed postoperative deterioration of motor function of facial muscles (temporary in 2 cases and permanent in 1) and had a significant change in the threshold level, and 2 of the patients had an amplitude reduction of more than 50%. Another 6 patients had an amplitude reduction of more than 50% but no significant change in the threshold level or postoperative deterioration.Sensitivity of the threshold criterion was 100% when MEPs were recorded from APB, OO, or TA, and its specificity was 97%, 100%, and 100%, respectively. Sensitivity of the amplitude criterion was 100%, 67%, and 25%, with a specificity of 97%, 90%, and 84%, respectively.

CONCLUSIONS

The threshold criterion was comparable to the amplitude criterion with a stimulus intensity set at 150% of the threshold level regarding sensitivity and specificity when recording MEPs from APB, and superior to it when recording from TA or OO.

The secreted glycolytic enzyme GPI/AMF stimulates glioblastoma cell migration and invasion in an autocrine fashion but can have anti-proliferative effects

Background

Aerobic glycolysis confers several advantages to tumor cells, including shunting of metabolites into anabolic pathways. In glioblastoma cells, hypoxia induces a flux shift from the pentose phosphate pathway toward glycolysis and a switch from proliferation to migration. The mechanistic link between glycolysis and migration is poorly understood. Since glucose-6-phosphate isomerase (GPI) is identical to the secreted cytokine autocrine motility factor (AMF), we investigated whether GPI/AMF regulates glioblastoma cell invasion.

Methods

The expression and hypoxic regulation of GPI/AMF and its receptor AMFR were analyzed in glioblastoma tissue and cell lines. Functional effects were studied in vitro and in xenograft models.

Results

High GPI/AMF expression in glioblastomas was found to be associated with a worse patient prognosis, and levels were highest in hypoxic pseudopalisades. Hypoxia upregulated both GPI/AMF and AMFR expression as well as GPI/AMF secretion in vitro. GPI/AMF stimulated cell migration in an autocrine fashion, and GPI/AMF expression was upregulated in migratory cells but reduced in rapidly proliferating cells. Knockdown or inhibition of GPI/AMF reduced glioblastoma cell migration but in part stimulated proliferation. In a highly invasive orthotopic glioblastoma model, GPI/AMF knockdown reduced tumor cell invasion but did not prolong survival. In a highly proliferative model, knockdown tumors were even larger and more proliferative than controls; however, perivascular invasion, provoked by simultaneous bevacizumab treatment, was reduced.

Conclusions

GPI/AMF is a potent motogen for glioblastoma cells, explaining in part the association between glycolysis and migration. Targeting GPI/AMF is, however, problematic, since beneficial anti-invasive effects may be outweighed by unintended mitogenic effects.

Key Points

1.Increased glycolysis is linked with increased cell migration and invasion in glioblastoma cells. 2.The glycolysis enzyme GPI/AMF may serve as a target for antimetabolic and anti-invasive therapy. 3.Despite reducing tumor invasion, GPI/AMF targeting may have unwanted growth stimulatory effects.

DNA methylation-based classification of ependymomas in adulthood: implications for diagnosis and treatment

Background

Ependymal tumors are glial tumors that commonly manifest in children and young adults. Their classification has remained entirely morphological until recently, and surgery and radiotherapy are the main treatment options, especially in adults. Here we sought to correlate DNA methylation profiles with clinical and pathological characteristics in the prospective cohort of the German Glioma Network.

Methods

Tumors from 122 adult patients with myxopapillary ependymoma, ependymoma, anaplastic ependymoma, subependymoma, or RELA fusion-positive ependymoma classified according to the World Health Organization (WHO) 2016 were subjected to DNA methylation profiling using the Illumina HumanMethylation450 BeadChip platform. Molecular data were correlated with histologic features and clinical characteristics.

Results

At a median follow-up of 86.7 months, only 22 patients experienced progression (18.0%) and 13 patients (10.7%) died. Each tumor could be assigned to one of the previously defined molecular ependymoma subgroups. All histologic subependymomas corresponded to subependymoma (SE) DNA methylation subgroups, but the reverse was not true: 19 histologic ependymomas (WHO grade II) were allocated to molecular SE groups. Similarly, all histological myxopapillary ependymomas were assigned to the molecularly defined spinal myxopapillary ependymoma (SP-MPE) class, but this molecular subgroup additionally included 15 WHO grade II ependymomas by histology. Overall, WHO grade II ependymomas distributed into 7 molecular subgroups.

Conclusion

Most adult patients with ependymoma show a favorable prognosis. Molecular classification may provide diagnostic and prognostic information beyond histology and facilitate patient stratification in future clinical trials. The prognostic significance of a subependymoma or myxopapillary ependymoma DNA methylation phenotype without corresponding histology requires further study.

Key Points

1. Ependymoma diagnosed in adult patients most often shows a good prognosis. 2. Molecular classification can support diagnostic and prognostic information beyond histology.

Tectal gliomas: assessment of malignant progression, clinical management, and quality of life in a supposedly benign neoplasm

OBJECTIVE Tectal gliomas constitute a rare and inhomogeneous group of lesions with an uncertain clinical course. Because these supposedly benign tumors are frequently followed up by observation over many years, the authors undertook this analysis of their own case series in an effort to demonstrate that the clinical course is highly variable and that there is a potential for a progressive biology. METHODS Clinical data analysis of 23 cases of tectal glioma (involving 9 children and 14 adults) was performed retrospectively. Radiographic data were analyzed longitudinally and MR images were evaluated for tumor volume, contrast enhancement, and growth progression. Quality of life was assessed using the EORTC BN20 and C30 questionnaires during follow-up in a subgroup of patients. RESULTS The patients' mean age at diagnosis was 29.2 years. The main presenting symptom at diagnosis was hydrocephalus (80%). Six patients were treated by primary tumor resection (26.1%), 3 patients underwent biopsy followed by resection (13.1%), and 3 patients underwent biopsy only (13.1%). For additional treatment of hydrocephalus, 14 patients (60.9%) received shunts and/or endoscopic third ventriculostomy. Radiographic tumor progression was observed in 47.9% of the 23 cases. The mean time between diagnosis and growth progression was 51.5 months, and the mean time to contrast enhancement was 69.7 months. Histopathological analysis was obtained in 12 cases (52.2%), resulting in 5 cases of high-grade glioma (3 cases of glioblastoma multiforme [GBM], grade IV, and 2 of anaplastic astrocytoma, grade III), 5 cases of pilocytic astrocytoma, 1 diffuse astrocytoma, and 1 ganglioglioma. Malignant progression was observed in 2 cases, with 1 case progressing from a diffuse astrocytoma (grade II) to a GBM (grade IV) within a period of 13 years. Quality-of-life measurements demonstrated distinct functional deficits compared to a healthy sample as well as glioma control cohorts. CONCLUSIONS Analysis of this case series shows that a major subpopulation of tectal gliomas show progression and malignant transformation in children as well as in adolescents. These tumors therefore cannot be considered inert lesions and require histological confirmation and close follow-up. Quality-of-life questionnaires show that tectal glioma patients might benefit from special psychological support in emotional, social, and cognitive functionality.

P14.108 Bevacizumab versus alkylating chemotherapy in recurrent glioblastoma

BACKGROUND

The use of alkylating chemotherapy versus bevacizumab for recurrent glioblastoma remains controversial. Here we tested the hypothesis that the activity of alkylators, but not that of bevacizumab, would be associated with the O6-methylguanine DNA methyltransferase (MGMT) promoter methylation status

PATIENTS AND METHODS

We analyzed a cohort of patients treated at centers of the German Glioma Network or the University Hospital Zurich with alkylating agent-based chemotherapy (n=260) or bevacizumab without or with irinotecan (n=84) for first recurrence of glioblastoma. Outcome was stratified for MGMT status and cross-over to bevacizumab or alkylators at further tumor progression.

RESULTS

Median post-recurrence survival-1 (PRS-1) for patients receiving alkylating agent chemotherapy at first recurrence was longer than for patients receiving bevacizumab (11.1 versus 7.4 months, p<0.001). The use of alkylating agents was associated with longer PRS-1 for patients with a methylated versus an unmethylated MGMT promoter (p=0.017). For patients receiving bevacizumab, PRS-1 was not different with or without MGMT promoter methylation. PRS-1 was longer in the group receiving alkylating chemotherapy compared to bevacizumab for patients with a methylated (p<0.001) or unmethylated MGMT promoter (p=0.034). For patients with alkylators at first recurrence receiving bevacizumab at any further recurrence, PRS-1 was longer than in patients receiving bevacizumab first and alkylators thereafter (p=0.002).

CONCLUSION

This study confirms limited value of bevacizumab in recurrent glioblastoma independent of MGMT status. Alkylating agents have activity in recurrent glioblastoma, especially in the context of a methylated MGMT promoter.

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.

Clonality of circulating tumor cells in breast cancer brain metastasis patients

Background

The incidence of brain metastases in breast cancer (BCBM) patients is increasing. These patients have a very poor prognosis, and therefore, identification of blood-based biomarkers, such as circulating tumor cells (CTCs), and understanding the genomic heterogeneity could help to personalize treatment options.

Methods

Both EpCAM-dependent (CellSearch® System) and EpCAM-independent Ficoll-based density centrifugation methods were used to detect CTCs from 57 BCBM patients. DNA from individual CTCs and corresponding primary tumors and brain metastases were analyzed by next-generation sequencing (NGS) in order to evaluate copy number aberrations and single nucleotide variations (SNVs).

Results

CTCs were detected after EpCAM-dependent enrichment in 47.7% of the patients (≥ 5 CTCs/7.5 ml blood in 20.5%). The CTC count was associated with ERBB2 status (p = 0.029) of the primary tumor as well as with the prevalence of bone metastases (p = 0.021). EpCAM-independent enrichment revealed CTCs in 32.6% of the patients, especially among triple-negative breast cancer (TNBC) patients (70.0%). A positive CTC status after enrichment of either method was significantly associated with decreased overall survival time (p < 0.05). Combining the results of both enrichment methods, 63.6% of the patients were classified as CTC positive. In three patients, the matched tumor tissue and single CTCs were analyzed by NGS showing chromosomal aberrations with a high genomic clonality and mutations in pathways potentially important in brain metastasis formation.

Conclusion

The detection of CTCs, regardless of the enrichment method, is of prognostic relevance in BCBM patients and in combination with molecular analysis of CTCs can help defining patients with higher risk of early relapse and suitability for targeted treatment.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1184-2) contains supplementary material, which is available to authorized users.

Immunologic Profiling of Mutational and Transcriptional Subgroups in Pediatric and Adult High-Grade Gliomas

Immunologic treatment strategies are under investigation for high-grade gliomas. Determining relevant immunologic pathways is required for invigorating a tumor-specific immune response. We therefore investigated the immunologic phenotypes within different subgroups of high-grade gliomas, with a focus on rare genetic subgroups of pediatric and adolescent patients to identify potentially targetable mechanisms. We gathered published gene-expression data from 1,135 high-grade glioma patients and applied a machine-learning technique to determine their transcriptional (mesenchymal, classic, neural, and proneural) and mutational [K27, G34, IDH, and wild type (WT)] subtypes. Gene signatures of infiltrating immune cells and functional immune pathways were evaluated in correlation to histologic diagnosis, age, and transcriptional and mutational subgroups. Our analysis identified four distinct microenvironmental signatures of immune cell infiltration (immune 1-4), which can be stratified into vascular, monocytic/stromal, monocytic/T-cell-, and antigen-presenting cell (APC)/natural killer (NK) cell/T-cell-dominated immune clusters. Immune cell expression profiles correlated with transcriptional and mutational subgroups but were independent of age and histologic diagnosis. By including functional pathways and correlating the expression of immunostimulatory and -inhibitory receptor-ligand interactions, we were able to define the immunologic microenvironment and identify possible immunologic subtypes associated with poor prognosis. In addition, comparison of overall survival with the immunologic landscape and with checkpoint molecules revealed correlations within the transcriptional and mutational subgroups, highlighting the potential application of PD-1/PD-L1 checkpoint inhibition in K27-mutated tumors. Our study shows that transcriptional and mutational subgroups are characterized by distinct immunologic tumor microenvironments, demonstrating the immunologic heterogeneity within high-grade gliomas and suggesting an immune-specific stratification for upcoming immunotherapy trials.

Intraocular pressure during neurosurgical procedures in context of head position and loss of cerebrospinal fluid

OBJECTIVE

Perioperative visual loss (POVL) is a rare but serious complication in surgical disciplines, especially in spine surgery. The exact pathophysiology of POVL remains unclear, but elevated intraocular pressure (IOP) is known to be part of it. As POVL is rarely described in patients undergoing intracranial or intradural surgery, the aim of this study was to investigate the course of IOP during neurosurgical procedures with opening of the dura mater and loss of CSF.

METHODS

In this prospective, controlled trial, 64 patients fell into one of 4 groups of 16 patients each. Group A included patients undergoing spine surgery in the prone position, group B patients had intracranial procedures in the prone position, and group C patients were treated for intracranial pathologies in a modified lateral position with the head rotated. In groups A-C, the dura was opened during surgery. Group D patients underwent spine surgeries in the prone position with an intact dura. IOP was measured continuously pre-, peri-, and postoperatively.

RESULTS

In all groups, IOP decreased after induction of anesthesia and increased time dependently after final positioning for the operation. The maximum IOP in group A prior to opening of the dura was 28.6 ± 6.2 mm Hg and decreased to 23.44 ± 4.9 mm Hg directly after dura opening (p < 0.0007). This effect lasted for 30 minutes (23.5 ± 5.6 mm Hg, p = 0.0028); after 60 minutes IOP slowly increased again (24.5 ± 6.3 mm Hg, p = 0.15). In group B, the last measured IOP before CSF loss was 28.1 ± 5.0 mm Hg and decreased to 23.5 ± 6.1 mm Hg (p = 0.0039) after dura opening. A significant IOP decrease in group B lasted at 30 minutes (23.6 ± 6.0 mm Hg, p = 0.0039) and 60 minutes (23.7 ± 6.0 mm Hg, p = 0.0189). In group C, only the lower eye showed a decrease in IOP up to 60 minutes after loss of CSF (opening of dura, p = 0.0007; 30 minutes, p = 0.0477; 60 minutes, p = 0.0243). In group D (control group), IOP remained stable throughout the operation after the patient was prone.

CONCLUSIONS

This study is the first to demonstrate that opening of the dura with loss of CSF during neurosurgical procedures results in a decrease in IOP. This might explain why POVL predominantly occurs in spinal but rarely in intracranial procedures, offers new insight to the pathophysiology of POVL, and provides the basis for further research and treatment of POVL.German Clinical Trials Register (DRKS) no.: DRKS00007590 (drks.de).

Abstract 1114: Upregulation of ALCAM is a marker for non-small-cell lung cancer brain metastases

Non-small-cell lung cancer (NSCLC) is the most common cause of cancer-related death with still a 5-year survival rate of &lt;10%. Every second patient with advanced NSCLC will develop brain metastases and in 50% of those the brain is the only site of tumor relapse (oligo-metastasis). Cancer cells need to have specific properties to access and colonize the brain microenvironment leading to the question which metastatic factors foster brain metastasis formation. Different cell adhesion molecules (CAMs) have been shown to be involved in the process of metastasis in different tumor entities. The activated leukocyte cell adhesion molecule (ALCAM) is a type I transmembrane protein of the immunoglobulin superfamily and involved in the maintenance of cell-cell contacts and has a possible role in the “homing” of metastatic cells in distant organs. ALCAM is also involved in the leukocyte transmigration across the blood-brain barrier. Here we therefore investigated the role of ALCAM in NSCLC brain metastases formation. Our studies on patient material revealed that the ALCAM protein expression in brain metastases (n=71) is significantly increased (50.7% positive, p=0.023) compared to the primary tumor (21.7% positive, n=47). Analysis of matched pairs of primary tumors and brain metastases confirmed this observation, as in 33% a de novo ALCAM expression in the matching brain metastases could be observed. Additionally, patients with a strong ALCAM expression in either their primary tumors or brain metastases showed a significantly shortened overall survival (p=0.017 and p=0.035 respectively). In vitro analysis of the effect of ALCAM knock out in the H460 lung cancer cell line showed no effect on proliferation, migration or colony-forming behavior. However, cell adhesion was severely hampered in the knock out cells. Currently in vivo mice experiments are running. Together these findings indicate an important role for ALCAM in brain metastasis formation.

Citation Format: Desiree Loreth, Justine Münsterberg, Cecile Maire, Stefan Werner, Monja Gandrass, Christian Bernreuther, Jolanthe Kropidlowski, Manfred Westphal, Stefan Steurer, Katrin Lamszus, Markus Glatzel, Klaus Pantel, Harriet Wikman. Upregulation of ALCAM is a marker for non-small-cell lung cancer brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1114.

Relapse of a group 4 medulloblastoma after 18 years as proven by histology and DNA methylation profiling

BACKGROUND

Recent studies on medulloblastomas (MB) suggest that a large fraction of tumors appearing as late recurrence turn out to be secondary malignancies, e.g., malignant gliomas, after thorough molecular investigation.

RESULTS

Here, we report of a patient with a group 4 MB that developed a distant recurrence after more than 18 years. The recurrent tumor was confirmed by histology and genome-wide DNA methylation profiling.

CONCLUSION

Our case not only illustrates the potential of very late recurrences after seemingly cured group 4 MB, but also illustrates that detailed molecular analyses are indispensable in patients with a history of a previous malignancy.

Postoperative Nausea and Vomiting Following Craniotomy: Risk Factors and Complications in Context of Perioperative High-dose Dexamethasone Application

Introduction Postoperative nausea and vomiting (PONV) is common in patients after craniotomy and may lead to severe postoperative complications. The aim of this study was to identify risk factors and postoperative complications associated with PONV in the context of perioperative high-dose dexamethasone administration.

Patients and Methods In this prospective single-center study, all patients planned for elective craniotomy for supra- and infratentorial lesions were eligible to be included. Any PONV in a 24-hour period after craniotomy was recorded and analyzed with regard to time to postoperative complications and the administration of perioperatively administered high-dose dexamethasone.

Results The overall PONV rate of 421 patients during a 9-month period was 18.1% (76 patients). Multivariate analysis revealed a significant association of PONV with female sex, infratentorial localization, age, and history of PONV. There was no association between PONV and postoperative complications such as intracranial hemorrhage, cerebrospinal fluid (CSF) leaks, or pneumonia. Perioperative administration of high-dose dexamethasone for prophylactic prevention of edema was the only significant risk factor for postoperative complications (odds ratio [OR]: 3.34; confidence interval [CI], 1.39–8.05; p < 0.01) with a highly significant association with the occurrence of CSF leaks (OR: 6.85; CI, 1.62–29.05; p < 0.01).

Conclusion The low PONV rate of 18.1% in this study may be the result of the frequent perioperative administration of high-dose dexamethasone for the prevention of edema. Our data indicate that perioperative high-dose dexamethasone is significantly associated with CSF leaks and can therefore not be recommended on a regular basis.

Imaging flow cytometry facilitates multiparametric characterization of extracellular vesicles in malignant brain tumours

Cells release heterogeneous nano-sized vesicles either as exosomes, being derived from endosomal compartments, or through budding from the plasma membrane as so-called microvesicles, commonly referred to as extracellular vesicles (EVs). EVs are known for their important roles in mammalian physiology and disease pathogenesis and provide a potential biomarker source in cancer patients. EVs are generally often analysed in bulk using Western blotting or by bead-based flow-cytometry or, with limited parameters, through nanoparticle tracking analysis. Due to their small size, single EV analysis is technically highly challenging. Here we demonstrate imaging flow cytometry (IFCM) to be a robust, multiparametric technique that allows analysis of single EVs and the discrimination of distinct EV subpopulations. We used IFCM to analyse the tetraspanin (CD9, CD63, CD81) surface profiles on EVs from human and murine cell cultures as well as plasma samples. The presence of EV subpopulations with specific tetraspanin profiles suggests that EV-mediated cellular responses are tightly regulated and dependent on cell environment. We further demonstrate that EVs with double positive tetraspanin expression (CD63+/CD81+) are enriched in cancer cell lines and patient plasma samples. In addition, we used IFCM to detect tumour-specific GFP-labelled EVs in the blood of mice bearing syngeneic intracerebral gliomas, indicating that this technique allows unprecedented disease modelling. In summary, our study highlights the heterogeneous and adaptable nature of EVs according to their marker profile and demonstrates that IFCM facilitates multiparametric phenotyping of EVs not only in vitro but also in patient plasma at a single EV level, with the potential for future functional studies and clinically relevant applications. Abbreviation: EDTA = ethylenediamine tetraacetic acid.

Synchronised spiking activity underlies phase amplitude coupling in the subthalamic nucleus of Parkinson's disease patients

Both phase-amplitude coupling (PAC) and beta-bursts in the subthalamic nucleus have been significantly linked to symptom severity in Parkinson's disease (PD) in humans and emerged independently as competing biomarkers for closed-loop deep brain stimulation (DBS). However, the underlying nature of subthalamic PAC is poorly understood and its relationship with transient beta burst-events has not been investigated. To address this, we studied macro- and micro electrode recordings of local field potentials (LFPs) and single unit activity from 15 hemispheres in 10 PD patients undergoing DBS surgery. PAC between beta phase and high frequency oscillation (HFO) amplitude was compared to single unit firing rates, spike triggered averages, power spectral densities, inter spike intervals and phase-spike locking, and was studied in periods of beta-bursting. We found a significant synchronisation of spiking to HFOs and correlation of mean firing rates with HFO-amplitude when the latter was coupled to beta phase (i.e. in the presence of PAC). In the presence of PAC, single unit power spectra displayed peaks in the beta and HFO frequency range and the HFO frequency was correlated with that in the LFP. Furthermore, inter spike interval frequencies peaked in the same frequencies for which PAC was observed. Finally, PAC significantly increased with beta burst-duration. Our findings offer new insight in the pathology of Parkinson's disease by providing evidence that subthalamic PAC reflects the locking of spiking activity to network beta oscillations and that this coupling progressively increases with beta-burst duration. These findings suggest that beta-bursts capture periods of increased subthalamic input/output synchronisation in the beta frequency range and have important implications for therapeutic closed-loop DBS.

Positive End-expiratory Pressure Ventilation Increases Extravascular Lung Water Due to a Decrease in Lung Lymph Flow

Positive end-expiratory pressure (PEEP) is used to improve gas exchange, increase functional residual capacity, recruit air spaces, and decrease pulmonary shunt in patients suffering from respiratory failure. The effect of PEEP on extravascular lung water (EVLW), however, is still not fully understood. This study was designed as a prospective laboratory experiment to evaluate the effects of PEEP on EVLW and pulmonary lymph flow (QL) under physiologic conditions.

Twelve adult sheep were operatively prepared to measure haemodynamics of the systemic and pulmonary circulation, and to assess EVLW. In addition, the lung lymphatic duct was cannulated and a tracheostomy performed. The animals were then mechanically ventilated in the awake-state without end-expiratory pressure (PEEP 0). After a two-hour baseline period, PEEP was increased to 10 cmH2O for the duration of two hours, and then reduced back to 0 cmH2O. Cardiopulmonary variables, QL, and arterial blood gases were recorded intermittently; EVLW was determined two hours after each change in PEEP.

The increase in PEEP resulted in a decrease in QL (7±1 vs 5±1 ml/h) and an increase in EVLW (498±40 vs 630±58 ml; P<0.05 each) without affecting cardiac output. As PEEP was decreased back to baseline, QL increased significantly (5±1 vs 10±2 ml/h), whereas EVLW returned back to baseline.

This study suggests that institution of PEEP produces a reversible increase in EVLW that is linked to a decrease in QL.

Observed versus expected mortality in pediatric patients intubated in the field with Glasgow Coma Scale scores < 9

PURPOSE

A Glasgow Coma Scale (GCS) score of 8 or less in patients suffering from severe traumatic brain injury (TBI) represents a decision-making marker in terms of intubation. This study evaluated the impact of prehospital intubation on the mortality of these TBI cases among different age groups.

METHODS

This study included the data from patients predominantly suffering from severe TBI [Abbreviated Injury Scale (AIS) of the head ≥ 3, GCS score < 9, Injury Severity Score (ISS) > 9] who were registered in TraumaRegister DGU^® from 2002 to 2013. An age-related analysis of five subgroups was performed (1-6, 7-15, 16-55, 56-79, and ≥ 80 years old). The observed and expected mortality were matched according to the Revised Injury Severity Classification, version II.

RESULTS

A total of 21,242 patients were included. More often, the intubated patients were severely injured when compared to the non-intubated patients (median ISS 29, IQR 22-41 vs. 24, IQR 16-29, respectively), with an associated higher mortality (42.2% vs. 30.0%, respectively). When compared to the calculated expected mortality, the observed mortality was significantly higher among the intubated patients within the youngest subgroup (42.2% vs. 33.4%, respectively; p = 0.03).

CONCLUSIONS

The observed mortality in the intubated children 1-6 years old suffering from severe TBI seemed to be higher than expected. Whether or not a GCS score of 8 or less is the only reliable criterion for intubation in this age group should be investigated in further trials.

Frequency of Circulating Tumor Cells (CTC) in Patients with Brain Metastases: Implications as a Risk Assessment Marker in Oligo-Metastatic Disease

Forty percent of non-small cell lung cancer (NSCLC) patients develop brain metastases, resulting in a dismal prognosis. However, patients in an oligo-metastatic brain disease setting seem to have better outcomes. Here, we investigate the possibility of using circulating tumor cells (CTCs) as biomarkers to differentiate oligo-metastatic patients for better risk assessment. Using the CellSearch® system, few CTCs were detected among NSCLC patients with brain metastases (n = 52, 12.5% ≥ two and 8.9% ≥ five CTC/7.5 mL blood) and especially oligo-metastatic brain patients (n = 34, 5.9%, and 2.9%). Still, thresholds of both ≥ two and ≥ five CTCs were independent prognostic indicators for shorter overall survival time among all of the NSCLC patients (n = 90, two CTC ≥ HR: 1.629, p = 0.024, 95% CI: 1.137⁻6.465 and five CTC ≥ HR: 2.846, p = 0.0304, CI: 1.104⁻7.339), as well as among patients with brain metastases (two CTC ≥ HR: 4.694, p = 0.004, CI: 1.650⁻13.354, and five CTC ≥ HR: 4.963, p = 0.003, CI: 1.752⁻14.061). Also, oligo-brain NSCLC metastatic patients with CTCs had a very poor prognosis (p = 0.019). Similarly, in other tumor entities, only 9.6% of patients with brain metastases (n = 52) had detectable CTCs. Our data indicate that although patients with brain metastases more seldom harbor CTCs, they are still predictive for overall survival, and CTCs might be a useful biomarker to identify oligo-metastatic NSCLC patients who might benefit from a more intense therapy.

Distribution of EGFR amplification, combined chromosome 7 gain and chromosome 10 loss, and TERT promoter mutation in brain tumors and their potential for the reclassification of IDHwt astrocytoma to glioblastoma

EGFR amplification (EGFRamp), the combination of gain of chromosome 7 and loss of chromosome 10 (7+/10-), and TERT promoter mutation (pTERTmut) are alterations frequently observed in adult IDH-wild-type (IDHwt) glioblastoma (GBM). In the absence of endothelial proliferation and/or necrosis, these alterations currently are considered to serve as a surrogate for upgrading IDHwt diffuse or anaplastic astrocytoma to GBM. Here, we set out to determine the distribution of EGFRamp, 7+/10-, and pTERTmut by analyzing high-resolution copy-number profiles and next-generation sequencing data of primary brain tumors. In addition, we addressed the question whether combinations of partial gains on chromosome 7 and partial losses on chromosome 10 exhibited a diagnostic and prognostic value similar to that of complete 7+/10-. Several such combinations proved relevant and were combined as the 7/10 signature. Our results demonstrate that EGFRamp and the 7/10 signature are closely associated with IDHwt GBM. In contrast, pTERTmut is less specific for IDHwt GBM. We conclude that, in the absence of endothelial proliferation and/or necrosis, the detection of EGFRamp is a very strong surrogate marker for the diagnosis of GBM in IDHwt diffuse astrocytic tumors. The 7/10 signature is also a strong surrogate marker. However, care should be taken to exclude pleomorphic xanthoastrocytoma. pTERTmut is less restricted to this entity and needs companion analysis by other molecular markers to serve as a surrogate for diagnosing IDHwt GBM. A combination of any two of EGFRamp, the 7/10 signature and pTERTmut, is highly specific for IDHwt GBM and the combination of all three alterations is frequent and exclusively seen in IDHwt GBM.

Intrathecal penetration of meropenem and vancomycin administered by continuous infusion in patients suffering from ventriculitis-a retrospective analysis

BACKGROUND

Vancomycin and meropenem are frequently used as empiric treatment for ventriculitis. Penetration into the cerebrospinal fluid (CSF) depends on various factors with a high inter-individual variability. Because attaining and maintaining adequate concentrations of meropenem and vancomycin in the CSF is crucial for their bactericidal effect, we introduced a routine therapeutic drug monitoring (TDM) from CSF and serum for both antibiotics. We studied the antibiotic penetration into the CSF.

METHODS

Patient data including serum and CSF concentrations for meropenem and vancomycin were collected in a retrospective fashion. Antibiotic CSF penetration ratio was calculated for each patient. Antibiotics were administered by continuous infusion aiming for serum target concentrations of 20-30 mg/L for vancomycin and 16-32 mg/L for meropenem.

RESULTS

Twenty-two patients with 36 CSF/serum pairs for meropenem and 43 pairs for vancomycin were studied. No patient suffered from renal or liver insufficiency. Mean vancomycin serum concentration was 22 ± 8 mg/L and the mean CSF concentration 4.5 ± 2.6 mg/L. CSF penetration was 20 ± 11% (coefficient of determination (R²) 0.02). For meropenem, the mean serum concentration was 30.7 ± 14.9 mg/L, mean CSF concentration 5.5 ± 5.2 mg/L, and a penetration of 18 ± 12%, R² = 0.42.

CONCLUSION

Penetration of meropenem and vancomycin into the CSF is low while showing a high interindividual variability. Various patients in our study cohort were at risk for insufficient target attainment in CSF. Continuous administration of antibiotics under routine TDM appears to be a feasible and reasonable approach for optimization of intrathecal drug levels in patients suffering from ventriculitis. TDM might guide individual dosing adaptation and efforts to predict the CSF penetration of meropenem and vancomycin in cases of ventriculitis.

Complementary and alternative medicine use by glioma patients in Switzerland

Background

During the course of disease, most glioma patients learn that there is no cure for their tumor. It is therefore not uncommon for patients or caregivers to seek complementary and alternative medicine (CAM) treatments. Patterns of CAM use vary across the globe, but little is known about the type of, and motivation for, CAM use in most countries.

Methods

Here we conducted a cross-sectional survey of CAM use in patients harboring gliomas of World Health Organization (WHO) grades II to IV at 3 specialized neuro-oncology centers in Switzerland.

Results

Of 208 patients who returned the survey, approximately half reported having used or using CAM. CAM use was associated with younger age. Patients suffering from WHO grade II gliomas were less likely to indicate CAM use. The leading motivation for CAM use was to contribute actively to the treatment of the disease. CAM use was commonly not counseled or supervised by a health care professional. Cost and issues of reimbursement were not an important factor in the decision against or for CAM use.

Conclusions

Physicians caring for glioma patients should be aware of and explore CAM use to better understand patients' attitudes toward their disease, to provide counseling, and to identify potential interactions of CAM with standard treatments for gliomas.

Electrical Stimulation of the Anterior Thalamus for Epilepsy: Clinical Outcome and Analysis of Efficient Target

OBJECTIVE

Deep brain stimulation (DBS) of the anterior thalamic complex (ANT) is an adjunctive therapy for pharmacoresistant epilepsy. To define the most efficient target in DBS for epilepsy, we investigate clinical data, position of leads, usability of atlas data compared to electric field modeling based on programming parameters.

METHODS

Data from ten consecutive patients who underwent ANT-DBS were analyzed. The mammillothalamic tract (MTT), an internal landmark for direct stereotactic targeting, was segmented from MRI. Centers of stimulation were determined and their positions relative to ventricles and the MTT were analyzed. Two 3D thalamus atlases were transformed to segmented patient's thalami and proportions of activated nuclei were calculated.

RESULTS

Our data indicate higher response rates with a center of stimulation 5 mm lateral to the wall of the third ventricle (R² for reduction of focal seizure frequency and distance to the wall of the third ventricle = 0.48, p = 0.026). For reduction of focal seizures, a strong positive correlation with the dorsal distance to the midcommissural plane was found (R² = 0.66, p = 0.004). In one 3D atlas, stimulation of internal medullary lamina (IML) correlated strongly positive with response rates, which, however, did not reach statistical significance (R² = 0.69, p = 0.17 for tonic-clonic seizures). All electrical fields covered the diameter of the MTT. The position of the MTT in the thalamus was highly variable (range: x-coordinate 4.0 to 7.3 mm, y-coordinate -1.3 to 5.1 mm in AC-PC space).

CONCLUSIONS

The distance of the active contact to the lateral wall of the third ventricle, MTT and the ventrodorsal distance to midcommissural plane appear to be relevant for optimal target planning. For reduction of focal seizure frequency, we found best response rates with a center of stimulation 5 mm lateral to the wall of the third ventricle, and a lead tip 10 mm dorsal of the midcommissural plane.

Akt and mTORC1 signaling as predictive biomarkers for the EGFR antibody nimotuzumab in glioblastoma

Glioblastoma (GB) is the most frequent primary brain tumor in adults with a dismal prognosis despite aggressive treatment including surgical resection, radiotherapy and chemotherapy with the alkylating agent temozolomide. Thus far, the successful implementation of the concept of targeted therapy where a drug targets a selective alteration in cancer cells was mainly limited to model diseases with identified genetic drivers. One of the most commonly altered oncogenic drivers of GB and therefore plausible therapeutic target is the epidermal growth factor receptor (EGFR). Trials targeting this signaling cascade, however, have been negative, including the phase III OSAG 101-BSA-05 trial. This highlights the need for further patient selection to identify subgroups of GB with true EGFR-dependency. In this retrospective analysis of treatment-naïve samples of the OSAG 101-BSA-05 trial cohort, we identify the EGFR signaling activity markers phosphorylated PRAS40 and phosphorylated ribosomal protein S6 as predictive markers for treatment efficacy of the EGFR-blocking antibody nimotuzumab in MGMT promoter unmethylated GBs. Considering the total trial population irrespective of MGMT status, a clear trend towards a survival benefit from nimotuzumab was already detectable when tumors had above median levels of phosphorylated ribosomal protein S6. These results could constitute a basis for further investigations of nimotuzumab or other EGFR- and downstream signaling inhibitors in selected patient cohorts using the reported criteria as candidate predictive biomarkers.

Best practices for the use of intracerebroventricular drug delivery devices

For decades, intracerebroventricular (ICV), or intraventricular, devices have been used in the treatment of a broad range of pediatric and adult central nervous system (CNS) disorders. Due to the limited permeability of the blood brain barrier, diseases with CNS involvement may require direct administration of drugs into the brain to achieve full therapeutic effect. A recent comprehensive literature review on the clinical use and complications of ICV drug delivery revealed that device-associated complication rates are variable, and may be as high as 33% for non-infectious complications and 27% for infectious complications. The variability in reported safety outcomes may be driven by a lack of consensus on best practices of device use. Numerous studies have demonstrated that employing strict aseptic techniques and following stringent protocols can dramatically reduce complications. Key practices to be considered in facilitating the safe, long-term use of these devices are presented.