OS06.7.A Underlying mechanisms of verbal fluency in glioma patients: language or executive functioning?

Background Glioma patients often suffer from cognitive deficits, such as in language and executive functioning (EF). A sensitive test to identify these deficits is verbal fluency (VF). In VF, participants are asked to generate as many unique words within a given semantic category (category fluency - CF) or starting with a given letter (letter fluency - LF) within one minute. While both language and EF play a role in VF, the relative contribution of both domains remains unclear. We aim to retrospectively investigate performance on VF and, for the first time, on Non-Verbal Fluency (NVF), requiring to connect 5 points in different patterns within three minutes. Additionally, we aim to explore the influence of language and EF on VF performance in glioma patients.

Materials and Methods 69 adults with gliomas in eloquent areas underwent a comprehensive neuropsychological test-battery at 1-2 months before surgery (T1) and 3 (T2) and 12 months (T3) after surgery. The protocol consisted of VF (CF: animals, professions, LF: D-A-T/K-O-M), language tests (Repetition (Akense Afasie Test), Token Test, Boston Naming Test) and EF tests (Five Point Test, Trail Making Test, Stroop Colour-Word Test, Wisconsin Modified Card Sorting Task). VF and NVF performance were compared 1) to healthy population using one sample t-tests/Wilcoxon rank-tests (all patients), and 2) between T1, T2, and T3 with paired sample t-tests/Wilcoxon rank-tests (31 patients). Linear regression analyses were conducted to investigate the predictive value of language and EF on VF for all patients.

Results Preoperatively, patients were impaired on all VF tasks. Especially CF profession performance was more prone to deterioration after surgery at T2 and T3. In contrast, NVF was intact and even improved after surgery (T1-T3, T2-T3). NVF (p = .032, EF) was a predictor for CF animals while the Token Test (p = .023, language) was a predictor for CF professions. Both NVF (p = .032, EF) and the Token Test (p = .004, language) were predictors for LF.

Conclusion First, glioma patients were preoperatively impaired in VF but were preserved in NVF, as is in line with the literature. Secondly, CF professions appeared to be particularly sensitive to detect long-term postoperative decline. Thirdly, the main result of this study is that both language and EF mechanisms appeared to be responsible for VF performance in glioma patients. These findings are useful for interpreting VF impairment in glioma patients and for therapeutic interventions, suggesting a combination of language and EF training materials.

OS10.7.A Localization patterns of language errors during direct electrical brain stimulation: a systematic review

BACKGROUND

Awake craniotomy with direct electrical stimulation (DES) is the standard treatment for patients with eloquent area gliomas. Language errors (paraphasias) are detected with DES and they indicate functional boundaries that need to be maintained to preserve quality of life. However, it is not fully clear in which brain locations paraphasias at different linguistic modalities and levels (production, comprehension, reading, writing, phonology, semantics, syntax) occur.

MATERIALS AND METHODS

A systematic review was conducted. We included 102 studies reporting on specific paraphasias and the corresponding brain locations during awake craniotomy with DES in adult glioma patients.

RESULTS

First, a wide distribution of brain locations for all paraphasias (n=930) was found, but patterns were observed. Cortically, paraphasias occurred most often in the precentral gyrus (22%), while subcortically, they occurred mainly at the inferior fronto-occipital fascicle (IFOF: 10%). Localization patterns for different paraphasia types and the corresponding language functions were also found: production/articulation (n=393)-precentral gyrus (41%), inferior frontal gyrus (9%), frontal aslant/striatal tract (4%), postcentral gyrus (3%); semantics (n=128)-IFOF (57%), superior temporal gyrus (9%); phonology (n=115)-arcuate fascicle (52%), superior longitudinal fascicle (10%), uncinate fascicle (3%); reading (n=25)-temporal lobe (48%), inferior longitudinal fascicle (32%); syntax (n=15)-inferior frontal gyrus (27%); speech initiation (n=9)-supplementary motor area (33%), frontal aslant tract (22%), frontal striatal tract (22%); writing (n=7)-superior parietal gyrus (71%). Second, 59% of all paraphasias occurred cortically, 40% subcortically and 1% at both levels.

CONCLUSION

The localization of most paraphasias are consistent with the assumed functionality of those brain locations as presented in the Dutch Linguistic Intraoperative Protocol model. However, new locations for production/articulation, phonology, reading and writing were found. This needs to be taken into consideration for future selection of pre, intra and postoperative language tasks at different language modalities and levels. Additionally, DES should always be applied at the subcortical level as a standard addition to the routine cortical mapping during awake craniotomy. In conclusion, this is the first systematic review on the localization of specific paraphasias during awake craniotomy. Based on the identified language localization patterns, language tasks could be selected more accurately. This could guide, and perhaps improve, pre, intra and postoperative language testing and monitoring, which in turn, may pave the way to a better postoperative language outcome. The possible relation between different intraoperative paraphasias and language outcome has yet to be determined.

OS10.3.A Predicting delirium after craniotomy in neuro-oncology

BACKGROUND

Post-operative delirium (POD) is a frequent and severe complication after neurosurgical operations. Good prediction of POD after craniotomy in neuro-oncologic patients is important to install prophylactic measures, increase recognition and apply early treatment. Hence, we compared logistic regression with machine learning to build an accurate predictive model in a large dataset.

MATERIAL AND METHODS

POD was defined in case of a Delirium Observation Scale (DOS) ≥ 3 or start of antipsychotic treatment for delirium within 10 days after surgery. Adult patients undergoing a craniotomy for a neuro-oncologic disease in the Erasmus Medical Centre in Rotterdam were retrospectively included. The cohort was split into a training (75%), after three-fold cross validation, and test set (25%). Logistic regression and Lasso Elastic-Net Regularized Generalized Linear Models (GLMNet) were trained based on 19 pre- and intra-operative features and risk factors were identified based on the superior model.

RESULTS

We included 1025 neuro-oncologic craniotomies between June 2017 and September 2020. Overall incidence of POD was 18.6% (95%CI 17.4–19.8). Compared to logistic regression, Lasso GLMNet performed superior (AUC 0.73 vs. 0.76) based on the optimal tuning parameters (α=1, λ=0.014). Several non-modifiable risk factors such as age (OR1.01), prior delirium (OR1.04), memory problems (OR1.12), surgery duration (OR1.01) and modifiable risk factors, such as low potassium (OR0.97) levels and opioid administration (OR1.03), were identified.

CONCLUSION

POD is a frequent complication after craniotomy in neuro-oncologic patients. Lasso GLMNet was useful in predicting POD in this cohort. Validation in a prospective cohort of this model should be applied to further evaluate its value in diminishing POD.

P11.27 Drug screening of available anti-cancer drugs on patient-derived GBM cultures identifies candidate treatments for a subpopulation of GBM patients

BACKGROUND

The development of new therapeutic agents generally takes many years to translate to clinically-effective new treatments. Among the strategies to reduce this time frame, efforts are now being undertaken to investigate drug repurposing. With this approach, compounds available for a specific disease are evaluated for their therapeutic efficacy in other diseases. We have set up a patient-derived cell culture model to apply this strategy for glioblastoma (GBM).

MATERIAL AND METHODS

Fresh patient-derived tumour tissue was dissociated and cultured in serum-free medium supplemented with EGF and bFGF. MGMT status was determined by methylation-specific PCR.Drug screening was performed using the NIH anti-cancer collection containing 114 approved oncology drugs. Compounds include chemotherapeutic agents as well as small molecule targeted agents. Readout for drug effects is based on ATP-based viability assay. Using systems modelling approaches, integrated analysis of both mutational and expression data of each tumour is applied to identify key pathways involved in response to specific compounds.

RESULTS

Molecular analysis demonstrated that copy number variations are preserved under serum-free culture conditions and that the MGMT methylation status is retained in over 75% of cases. Screening of the NIH anti-cancer collection on 55 GBM cell cultures revealed high intertumoral variation in response to most drugs. This included subsets of GBM revealing exceptionally high sensitivity to specific agents at clinically-feasible concentrations. Further ranking of the compounds was made based on the therapeutic index (IC50 tumour versus normal human astrocytes) and predicted blood-brain-barrier crossing capability. Currently, integrated analysis of molecular profiles of the tumour in relation to the drug response data is ongoing with the aim of identifying response predictors to these clinically-approved anti-cancer agents.

CONCLUSION

Our patient-derived in vitro drug screening assay may offer a tool to identify available anti-cancer agents that are effective in a subpopulation of GBM patients and that may be implemented in future stratified clinical trials for this patient group.

P11.34 Bone Morphogenetic Protein 4 can sensitize glioblastoma cells to temozolomide

BACKGROUND

Glioblastoma (GBM) is the most prevalent and lethal primary brain tumor. Its recurrence and resistance to current therapies, i.e. temozolomide (TMZ), is thought to result from a subpopulation of cells exhibiting stem cell properties, called glioblastoma stem-like cells (GSCs). Bone Morphogenetic Protein 4 (BMP4) induces GSCs differentiation, leading to a less resistant phenotype. In this study we show that co-treatment of BMP4 with TMZ has therapeutic benefit in a subset of GBM cell lines. Furthermore, we looked for patients’ molecular signatures that could predict sensitivity to this combination treatment.

MATERIAL AND METHODS

A panel of 17 primary GBM cultures (passages 5–10) were treated with increasing concentrations of TMZ, BMP4 and TMZ + BMP4 for 5 and 7 days and cell viability has been measured. The Combination Index (CI) of the two drugs was calculated to assess the response of each line to TMZ and BMP4 treatment. DNA was used to determine the MGMT promotor methylation status and for targeted exome sequencing. Expression levels of BMP signaling components and differentiation associated genes were determined by qPCR.

RESULTS

12 cultures of primary GBMs and 5 cultures of recurrent GBMs were included. Overall, 71% of the tested cell lines was resistant to TMZ, while 41% was resistant to BMP4. Strikingly, 53% of primary cultures show synergy between TMZ and BMP4 (CI < 1 at a Fraction Affected of 50% (Fa50)). There was no significant difference in synergy between five or seven days of treatment. However, combination treatment of BMP4 and TMZ was more effective than sequential treatment.

CONCLUSION

Co-treatment of BMP4 and TMZ could be of therapeutic benefit in GBM patients, irrespective of their sensitivity to TMZ. Further research regarding the mechanism behind this synergy is necessary as to identify predictive markers for treatment response.

Identification of novel candidate genes for ependymoma progression in chromosomal regions over-represented at recurrence and detected by CGH array

2008

Background: The biology and genetics of ependymomas remain poorly understood. As opposed to other pediatric tumors, few recurrent chromosomal abnormalities or relevant pathways have been identified. Method: In order to gain new insight into the molecular mechanisms involved in ependymoma progression, we performed BAC array-based comparative genomic hybridization (aCGH) in a series of 59 tumors at diagnosis and at relapse (42 posterior fossa and 17 supratentorial). Specific chromosomal imbalances were confirmed by FISH. Expression of candidate genes was evaluated by RT-PCR and immunohistochemistry. Results: As compared to CGH (Cancer Genet Cytogenet 2002), aCGH detected more abnormalities since 18/33 samples at diagnosis and 22/26 at recurrence showed chromosomal imbalances. Three distinct patterns were observed : no imbalance (15 at diagnosis, 4 at relapse), large and numerous imbalances (7 at diagnosis, 12 at relapse) and small and rare imbalances (11 at diagnosis, 10 at relapse). At diagnosis, absence of chromosomal imbalance was correlated with young age (p=0.034) and shorter progression-free survival (p=0.014). At relapse, patients with large and numerous imbalances had a shorter survival (p=0.026). Specific chromosomal imbalances were significantly more frequent at recurrence: 9 qter gain (54% vs 21%), 1q gain (12% vs 0%) and 6q loss (27% vs 6%). Samples were available both at diagnosis and relapse for 16 patients. Whole genome changes were towards increase of genomic abnormalities (n=10) but also simplification (n=6), the former being associated with a higher risk of death from disease (Fisher exact, p=0.03). A candidate gene strategy was focussed on the frequently gained 9qter locus. Significant overexpression compared to normal brain was identified for Tenascin-C (median 35 fold, max 220 fold, p<0.0001) and Notch1 (median 6 fold, max 45 fold, p<0.0001). Notch pathway analysis by RT-PCR revealed potential regulatory loops between JAG1/2 or DLL1/3 and Notch1/2. Conclusion: aCGH pattern may identify subgroups of ependymomas with respect to prognosis. Notch pathway and Tenascin-C are important regulatory genes in ependymoma progression and may represent interesting new targets for therapy.

No significant financial relationships to disclose.

Human adenovirus type 35 vector for gene therapy of brain cancer: improved transduction and bypass of pre-existing anti-vector immunity in cancer patients

Clinical trials in malignant glioma have demonstrated excellent safety of recombinant adenovirus type 5 (Ad5) but lack of convincing efficacy. The overall low expression levels of the Coxsackie and Adenovirus receptor and the presence of high anti-Ad5-neutralizing antibody (NAb) titers in the human population are considered detrimental for consistency of clinical results. To identify an adenoviral vector better suited to infect primary glioma cells, we tested a library of fiber-chimeric Ad5-based adenoviral vectors on 12 fresh human glioma cell suspensions. Significantly improved marker gene expression was obtained with several Ad5-chimeric vectors, predominantly vectors carrying fiber molecules derived from B-group viruses (Ad11, Ad16, Ad35 and Ad50). We next tested Ad35 sero prevalence in sera derived from 90 Dutch cancer patients including 30 glioma patients and investigated the transduction efficiency of this vector in glioma cell suspensions. Our results demonstrate that the sero prevalence and the titers of NAb against Ad35 are significantly lower than against Ad5. Also, recombinant Ad35 has significantly increased ability to transfer a gene to primary glioma cells compared to Ad5. We thus conclude that Ad35 represents an interesting candidate vector for gene therapy of malignant glioma.

Shunting normal pressure hydrocephalus: the predictive value of combined clinical and CT data

The value of an ordinal global scale derived from combined clinical and CT data (clin/CT scale) to predict the clinical outcome in 112 patients shunted for presumed normal pressure hydrocephalus (NPH) was analysed. The clinical data were retrospectively collected, all CT scans were re-evaluated, and the clin/CT scale was determined blind to the results of further ancillary tests and to the post-surgical outcome. The scale ranked three classes of prediction: on the basis of clinical and CT characteristics, improvement after shunting was probable, possible, or improbable. The predictive value of the clin/CT scale for the subgroup of communicating NPH was established for two different strategies, depending on the strictness of selection criteria for shunting. In the subgroup of patients with presumed communicating NPH, the prevalence of shunt responsiveness was 29%; the best strategy was to shunt only patients with probable shunt-responsive NPH: the sensitivity was 0.54, the specificity 0.84, and the predictive accuracy 0.75, with a limited number of ineffective shunts (11%) and missed improvements (13%). The study illustrates its need to assess the pre-test probability of NPH based on combined clinical and CT data, before establishing the clinical usefulness of an ancillary test.

Normal-pressure hydrocephalus. Is cisternography still useful in selecting patients for a shunt?

The clinical usefulness of cisternography in selecting patients with presumed normal-pressure hydrocephalus for shunting was investigated in 76 patients. The predictive value of a scale based on combined clinical and computed tomographic criteria was first established, followed by an assessment of the predictive value of cisternography. Predictions based on cisternograms were identical to those of the clinical/computed tomographic scale in 43%, better in 24%, and worse in 33%. Our findings suggest that cisternography does not improve the diagnostic accuracy of combined clinical and computed tomographic criteria in patients with presumed normal-pressure hydrocephalus.

Shunting normal-pressure hydrocephalus: do the benefits outweigh the risks? A multicenter study and literature review

We performed a multicenter retrospective study in 166 consecutive patients shunted for presumed normal-pressure hydrocephalus (NPH) in the four neurosurgical departments of Amsterdam. Overall improvement occurred in 36%, substantial improvement in 21%. In the subgroup of idiopathic NPH (N = 127), marked improvement was only 15%. The incidence of shunt-responsive NPH in our area was 2.2/million/year. The rate of severe and moderate shunt-related complications was 28%, leading to death or severe residual morbidity in 7%. The substantial benefit/serious harm ration in the whole group was only three (21%/7%), decreasing to 1.7 in idiopathic NPH. By excluding patients at high surgical risk, this ratio might have risen to 10 in the whole group and to six in idiopathic NPH. Our experience is much less favorable than that encountered in the literature, reporting overall improvement in 74% and marked improvement in 55% of the shunted patients. We conclude that NPH is probably a very rare and still overdiagnosed syndrome and that the overall morbidity rate for each patient demonstrating meaningful improvement is high.

Chronotopographical potential distribution of some SSEP components in cerebrovascular insufficiency

In 7 patients with symptoms of cerebrovascular diseases a somatosensory evoked potential (SSEP) chronotopogram was constructed after median nerve stimulation of seven different EP components: N20, P25, P45, P100, N140, P200 and P300. We examined only a limited number of patients (and controls) because the methodology is very time-consuming. We analyzed the topography in these patients in order to obtain insight in the effect of this disease on EP distributions and to find arguments in favor of the use of this methodology in clinical examination. These chronotopographical maps were constructed on the basis of the localization of maximal amplitude of the different components and their dipole counterparts (if present). 3 patients showed a delay of the specific components, and in 1 patient most of the non-specific components were delayed. The chronotopographical representation in most patients was abnormal. Relations with clinical state and computer tomography (CT) are described. Focal hypodensity on the CT gives rise to a large extension of the area of the specific component N20, overruling the dipole counterpart P20. Slight cortical atrophy in 4 patients causes abnormalities in the P300/N300 dipole direction. Chronotopograms give new information. Therefore, it seems justified to improve the method and implement it for clinical use in the near future.

SSEP chronotopography in patients with multiple sclerosis

In 10 patients with definite MS, an SSEP chronotopogram was constructed of 7 different, well-defined components: N20, P25, P45, P100, N140, P200 and P300. Chronotopographical maps were constructed on the basis of the localization of maximal amplitudes of the different components and their dipolar counterparts (when present). Most patients showed a delay of different specific as well as aspecific components. The chronotopogram was not much different from normal except for P45. Most generators therefore seem to stay stable. One of the P45 dipole generators vanished, probably due to a slight change in its direction, or more probably as a consequence of loss of association fibres in the cortical white matter. Spatio-temporal mapping provides new, clinically relevant information. The development of automatic methods for this mapping is justified for routine clinical use in neurology.