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Tumoural-CD8+T cells exhibit exhausted or dysfunctional states. Contrary to immunotherapy-responsive exhausted-CD8+T cells, the clinical features of dysfunctional-CD8+T cells are disputed. Hence, we conducted large-scale multi-omics and multi-dimensional mapping of CD8+T cell-states across multiple cancer patient-cohorts. This identified tumour-specific continuum of CD8+T cell-states across 6 human cancers, partly imprinted by organ-specific immuno-modulatory niches. Herein, melanoma and glioblastoma enriched prototypical exhausted (CD8+TEXT) and severely-dysfunctional (CD8+TSDF) states, respectively. Contrary to CD8+TEXT, CD8+TSDF displayed transcriptomic and epigenetic effector/cytolytic dysfunctions, and dysregulated effector/memory single-cell trajectories, culminating into maladaptive prodeath stress and cell-cycle defects. Suboptimal antigen-priming underscored CD8+TSDF, which was distinct from immune-checkpoints “rich” CD8+TEXT, reflecting chronic antigen-stimulation. Continuum variation also existed on tumour spatial-level, with convergent (CD8+TEXT-supportive vascular regions) and divergent features (dysfunctional CD4+T::CD8+TSDFcell-to-cell interactions) between melanoma and glioblastoma. Globally, IFNγ-IL2 disparities, paucity of intra-tumoural CD4+/CD8+T cells, and myeloid TGFβ/wound healing responses, distinguished CD8+TSDF-landscape. Within immuno-oncology clinical-trials, anti-PD1 immunotherapy failed to “reinvigorate” CD8+TSDF-landscape, and instead facilitated effector-dysfunction and TGFβ/wound healing. However, cellular immunotherapies (dendritic cell-vaccines, adoptive T-cell therapy) ameliorated assorted CD8+TSDF-landscape disparities, highlighting a roadmap for anti-glioblastoma multimodal-immunotherapy. Collectively, our study comprehensively expands clinical-knowledge on CD8+T cell-exhaustion and suggests that tumour-specific, pre-existing CD8+TEXT/TSDF-states, determine immunotherapy-responses.

SLIT2 is a secreted polypeptide that guides migration of cells expressing ROBO1&2 receptors. Herein, we investigated SLIT2/ROBO signaling effects in gliomas. In patients with glioblastoma (GBM), SLIT2 expression increased with malignant progression and correlated with poor survival and immunosuppression. Knockdown of SLIT2 in mouse glioma cells and patient derived GBM xenografts reduced tumor growth and synergized with immunotherapy to prolong survival. Tumor cell SLIT2 knockdown inhibited macrophage invasion and promoted a cytotoxic gene expression profile, which improved tumor vessel function and enhanced efficacy of chemotherapy and immunotherapy. Mechanistically, SLIT2 promoted microglia/macrophage chemotaxis and tumor-supportive polarization via ROBO1&2-mediated PI3Kγ activation. Macrophage Robo1&2 deletion and systemic SLIT2 trap delivery mimicked SLIT2 knockdown effects on tumor growth and the tumor microenvironment (TME), revealing SLIT2 signaling through macrophage ROBOs as a novel regulator of the GBM microenvironment and a potential immunotherapeutic target for brain tumors.

Background Long-term survival can be achieved in an increasing number of glioma patients after treatment. Therefore, safeguarding these survivors’ quality of life (QoL) is essential. Neurocognitive decline arises in many young patients, placing a heavy burden on the social and economic aspects of the patients’ lives. A lot of debate is currently ongoing regarding the prevalence of neurocognitive impairment and individual predictors of whom is susceptible for such side effect. Material and Methods In this cross-sectional study, 37 WHO grade 2-3 adult glioma survivors, at least one year after multimodal therapy, were tested using a comprehensive neurocognitive test battery covering multiple cognitive domains. Neurocognitive test scores were converted into z-scores using country-specific normative data. Cognitive impairment was defined as a z-score lower or equal to -1.50 for each subtest. Age, time since multimodal therapy, radiotherapy treatment and tumour location were included as predictors in a linear regression model per outcome (n=12). Results In this cohort, 29 patients (78%) showed a test score below the predefined cutoff on at least one cognitive test. The percentage of patients who showed test-specific cognitive impairment ranged from 8.1% to 56.76% per test. Fine motor skills, verbal memory, processing speed and executive functioning were the most commonly affected cognitive domains. In this study, the variability in processing speed performance was associated with age (TMT A, p=0.03), time since therapy (WAIS-IV coding, p=0.02) and tumour location. In these measures, poorer outcomes were observed with increasing age, longer time since therapy and in patients with gliomas located in the left frontal lobe. Moreover, age showed to be a significant predictor of verbal memory, with poorer outcomes on the HVLT-R delayed recall task with increasing age (p=0.04). Tumour location predicted working memory performance, as patients with right parietal tumours (p=0.03) showed significantly worse on the WAIS-IV digit span task. Conclusion These preliminary data underline the various alterations of neurocognitive functioning in glioma survivors after multimodal therapy. Therefore, future research needs to shift towards a patient-tailored approach. The next step in this study will be to link these neurocognitive data to advanced neuroimaging data to explore the potential predictive value of imaging markers for neural damage and cognitive outcomes, paving the path to innovative treatment planning techniques.

Background Glioblastoma Multiforme (GBM) remains the most common malignant primary brain tumor with a dismal prognosis that rarely exceeds beyond two years despite extensive therapy, which consists of maximal safe surgical resection, radiotherapy and/or chemotherapy. Recently, it has become clear that GBM is not one homogeneous entity and that both intra-and intertumoral heterogeneity contribute significantly to differences in tumoral behavior which may consequently be responsible for differences in survival. Strikingly and in spite of its dismal prognosis, small fractions of GBM patients seem to display extended survival compared to the large majority of patients. The underlying mechanisms for this peculiarity remain largely unknown however, even though emerging data suggest that both cancer cell-autonomous and microenvironmental factors and their interplay probably play an important role. Material and Methods We used high-dimensional, multiplexed immunohistochemistry to spatially, and cytometry by time-of-flight to quantitively characterize the cell constitution and interactions within the tumor microenvironment (TME) in 21 extreme long-term survivors (living over ten years since primary diagnosis or five years after recurrence) and 42 deeply matched short-term controls (living under 1.5 year) on a single cell level. For all tumors (epi-)genetic data was also collected. Results We identified a high level of both inter-and intrapatient heterogeneity defined by several distinct tumor niches, as well as described interactions within these niches and with the surrounding infiltrating immune cells of the TME. By linking patient characteristics with the heterogeneous immune composition we are building an immune stratification that can be linked to patient survival in GBM. Conclusion Generating an immune stratification for GBM will allow us to identify immune characteristics responsible for longer or even exceptional survival, as well as thoroughly identify tumor components that may serve as a potential target for personalized treatment strategies. Therefore, this study is also an essential initial step towards such clinical trials which alter the TME in a favorable way with a personalized modulation strategy.

Background The objective of this study is to cross-check the ICD-O-3 topography and morphology codes of registered glioma patients with findings in their pathology reports and to investigate the integration of relevant molecular markers in the final histopathological diagnosis. Materials and methods Since information regarding molecular tests and corresponding conclusions are not available as structured data at the Belgian population level a manual screening of all pseudonymized full text pathology reports available at the Belgian Cancer Registry (BCR) for adult glioma patients diagnosed between 2017 and 2019 was conducted. ICD-O-3 morphology and topography codes from the BCR database (provided by the hospital oncological care programs and laboratories for histopathology), were cross-checked with the data from the pathology reports. Relevant molecular markers were manually extracted from the pathology reports of confirmed glial tumors. The final diagnosis as mentioned in the reports and the integration of the appropriate molecular markers were checked against the WHO 2016 classification. Results For 1.892 of 2.379 registered gliomas (73%), a specific topographic code was provided. For 8% of patients registered with code C71.9 (unspecified region of the brain), a change to a specific topography code was implemented based on details in the pathology reports. For only 98 of 2.186 patients (4,5%) with available pathology reports, the ICD-O-3 morphology code was adjusted based on the information in the pathology reports. For 59 patients this was a change of grade within the same tumor group. In the subgroup of patients with astrocytic tumors, for 314 of 1.887 patients (16,6%) the IDH status (IDH1-IHC or IDH1/2-NGS) was not identifiable in the available reports. For only 1.091 of 1.887 patients (57,8%) the reports provided an integrated diagnosis including molecular findings, while for the other reports the tumor was not specified (NOS) in the conclusion. For 1.309 of 1.887 patients (69,4%), the final diagnosis in the pathology reports was compatible with the molecular markers. For 553 (29%) patients this was not the case because the relevant molecular markers were not integrated in the conclusion although available (i.e. in the conclusion of these pathology reports the tumor was NOS, but details of the molecular test result were however available somewhere in the reports). Conclusion Morphology codes of registered glioma are largely in line with findings in the pathology reports. The use of specific ICD-O-3 topography codes should be further encouraged and also molecular testing and the use of the integrated diagnosis in the pathology reports can be improved. These findings will be further processed and incorporated in the ongoing Quality Indicator project for glioma in Belgium and will be used to develop strategies to further optimize the reporting of these tumors towards the BCR.

BACKGROUND Quality Indicators (QIs) are important tools to assess the quality and variability of oncological care. However, their application in neuro-oncology is limited. The objective of this study was to develop a set of QIs for glioma, covering process and outcome indicators. METHODS First a systematic literature search was performed in peer-reviewed papers and grey literature to identify existing QIs in neuro-oncology and guidelines or recommendations that could be translated into new QIs. The PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) checklist and flow diagram were taken into account. The search strategy focused on diagnostics, treatment, follow-up and survival. For each (set of similar) recommendation(s) a QI was created that could easily be translated into a measurable proportion. Concordant QIs were rationalized to further reduce redundancy. Secondly a two round Delphi survey was organized amongst a multidisciplinary expert panel that was asked to score relevance for all proposed QIs. The panel consisted of neurosurgeons(4), radiation(3) and medical(3) oncologists, pathologists(3), radiologists(2), neurologists(1), nuclear medicine physicians(2) from university and non-university centers, and representatives of the Belgian Cancer Registry. RESULTS The conducted literature search in PubMed and Embase yielded 2392 abstracts. After screening and duplicate removal, 221 full text articles were assessed of which 79 were retained. In addition 28 references from the Grey literature were added. In total 240 recommendations and 30 QIs could be identified in this way. After translation of these recommendations into a measurable proportion, merging with the QIs found as such in the literature and rationalization, 148 QIs were presented to the expert panel. In the Delphi survey 15 of the 19 (79%) invited experts responded and eventually consensus was reached on 46 QIs that were considered relevant for the assessment of 6 different domains of neuro-oncological care: diagnosis and imaging (10), surgery (4), pathology (6), radio/chemotherapy (14), recurrence (5) and supportive treatment (7). CONCLUSION A set of 46 QIs grouped in 6 categories to assess the quality of care of glioma patients was developed. These QI’s are readily applicable dependent on the availability of population-based health care data

Background and purpose Pseudoprogression is a frequent phenomenon observed since the introduction of postoperative therapy with radiotherapy and temozolomide (RT/TMZ) in glioblastoma multiforme (GBM) patients. However, the criteria defining pseudoprogression, its incidence, the time of occurrence and its impact on therapy and outcome remain poorly defined. Methods The objective of this study is to compare two sets of criteria (liberal and stringent), defining pseudoprogression, in a cohort of patients treated before and after the introduction of RT/TMZ in the standard postoperative treatment. This retrospective review includes 136 unselected and consecutively treated patients with pathologically diagnosed GBM. Results Pseudoprogression was observed in 10 (12%) cases applying the stringent criteria, and in 18 (23%) patients when using the liberal criteria, in the cohort treated with RT/TMZ. Pseudoprogression was observed in only one patient treated with RT alone. The median time to pseudoprogression was 4 weeks after the end of RT. Patients with pseudoprogression had a median survival time of 28 months, compared with 12 months for patients without pseudoprogression. Conclusions The incidence of pseudoprogression after RT/TMZ strongly depends on the applied criteria. However, regardless of the stringency of the criteria, the impact on survival remains the same.

Patients with relapsed malignant glioma have a poor prognosis. We developed a strategy of vaccination using autologous mature dendritic cells loaded with autologous tumour homogenate. In total, 12 patients with a median age of 36 years (range: 11-78) were treated. All had relapsing malignant glioma. After surgery, vaccines were given at weeks 1 and 3, and later every 4 weeks. A median of 5 (range: 2-7) vaccines was given. There were no serious adverse events except in one patient with gross residual tumour prior to vaccination, who repetitively developed vaccine-related peritumoral oedema. Minor toxicities were recorded in four out of 12 patients. In six patients with postoperative residual tumour, vaccination induced one stable disease during 8 weeks, and one partial response. Two of six patients with complete resection are in CCR for 3 years. Tumour vaccination for patients with relapsed malignant glioma is feasible and likely beneficial for patients with minimal residual tumour burden.

Introduction and Aim: Glioblastoma Multiforme is a WHO grade IV neoplasm and is the most frequent primary brain tumor in adults. In spite of current multimodal treatment the prognosis remains poor, with a median overall survival of 14.6 months and a mortality rate of 88% within 3 years. At time of relapse (which is universal), the prognosis is particularly dismal with reports of 100% mortality within 1.5 years. In view of these discouraging results, (pre)clinical research is focused on long-term and tumor-specific treatments, such as oncolytic virotherapy. Not only do oncolytic viruses have the potential to lower tumor volume and viability considerably, they might also alter the local microenvironment within the tumor, to subsequently induce a better immune control through immunotherapeutic approaches. Here we investigate the efficacy of the oncolytic Reovirus Type 3 Dearing, Parvovirus H-1 and Newcastle disease virus (NDV) Hitchner B1 strains in the orthotopic murine GL261 glioma model. Materials and Methods: monolayers of GL261 cells and healthy astrocytes were inoculated with Reovirus, Parvovirus or NDV at different multiplicities of infection, ranging from 0,05 to 10 plague forming units/cells. 72 hours later, cell death was measured via MTT assays. C57/BL6 and Rag2-/- mice were challenged with GL261 cells orthotopically and treated intratumorally with NDV on day 3 or day 7 after tumor induction. Animals were followed for symptoms and survival. Long-term surviving animals were rechallenged with GL261 cells after 100 days. Results: We demonstrated in vitro that Reovirus, Parvovirus and NDV exhibit strong cytotoxicity towards the GL261 cell line. In vivo we showed that local injection of NDV was feasible and significantly prolonged survival of treated animals versus untreated controls. Furthermore, 45% of treated animals survived long-term versus none in the control group. Similar survival data were obtained whether NDV was injected at time of minimal disease or at time of bulky tumor. Tumor rechallenge in long-term surviving animals resulted in 80% survival, suggesting immunization in most mice after NDV therapy. In immunodeficient Rag2-/- animals, NDV failed to prolong survival after glioma challenge, further substantiating the notion that the anticancer effects of NDV can be tracked not only to direct viral oncolysis, but also to an additional immune component. Conclusion: For the first time, we describe that NDV has therapeutic activity against GL261 tumor cells, evidenced in an orthotopic mouse model. NDV therapy significantly improves median survival and induces an antitumor memory response in treated animals. This is a highly innovative finding and ongoing work is focused on further elucidating the immune component in successful oncolytic virotherapy. Furthermore, this model will allow us to study the potential synergism between NDV therapy and dendritic cell mediated immunotherapy, which thus far has not been studied in the field of glioma research

Since many decades, medical doctors and researchers have been intrigued by the possible beneficial contribution of the immune system in the long-lasting combat against cancer. Both in the cellular and humoral immunity arms, powerful tools are available to target the cancer cell. Moreover, the gradual shift of a focus on aspecific reinforcement of the innate immune system towards a specifically activated adaptive immunity in order to reject cancer cells has dominated the field of the last 10 to 20 years(1). Restorative immunotherapy in which cytokine balances are restored or reset and aspecific adoptive immunotherapy using e.g. natural killer (NK) cells or lymphokine-activated killer (LAK) cells are classical representations of the first wave. Specific adoptive immunotherapy using ex vivo activated antitumor cytotoxic T cells and especially active specific immunotherapy (‘cancer vaccines’) are representative for the second wave. Thorough changes in the underlying basic immunology mechanism guide these novel approaches. To date, only the different variants of cancer vaccines are able to induce an immunological memory, as such being the only approach potentially protecting the patients for future cancer re-challenges(2). A perceived low rate of classical objective responses, restricted to volume changes of a measurable tumor burden, has been the principal body of criticism against these therapies. Several new insights however, especially focusing on changes in the micro-environment of the tumors, are only starting to be unraveled. Without any doubt, they’re already now revealing much more than the previous tips of the curtains. Nowadays, converging evidence is being gained in a rapid way, for the need to move towards a third wave of immunotherapy approaches, those of the multimodal integrated immunotherapy paradigms, considering all the relevant players in the complex field of tumor immunology.

Intracranial haemorrhage (ICH) is a rare but potentially devastating complication of oral anticoagulants (OAC). This raises the difficult clinical choice between either permanent cessation of OAC, or continuing OAC and if so, when to restart. To make this choice, one needs to balance the thrombo-embolic risk after cessation of OAC against the risk of recurrent intracranial haemorrhage when OAC are restarted. There are few published data to base this difficult clinical decision on.We present an observational study of a consecutive series of 108 patients, collected prospectively and admitted to our department, with an OAC-related intracranial haemorrhage, in whom we assessed the thrombotic event rate and the recurrent intracranial bleeding rate during follow-up.In the 25 patients in whom OAC were reinstituted no new thrombo-embolic events occurred (0/506 unprotected patient-days). In the group of patients in whom OAC were not restarted (n = 81), the thrombo-embolic event rate was 8/11590 unprotected patient-days, of which only 2 were cerebrovascular thrombo-embolisms. The overall risk of a thrombo-embolic complication can be estimated to be 0.66 events/1000 patient-days at risk (95% exact confidence limits of 0.3 to 1.3 events/1000 patient-days at risk). In three patients the thrombo-embolic event was fatal. We saw recurrent intracranial bleeding in eight patients, 2 of which were fatal. Seven of these occurred before the restarting of the OAC.In OAC-related intracranial haemorrhages, OAC can be stopped safely for a considerable period, with a very low overall thrombotic event rate. The recurrent bleeding risk after restarting OAC is low. Recurrent bleeding mostly occurred before restarting OAC and is probably caused by insufficient or unsustained correction of the initial coagulation deficit. Immediate reversal of anticoagulation provides the patient with the best possible treatment options including surgery. OAC-related intracranial haemorrhages can therefore be actively treated.

CASE REPORT: We report the case of a 38-year-old man with an atypical presentation of LDD. He presented with a sudden amnesia and disorientation in time and space.Neurologic examinationwasnormal. ACT scanof the brain was performed revealing a large hypodens lesion involving the right cerebellarhemisphere.Therewasmoderatemass effect.Magnetic resonance imaging of the brain was performed showing a striated well-defined lesion. The mass was hypointens on T1 weighted imaging and hyperintens on T2 weighted imaging. The diagnosis of LDD was made and a neurosurgical follow-up was installed. A cardiovascular work-up to exclude TIA as an explanation for his symptoms didn’t reveal any relevant finding.

2053 Background: Glioblastoma multiforme (GBM) is a highly malignant, and the most common primary tumor of the central nervous system. Hypermethylation of MGMT promoter region can silence its expre...