Medulloblastoma in adults: evaluation of the Dutch society for neuro-oncology treatment protocol

PURPOSE

Medulloblastoma is a rare tumor in adults. The objective of this nationwide, multicenter study was to evaluate the toxicity and efficacy of the Dutch treatment protocol for adult medulloblastoma patients.

METHODS

Adult medulloblastoma patients diagnosed between 2010 and 2018 were identified in the Dutch rare tumors registry or nationwide pathology database. Patients with intention to treat according to the national treatment protocol were included. Risk stratification was performed based on residual disease, histological subtype and extent of disease. All patients received postoperative radiotherapy [craniospinal axis 36 Gy/fossa posterior boost 19.8 Gy (14.4 Gy in case of metastases)]. High-risk patients received additional neoadjuvant (carboplatin-etoposide), concomitant (vincristine) and adjuvant chemotherapy (carboplatin-vincristine-cyclophosphamide) as far as feasible by toxicity. Methylation profiling, and additional next-generation sequencing in case of SHH-activated medulloblastomas, were performed.

RESULTS

Forty-seven medulloblastoma patients were identified, of whom 32 were treated according to the protocol. Clinical information and tumor material was available for 28 and 20 patients, respectively. The histological variants were mainly classic (43%) and desmoplastic medulloblastoma (36%). Sixteen patients (57%) were considered standard-risk and 60% were SHH-activated medulloblastomas. Considerable treatment reductions and delays in treatment occurred due to especially hematological and neurotoxicity. Only one high-risk patient could complete all chemotherapy courses. 5-years progression-free survival (PFS) and overall survival (OS) for standard-risk patients appeared worse than for high-risk patients (PFS 69% vs. 90%, OS 81% vs. 90% respectively), although this wasn't statistically significant.

CONCLUSION

Combined chemo-radiotherapy is a toxic regimen for adult medulloblastoma patients that may result in improved survival.

Identification, validation and biological characterisation of novel glioblastoma tumour microenvironment subtypes: implications for precision immunotherapy

BACKGROUND

New precision medicine therapies are urgently required for glioblastoma (GBM). However, to date, efforts to subtype patients based on molecular profiles have failed to direct treatment strategies. We hypothesised that interrogation of the GBM tumour microenvironment (TME) and identification of novel TME-specific subtypes could inform new precision immunotherapy treatment strategies.

MATERIALS AND METHODS

A refined and validated microenvironment cell population (MCP) counter method was applied to >800 GBM patient tumours (GBM-MCP-counter). Specifically, partition around medoids (PAM) clustering of GBM-MCP-counter scores in the GLIOTRAIN discovery cohort identified three novel patient clusters, uniquely characterised by TME composition, functional orientation markers and immune checkpoint proteins. Validation was carried out in three independent GBM-RNA-seq datasets. Neoantigen, mutational and gene ontology analysis identified mutations and uniquely altered pathways across subtypes. The longitudinal Glioma Longitudinal AnalySiS (GLASS) cohort and three immunotherapy clinical trial cohorts [treatment with neoadjuvant/adjuvant anti-programmed cell death protein 1 (PD-1) or PSVRIPO] were further interrogated to assess subtype alterations between primary and recurrent tumours and to assess the utility of TME classifiers as immunotherapy biomarkers.

RESULTS

TME^High tumours (30%) displayed elevated lymphocyte, myeloid cell immune checkpoint, programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 transcripts. TME^High/mesenchymal+ patients featured tertiary lymphoid structures. TME^Med (46%) tumours were enriched for endothelial cell gene expression profiles and displayed heterogeneous immune populations. TME^Low (24%) tumours were manifest as an 'immune-desert' group. TME subtype transitions upon recurrence were identified in the longitudinal GLASS cohort. Assessment of GBM immunotherapy trial datasets revealed that TME^High patients receiving neoadjuvant anti-PD-1 had significantly increased overall survival (P = 0.04). Moreover, TME^High patients treated with adjuvant anti-PD-1 or oncolytic virus (PVSRIPO) showed a trend towards improved survival.

CONCLUSIONS

We have established a novel TME-based classification system for application in intracranial malignancies. TME subtypes represent canonical 'termini a quo' (starting points) to support an improved precision immunotherapy treatment approach.

The value of prognostic and predictive parameters in early-stage lung adenocarcinomas: A comparison between biopsies and resections

INTRODUCTION

Since lung adenocarcinoma (LUAD) biopsies are usually small, it is questionable if their prognostic and predictive information is comparable to what is offered by large resection specimens. This study compares LUAD biopsies and resection specimens for their ability to provide prognostic and predictive parameters.

METHODS

We selected 187 biopsy specimens with stage I and II LUAD. In 123 cases, subsequent resection specimens were also available. All specimens were evaluated for growth pattern, nuclear grade, fibrosis, inflammation, and genomic alterations. Findings were compared using non-parametric testing for categorical variables. Model performance was assessed using the area under the curve for both biopsies and resection specimens, and overall (OS) and disease-free survival (DFS) was calculated.

RESULTS

The overall growth pattern concordance between biopsies and resections was 73.9%. The dominant growth pattern correlated with OS and DFS in resected adenocarcinomas and for high-grade growth pattern in biopsies. Multivariate analysis of biopsy specimens revealed that T2-tumors, N1-status, KRAS mutations and a lack of other driver mutations were associated with poorer survival. Model performance using clinical, histological and genetic data from biopsy specimens for predicting OS and DSF demonstrated an AUC of 0.72 and 0.69, respectively.

CONCLUSIONS

Our data demonstrated the prognostic relevance of a high-grade growth pattern in biopsy specimens of LUAD. Combining clinical, histological and genetic information in one model demonstrated a suboptimal performance for DFS prediction and good performance for OS prediction. However, for daily practice, more robust (bio)markers are required to predict prognosis and stratify patients for therapy and follow-up.

P05.04.A Disconcordance between different molecular methods to assess homozygous deletion of theCDKN2A/B locus in IDH-mutant astrocytomas

Background

The fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS 5), includes molecular parameters for both diagnosis and grading in addition to histological features. For IDH-mutant astrocytoma, homozygous deletion (HD) of CDKN2A/B now results in WHO grade 4, even in the absence of microvascular proliferation or necrosis. CDKN2A/B deletions can be determined by various techniques including shallow and targeted sequencing, and using genome wide DNA-methylation arrays. Various algorithms to call deletions also exist for each platform. Concordance between the various techniques and algorithms is however unknown. Because of the importance to properly call CDKN2A/B deletions, we compared two techniques to call HD in IDH-mutant astrocytoma patients.

Methods

Samples from 110 IDH-mutant astrocytoma patients enrolled in the GLASS-NL study, and therefore samples from at least two surgical resections per patient, were available. Overall survival (OS) was measured from date of first surgery.

Both DNA-methylation data and shallow whole-genome sequencing (sWGS) was collected from 219 samples from 101 patients. For DNA-methylation analysis, HD of CDKN2A/B was defined by <-0.6 log2 intensity combined with visual assessment on samples with log2 intensity between -0.6 and -0.2 (method 1), or by using a hard cutoff of <-0.415 log2 intensity, as determined by Shirahata et al. (method 2). Absolute copy number profiles were estimated by ACE from sWGS data, HD of CDKN2A/B was defined by a loss of at least 1.2 CDKN2A alleles (method 3). Agreement score and Cohen’s kappa (κ) as an index for interrater agreement was calculated.

Results

Method 1 and method 2 called an HD of CDKN2A/B in 39 and 33 cases, respectively; method 1 called an HD of CDKN2A/B in 9 cases in which method 2 did not detect an alteration. The agreement was strong with 95% agreement and κ = 0.842.

Method 3 called an HD of CDKN2A/B in 45 cases of which 12 and 19 were not detected by method 1 and method 2 respectively. Method 3 showed an almost perfect level of agreement with method 1, with 97% agreement and κ = 0.911, and a moderate agreement with method 2, with 89% agreement and κ = 0.671.

Survival analysis showed that there was no significant difference in survival when patients were stratified by CDKN2A/B status of the initial sample of all methods. However, when stratified by CDKN2A/B status of the first recurrence, all methods showed a stronger association with OS (method 1: p = 0.001, HR = 2.61[1.44-4.72]; method 2: p = 0.0024, HR = 2.34[1.33-4.11]; method 3: p = 0.0099, HR = 2.34[1.2-4.55]).

Conclusion

Different methods and different cutoffs to determine the presence of a HD in CDKN2A/B may result in different test outcomes. Quality of the DNA, tumor cell percentage of the sample and ploidy are likely to influence the call of homozygous CDKN2A/B deletion. Ring tests are recommended to improve reliability.

OS08.1.A Integrative molecular analysis of matched primary and recurrent IDH-mutant astrocytoma; an update from the GLASS-NL consortium

Background

The evolutionary processes that drive tumor progression in patients with IDH-mutant astrocytoma remain largely unclear. The GLASS-NL consortium was initiated to gain insight into the molecular mechanisms underlying glioma evolution and to identify markers of progression in IDH-mutant astrocytomas. Ultimately, such markers can assist clinical decision making. Here, we present the DNA methylation profiling, RNA-sequencing and shallow whole-genome sequencing (sWGS) of samples included in the GLASS-NL study.

Methods

Eligible were patients with an IDH-mutant, 1p19q non-codeleted, astrocytoma at first diagnosis who underwent surgical resection of the tumor at least twice separated by >6 months, and of whom paired tumor samples were available for analyses. Overall survival (OS) was measured from date of initial surgery.

DNA methylation profiling was performed with the 850kEPIC array, and transcriptome and sWGS by NGS. After quality control, DNA methylation data of 103, expression data of 91, and sWGS data of 92 patients was available for further analysis. Methylation classes were determined according to Capper et al. and copy number alterations (CNAs) were extracted from both sWGS and DNA-methylation data.

Results

110 patients were identified from various medical centers in the Netherlands. The median time between surgical resections was 41.9 months (IQR:26.5-65.9) and after initial surgery, 63% and 22% of the patients were treated with radiotherapy or chemotherapy respectively. The proportion of samples assigned to the high grade methylation class increased ~three-fold at recurrence. 83% of patients that progressed from low to high grade, received treatment prior to recurrent surgery, as compared to 53% of the patients that remained low grade.

Genome wide DNA methylation levels of recurrent samples were lower than that of initial samples. This difference is explained by the increased number of high grades at recurrence, since near identical DNA methylation levels were observed in samples that remained low grade.

Analysis of CNAs revealed chromosomal arms that were more frequently altered in high grade samples. Univariate analysis showed that losses in 3p, 9p, 10q, 13q and 14q were associated with poor OS.

More than 800 differentially expressed genes between initial and recurrent tumor samples were found. Chromosomal enrichment analysis revealed a locus on chromosome 6 enriched with histone genes, to be significantly up-regulated over time.

Conclusion

Longitudinal methylation profiling of IDH-mutant astrocytoma reveals a shift towards a higher grade at tumor recurrence coinciding with reduced DNA methylation levels, and increased frequency of CNAs. Longitudinal expression analysis showed changes in expression of >800 genes, including an up-regulated locus enriched with histone genes. Further integrative analyses are ongoing and will be reported at the meeting.

P11.69.B IDH1/2wildtype gliomas grade 2 and 3 with molecular glioblastoma-like profile have a distinct course of epilepsy compared toIDH1/2wildtype glioblastomas

Background

IDH1/2 wildtype (IDHwt) glioma WHO grade 2 and 3 patients with pTERT mutation and/or EGFR amplification and/or +7/−10 chromosome gain/loss have a similar overall survival time as IDHwt glioblastoma patients, and are both considered glioblastoma IDHwt according to the WHO 2021 classification. However, differences in seizure onset have been observed. This study aimed to compare the course of epilepsy in the two glioblastoma subtypes.

Material and Methods

We analyzed epilepsy data of an existing cohort including IDHwt histologically lower-grade glioma WHO grade 2 and 3 with molecular glioblastoma-like profile (IDHwt hLGG) and IDHwt glioblastoma patients. Primary outcome was the incidence proportion of epilepsy during the disease course. Major secondary outcomes included onset of epilepsy, number of seizure days and antiepileptic drug (AED) polytherapy.

Results

Out of 254 patients, 78% (50/64) IDHwt hLGG and 68% (129/190) IDHwt glioblastoma patients developed epilepsy during the disease course (p=0.121). Epilepsy onset before histopathological diagnosis occurred more frequently in IDHwt hLGG compared to IDHwt glioblastoma patients (90% versus 60%, p<0.001), with a significantly longer median time to diagnosis (3.5 versus 1.3 months, p<0.001). Median total seizure days was also longer for IDHwt hLGG patients (7.0 versus 3.0, p=0.005), and they received more often AED polytherapy (32% versus 17%, p=0.028).

Conclusion

Although the incidence proportion of epilepsy during the entire disease course is similar, IDHwt hLGG patients show a significantly higher incidence of epilepsy before diagnosis and a significantly longer median time between first seizure and diagnosis compared to IDHwt glioblastoma patients, indicating a distinct clinical course.

OS05.5.A Methylation analysis of matched primary and recurrent IDHmt astrocytoma; an update from the Glioma Longitudinal Analysis NL (GLASS-NL) consortium

BACKGROUND

The evolutionary processes that drive progression in patients with IDH-mutant astrocytoma remain unclear. The GLASS-NL consortium, as part of the larger worldwide GLASS consortium, was initiated to gain insight into the molecular mechanisms underlying glioma evolution and to identify markers of progression in IDH-mutant astrocytomas. Such markers can ultimately assist clinical decision making. Here, we present the first results of genome wide methylation profiling of samples included in the GLASS-NL study.

MATERIAL AND METHODS

110 adult patients were identified with an IDH-mutant astrocytoma at first diagnosis. All patients underwent a surgical resection of the tumor at least twice, separated by at least 6 months with a median of 40.9 months (IQR: 24.0, 64.7), in 37% and 18% of the cases, patients were treated with radiotherapy or chemotherapy respectively, before surgical resection of the recurrent tumor. Methylation profiling was done on (macro dissected) DNA isolated of 235 samples from 103 patients (102 1st, 101 2nd, 29 3rd, and 3 4th resection), using the Infinium MethylationEPIC BeadChip array. Copy number variations were also derived from these data. Methylation classes were determined according to Capper et al. (2018). Overall survival (OS) was measured from date of first surgery.

RESULTS

Of all primary tumors, the methylation-classifier assigned 85 (87%) to the A_IDH (‘low grade’) subclass and 10 (10%) to the A_IDH_HG (‘high grade’) subclass. The relative proportion of high grade tumors increased ~three-fold at tumor recurrence (32/101, 32%) and even further in the second recurrence (15/29, 52%). The overall DNA-methylation levels of recurrent samples was lower than that of primary samples. This difference is explained by the increased number of high grade samples at recurrence, since near identical DNA-methylation levels were observed in samples that remained low grade. In an unsupervised analysis, methylation data derived from first and second resections of individual patients mostly (79%) cluster together. This indicates that variability between tumors is larger than temporal heterogeneity within tumors. Recurrent samples that do not cluster with their primary tumor, form a separate cluster and have relatively low genome-wide DNA-methylation.

CONCLUSION

Our data demonstrate that methylation profiling identifies a shift towards a higher grade at tumor progression coinciding with reduced genome-wide DNA-methylation levels.

OS05.2.A MGMT promoter status in IDH1/2 mutant anaplastic astrocytoma patients assessed by DNA methylation profiling and qMS-PCR: a report from the EORTC Brain Tumor Group

BACKGROUND

Temozolomide (TMZ) efficacy in high-grade glioma is related to O 6-methylguanine DNA methyltransferase promoter (MGMTp) methylation. We compared the prognostic and predictive effect of MGMTp between DNA methylation profiling (the MGMT-STP27 model) and quantitative methylation specific polymerase chain reaction (qMS-PCR) in isocitrate dehydrogenase 1 and 2 (IDH1/2) mutant (mt) anaplastic astrocytoma patients.

MATERIAL AND METHODS

The 2x2 factorial design phase III CATNON trial randomized 751 adult patients with newly diagnosed 1p/19q non-codeleted anaplastic glioma to 59.4 Gy radiotherapy (RT), RT with concurrent TMZ, RT with 12 cycles of adjuvant TMZ, or RT with concurrent and adjuvant TMZ. MGMTp methylation status was assessed with the MGMT-STP27 model using 850k EPIC data, and qMS-PCR. IDH1/2 mutation status was determined with a next-generation sequencing panel. Overall survival (OS) was measured from date of randomization.

RESULTS

We identified 444 IDH1/2mt anaplastic astrocytoma patients of which MGMT-STP27 data was available for 440 patients (99.1%), qMS-PCR data for 361 patients (81.3%), and both for 357 patients (80.4%). MGMTp was methylated in 365 patients (83.0%) for the MGMT-STP27 model, and 168 patients (46.5%) for qMS-PCR. The agreement between the MGMT-STP27 model and qMS-PCR is 59.9% with a Cohen’s Kappa score of 0.229. At database lock, 289 patients with MGMT-STP27 data were still alive and 236 patients with qMS-PCR data. The median OS of MGMTp methylated glioma patients was 9.1 yrs [95 % confidence interval (CI) 7.5-not reached] for the MGMT-STP27 model, and not reached [95 % CI 9.1-not reached] for the qMS-PCR data. For MGMTp unmethylated glioma patients, the median OS was 6.9 yrs [95% CI 6.2-not reached] for the MGMT-STP27 model, and 6.8 yrs [95% CI 6.2–9.7] for the qMS-PCR data. The hazard ratio (HR) for OS based on MGMTp methylation was 0.88 [95% CI 0.58–1.31] for the MGMT-STP27 data, and 0.72 [95% CI 0.50–1.03]) for the qMS-PCR data. The HR for OS after RT with any TMZ vs RT alone for the MGMT-STP27 model was 0.53 [95% CI 0.37–0.78] for MGMTp methylated, and 0.54 [95% CI 0.25–1.18] for MGMTp unmethylated glioma patients; and for the MS-PCR data was 0.34 [95% CI 0.19–0.61] for MGMTp methylated, and 0.53 [95% CI 0.33–0.85] for MGMTp unmethylated glioma patients.

CONCLUSION

MGMTp methylation, regardless of assay, was neither prognostic nor predictive for outcome to temozolomide in IDH1/2mt anaplastic astrocytoma patients.

Prognostic significance of genome-wide DNA methylation profiles within the randomised, phase 3, EORTC CATNON trial on non-1p/19q deleted anaplastic glioma

Background

Survival in patients with IDH1/2-mutant (mt) anaplastic astrocytomas is highly variable. We have used the prospective phase 3 CATNON trial to identify molecular factors related to outcome in IDH1/2mt anaplastic astrocytoma patients.

Methods

The CATNON trial randomized 751 adult patients with newly diagnosed 1p/19q non-codeleted anaplastic glioma to 59.4 Gy radiotherapy +/− concurrent and/or adjuvant temozolomide. The presence of necrosis and/or microvascular proliferation was scored at central pathology review. Infinium MethylationEPIC BeadChip arrays were used for genome-wide DNA methylation analysis and the determination of copy number variations (CNV). Two DNA methylation-based tumor classifiers were used for risk stratification. Next-generation sequencing (NGS) was performed using 1 of the 2 glioma-tailored NGS panels. The primary endpoint was overall survival measured from the date of randomization.

Results

Full analysis (genome-wide DNA methylation and NGS) was successfully performed on 654 tumors. Of these, 432 tumors were IDH1/2mt anaplastic astrocytomas. Both epigenetic classifiers identified poor prognosis patients that partially overlapped. A predictive prognostic Cox proportional hazard model identified that independent prognostic factors for IDH1/2mt anaplastic astrocytoma patients included; age, mini-mental state examination score, treatment with concurrent and/or adjuvant temozolomide, the epigenetic classifiers, PDGFRA amplification, CDKN2A/B homozygous deletion, PI3K mutations, and total CNV load. Independent recursive partitioning analysis highlights the importance of these factors for patient prognostication.

Conclusion

Both clinical and molecular factors identify IDH1/2mt anaplastic astrocytoma patients with worse outcome. These results will further refine the current WHO criteria for glioma classification.

OS10.1 Survival analysis of IDH wildtype astrocytomas with molecular features of glioblastoma, WHO grade IV

BACKGROUND

Recently, isocitrate dehydrogenase wildtype (IDHwt) lower grade gliomas (LGGs) that have a telomerase reverse transcriptase (TERT) promoter mutation and/or gain of chromosome 7 combined with loss of chromosome 10 and/or epidermal growth factor receptor amplification have been reclassified as IDHwt astrocytomas with molecular features of glioblastoma, WHO grade IV (‘astrocytomas IDHwt, WHO IV’). Survival of these tumors meeting the criteria of these tumors is less well studied. The objective of this study is to compare the overall survival (OS) between the IDHwt astrocytomas, WHO IV and histological glioblastomas (GBMs).

MATERIAL AND METHODS

In this retrospective multicenter cohort study, all adult patients with a newly diagnosed IDHwt LGG (histologically WHO grade II or III) and with molecular data available were selected from the Erasmus MC and the LUMC from October 2002 to April 2019. LGG patients showing contrast enhancement with necrosis on the MRI at the time of histological diagnosis were excluded. Molecular data were determined using a diagnostic NGS panel. A historical cohort of 195 patients with IDHwt GBMs with molecular data available was used to compare OS. OS was measured from the date of the first diagnostic MR scan.

RESULTS

79 IDHwt LGG patients were identified of which 62 patients had molecular features of glioblastoma (‘astrocytomas IDHwt, WHO IV’), 11 patients did not have these molecular features (‘astrocytomas IDHwt, WHO II & III’). In the remaining 6 patients the molecular data were not conclusive (astrocytomas IDHwt, WHO NOS). Patients with astrocytomas IDHwt, WHO IV were slightly older at diagnosis (median age = 57 years) than patients with GBMs IDHwt in the reference cohort or astrocytomas IDHwt, WHO II & III (respectively: median age 55 years, p=0.032 and 47 years, p=0.035). The relatively young age of our GBM IDHwt cohort reflects more extensive molecular testing in younger patients and histologically lower grade tumors. The median OS of astrocytomas IDHwt, WHO IV (23.8 months) was similar to the median OS of GBMs (19.2 months, log-rank test p=0.37). The median OS in 19 patients with only TERT promoter mutations was 16.8 months, similar to GBMs (p=0.94).

CONCLUSION

There is no statistically significant difference between the OS of IDHwt astrocytomas with molecular features of glioblastoma and the OS of true glioblastomas. Grade II and III IDHwt astrocytoma with molecular features of glioblastoma should be designated WHO grade IV. The presence of TERT promoter mutations alone in this histological context also qualifies for this designation.

PL3.3 Second interim and first molecular analysis of the EORTC randomized phase III intergroup CATNON trial on concurrent and adjuvant temozolomide in anaplastic glioma without 1p/19q codeletion

BACKGROUND

The 1st interim analysis of the CATNON trial showed benefit from adjuvant (adj) temozolomide (TMZ) on overall survival (OS) but remained inconclusive about concurrent (conc) TMZ. A 2nd interim analysis was planned after 356 events.

MATERIAL AND METHODS

The 2x2 factorial design phase III CATNON trial randomized 751 adult patients with newly diagnosed non-codeleted anaplastic glioma to either 59.4 Gy radiotherapy (RT) alone; the same RT with concTMZ; the same RT and 12 cycles of adjTMZ or the same RT with both concTMZ and adjTMZ (doi: 10.1016/S0140-6736(17)31442-3). MGMT promoter methylation (MGMTmeth) status was re-assessed with the Infinium Methylation EPIC Beadchip using the MGMT_STP27 model. Isocitrate dehydrogenase 1 and 2 (IDH) mutation (mt) status was assessed with glioma targeted Agilent SureSelect baits sequence using an Illumina HiSeq2500 Rapid PE100.

RESULTS

With a median follow-up of 56 months and 356 events, the hazard ratio (HR) for OS adjusted for stratification factors after concTMZ was 0.968 (99.1% CI 0.73, 1.28). 5-year OS was 50.2% with and 52.7% without concTMZ (95% CI [44.4, 55.7] and [46.9, 58.1]). An IDHmt was found in 335 of 480 assessed cases (70%). Median OS was 19 mo (95% CI 16.3, 22.3) in IDHwt tumors and 116 mo (95% CI 82.0, 116.6) in IDHmt tumors. The interaction test based on IDH status was significant (p=0.016) in the univariate HR analysis for OS after concTMZ (IDHwt, n=145, events=120, HR = 1.27, 95% CI 0.89, 1.82, p=0.19; IDHmt, n=335, events=92, HR= 0.67, 95% CI 0.44, 1.03, p=0.06). IDHmt was predictive of benefit from adjTMZ (IDHmt HR: 0.41, 95% CI 0.27, 0.64; IDHwt: HR 1.05, 95% CI 0.73, 1.52; interaction test p = 0.001). In IDHmt patients that received adjTMZ, the HR for OS after concTMZ was 0.71 (95% CI 0.35, 1.42, p=0.32). MGMTmeth was found in 288 of 410 assessed cases (70%), interaction test for concTMZ (p = 0.092) and adjTMZ (p = 0.166) did not reach statistical significance.

CONCLUSION

In the entire study cohort, concTMZ did not increase OS. However, in IDHmt tumors a trend towards benefit of concTMZ is present. AdjTMZ increased OS in IDHmt but not in IDHwt tumors. Further analyses and follow-up will allow full assessment of efficacy in the molecular subgroups.

P11.12 Periostin is expressed by pericytes and is crucial for angiogenesis in glioma

BACKGROUND

The expression of the matricellular protein periostin has recently been associated with glioma progression and angiogenesis. The aim of the present study was to identify the cellular source of periostin expression in human gliomas and to study the role of periostin in an in vitro model for angiogenesis.

MATERIAL AND METHODS

The expression of periostin in various types and grades of brain tumors was investigated at the genetics level by RT-PCR and at the protein level by immunohistochemistry. In addition, the expression of periostin in glioma samples was studied by double labeling and in situ RNA techniques. Subsequently, by silencing periostin in a 3D in vitro angiogenesis model, its effects on angiogenesis were studied.

RESULTS

Periostin RNA and protein expression was found to be elevated in pilocytic astrocytoma and glioblastoma, but not in grade II/III astrocytomas. The expression of periostin co-localized with PDGFRβ + cells, but not with Olig2+ / Sox2+ glioma stem cells. Silencing of periostin in pericytes resulted in the attenuation of the number and the length of the vessels, and in decrease in the number of vessel junctions formed.

CONCLUSION

The results prove that pericytes are the main source of periostin in human gliomas. We demonstrate that periostin plays an essential role in the growth and branching of blood vessels. Therefore, periostin and / or its molecular interactions should be explored as a novel target for developing a new anti-angiogenic therapy for glioma.

P11.10 The IFNγ pathway mediates brain metastasis formation of breast cancer

BACKGROUND

In previous work we showed the prominence of the T-cell response in the formation of brain metastases of primary ER negative breast cancers (Mustafa et al, Acta Neuropathol 2018). We also showed that breast cancer cells co-cultured with stimulated T lymphocytes overexpress Guanylate-binding protein 1 (GBP1) accompanying increased trespassing ability through an in vitro blood-brain barrier (BBB) model. In addition, we demonstrated a predilection for metastasizing to brain of breast cancer cells that were co-cultured with activated T cells in a mouse model. We now scrutinize the importance of the IFNγ pathway for tresspassing of the tumor cells through the BBB following T cell contact.

MATERIAL AND METHODS

Anti-hIFN-γ-IgA antibodies were used to neutralize the IFNγ effects on the tumor cells. The effects on the tumor cells is only due to native IFNγ produced by activated T cells, not by recombinant IFNγ. Since the IFNγ expression itself enhances its expression by the T cells, we blocked IFNγ receptors prior to adding CD3+ T cell conditioned media to the breast cancer cells. The receptor blocking was achieved by antibodies to the IFNγα and IFNγβ subunits. Activation of the STAT1 pathway was monitored by GBP1 expression. For functional read-out the in vitro BBB model was used.

RESULTS

The presence of T-lymphocyte-secreted IFNγ in the primary breast cancer microenvironment activates the STAT1-dependent IFNγ pathway in breast cancer cells, endowing them with an increased ability to trespass the in vitro BBB. Moreover, direct inhibition of soluble IFNγ, or blocking of the IFNγ-specific receptor in breast cancer cells significantly decreases their ability to cross the BBB.

CONCLUSION

The results illustrate the specific action of T lymphocytes in the formation of cerebral metastasis involves the IFNγ signaling pathway as one of the crucial entangled pathways Subsequent studies should aim at the interference with the IFNγ pathway to develop preventive strategies against the formation of cerebral metastases of breast cancer.

P11.08 Defining EGFR amplification status for clinical trial inclusion

BACKGROUND

Precision medicine trials targeting the epidermal growth factor receptor (EGFR) in glioblastoma patients require selection for EGFR-amplified tumors. However, there is currently no golden standard in determining the amplification status of EGFR or EGFRvIII expression. Here, we aimed to determine which technique and which cut-offs are suitable to determine EGFR amplification status.

MATERIAL AND METHODS

We compared fluorescent in-situ hybridization (FISH) and RT-qPCR data from patients screened for trial inclusion into the Intellance 2 clinical trial, with data from a panel-based next generation sequencing (NGS) platform (both DNA and RNA).

RESULTS

By using data from >1000 samples, we show which cut-offs are optimal to determine EGFR gene amplification by FISH. Our data also show that gene amplification (as determined by FISH) correlates with EGFR expression levels (as determined by RT-qPCR) with ROC analysis showing an under the curve area of up to 0.902. EGFR expression as assessed by RT-qPCR therefore may function as a surrogate marker for EGFR amplification. Our NGS data shows that EGFR copy numbers can strongly vary between tumors with levels ranging from 2 to more than 100 copies per cell. Levels exceeding 5 gene copies can be used to define EGFR-amplification by NGS; below this level FISH detects very few (if any) EGFR amplified nuclei and none of the samples express EGFRvIII.

CONCLUSION

Our data from central laboratories and diagnostic sequencing facilities, using material from patients eligible for clinical trial inclusion, help defining the optimal cut-off for various techniques to determine EGFR amplification for diagnostic purposes.

P11.11 Circulating Pro-Angiogenic Cells and Proteins in Patients with Glioma and Acute Myocardial Infarction: Differences in Neovascularization between Neoplasia and Tissue Regeneration

BACKGROUND

Although extensive angiogenesis takes place in glial tumors, anti-angiogenic therapies have remained without the expected success. In the peripheral circulation of glioma patients increased numbers of endothelial precursor cells (EPCs) are present, potentially offering targets for anti-angiogenic therapy (Zheng et al., Ann Neurol, 2007). However, for an anti-angiogenic therapy to be successful, the therapy should specifically target glioma-related EPC subsets and secreted factors. Here we compared the EPC subsets and plasma factors in the peripheral circulation of patients with gliomas to acute myocardial infarctions (representing fysiologic regeneration).

MATERIAL AND METHODS

We investigated the five most important EPC subsets and 21 angiogenesis-related plasma factors in peripheral blood samples of 29 patients with glioma, 14 patients with myocardial infarction and 20 healthy people as controls, by an advanced FACS protocol (Huizer et al., PlosOne 2018) and Luminex assay.

RESULTS

In GBM patients all EPC subsets were elevated as compared to healthy subjects. In addition, HPC and KDR+ cell fractions were higher than in MI, while CD133+ and KDR+CD133+ cell fractions were lower. There were differences in relative EPC fractions between the groups: KDR+ cells were the largest fraction in GBM while CD133+ cells were the largest fraction in MI. An increase in glioma malignancy grade coincided with an increase in the KDR+ fraction while the CD133+ cell fraction decreased relatively. Most plasma angiogenic factors were higher in GBM than MI patients. In both MI and GBM, the ratio of CD133+ HPCs correlated significantly with elevated levels of MMP9. In the GBM patients MMP9 correlated strongly with levels of all HPCs.

CONCLUSION

In conclusion, the data demonstrate that EPC traffic in patients with glioma is different from that in normal tissue regeneration. Therefore, the effects of glioma extent beyond the brain, and future therapies aimed at lowering KDR+ cells and HPCs may add to effective treatment.

The complement system in glioblastoma multiforme

The human complement system is represents the main effector arm of innate immunity and its ambivalent function in cancer has been subject of ongoing dispute. Glioma stem-like cells (GSC) residing in specific niches within glioblastomas (GBM) are capable of self-renewal and tumor proliferation. Recent data are indicative of the influence of the complement system on the maintenance of these cells. It appears that the role of the complement system in glial tumorigenesis, particularly its influence on GSC niches and GSC maintenance, is significant and warrants further exploration for therapeutic interventions.

Preoperative normalization of cortisol levels in Cushing's disease after medical treatment: consequences for somatostatin and dopamine receptor subtype expression and in vitro response to somatostatin analogs and dopamine agonists

CONTEXT

Corticotroph pituitary adenomas often highly express the dopamine 2 receptor (D₂R) and somatostatin receptor subtype 5 (sst₅). The sst₂ expression is relatively low, likely resulting from downregulating effects of high cortisol levels. This may explain why the sst₂-preferring somatostatin analog octreotide, compared with the multi-receptor-targeting somatostatin analog pasireotide, is generally ineffective in Cushing's disease.

OBJECTIVE

Our objective was to compare sst and D₂R expression levels between adenomas from patients with elevated and normalized preoperative urinary free cortisol excretion.

PATIENTS AND DESIGN

Corticotroph adenoma tissue was examined from patients from group 1 (n = 22; elevated preoperative urinary free cortisol) and group 2 (n = 11; mean duration of preoperative normocortisolism 10 weeks). Somatotroph adenoma tissue from 10 acromegalic patients was examined to compare receptor expression profiles.

MAIN OUTCOME MEASURES

We evaluated receptor mRNA and protein expression levels and effects of octreotide, pasireotide, and cabergoline on ACTH secretion by cultured human corticotroph adenoma cells.

RESULTS

The sst₂ mRNA expression in group 2 was 10-fold higher than in group 1 (P < .01), even comparable to that in somatotroph adenomas. There were no statistically significant differences in sst₅ and D₂R mRNA expression or in sst₂, sst₅, and D₂R protein expression between both groups of corticotroph adenomas. In responders, octreotide (n = 2 out of 4; -30.5% ± 10.4%) was less potent than pasireotide (n = 5 out of 6; -47.0% ± 4.2%) and cabergoline (n = 3 out of 4; -41.9% ± 3.1%) with respect to inhibition of ACTH secretion by adenomas from group 2.

CONCLUSIONS

After achieving normocortisolism induced by medical therapy, cortisol-mediated sst₂ downregulation on corticotroph adenomas appears to be a reversible process at the mRNA but not at the protein level. Octreotide remains less potent than pasireotide and cabergoline with respect to in vitro inhibition of ACTH secretion. Whether sustained normocortisolism induced by medical therapy induces re-expression of functional sst₂ protein in corticotroph adenomas and whether this increases the ACTH-lowering potency of octreotide remains to be established.

A Primary Extraosseous Ewing Sarcoma in the Cerebellopontine Angle of a Child: Review of Relevant Literature and Case Report

BACKGROUND AND IMPORTANCE:

We report the occurrence of a primary intracranial extraosseous Ewing sarcoma/peripheral primitive neuroectodermal tumor (EES/pPNET) in the cerebellopontine angle in a child.

CLINICAL PRESENTATION:

A 10-year-old girl presented with symptoms and signs of an infratentorial space-occupying lesion that was confirmed by magnetic resonance imaging and followed up by subtotal surgical resection. Tumor cells displayed membranous expression of CD99, and one of the typical translocations of EES/pPNET (chromosome 22) was demonstrated by cytogenetic analysis.

CONCLUSION:

The literature regarding the histopathological, molecular, radiological, prognostic, and therapeutic features of intracranial EES/pPNET is reviewed, emphasizing the distinction of this entity from the central PNET. Although exceptionally rare, intracranial EES/pPNET should be considered in the differential diagnosis of lesions in the cerebellopontine angle.

The CASPR2 cell adhesion molecule functions as a tumor suppressor gene in glioma

Genomic translocations have been implicated in cancer. In this study, we performed a screen for genetic translocations in gliomas based on exon-level expression profiles. We identified a translocation in the contactin-associated protein-like 2 (CASPR2) gene, encoding a cell adhesion molecule. CASPR2 mRNA was fused to an expressed sequence tag that likely is part of the nuclear receptor coactivator 1 gene. Despite high mRNA expression levels, no CASPR2 fusion protein was detected. In a set of 25 glioblastomas and 22 oligodendrogliomas, mutation analysis identified two additional samples with genetic alterations in the CASPR2 gene and all three identified genetic alterations are likely to reduce CASPR2 protein expression levels. Methylation of the CASPR2 gene was also observed in gliomas and glioma cell lines. CASPR2-overexpressing cells showed decreased proliferation rates, likely because of an increase in apoptosis. Moreover, high CASPR2 mRNA expression level is positively correlated with survival and is an independent prognostic factor. These results indicate that CASPR2 acts as a tumor suppressor gene in glioma.

IDH1 mutations in low-grade astrocytomas predict survival but not response to temozolomide

BACKGROUND

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) have been implicated in tumorigenesis of gliomas. Patients with high-grade astrocytomas with IDH1 or IDH2 mutations were reported to have a better survival, but it is unknown if this improved survival also holds for low-grade astrocytoma and whether these mutations predict outcome to specific treatment.

METHODS

We retrospectively investigated the correlation of IDH1 and IDH2 mutations with overall survival and response to temozolomide in a cohort of patients with dedifferentiated low-grade astrocytomas treated with temozolomide at the time of progression after radiotherapy.

RESULTS

IDH1 mutations were present in 86% of the 49 progressive astrocytomas. No mutations in IDH2 were found. Presence of IDH1 mutations were early events and significantly improved overall survival (median survival 48 vs 98 months), but did not affect outcome of temozolomide treatment.

CONCLUSION

These results indicate that IDH1 mutations identify a subgroup of gliomas with an improved survival, but are unrelated to the temozolomide response.

Filamin A mutation, a common cause for periventricular heterotopia, aneurysms and cardiac defects

Filamin A is an important gene involved in the development of the brain, heart, connective tissue and blood vessels. A case is presented illustrating the challenge in recognising patients with filamin A mutations. The patient, a 71-year-old woman, was known to have heart valve disease and bilateral periventricular nodular heterotopia when she died of a subarachnoid haemorrhage. Autopsy showed typical cerebral bilateral periventricular heterotopia and vascular abnormalities. Postmortally, the diagnosis of a filamin A mutation was confirmed. Recognition during life may prevent cardiovascular problems and provide possibilities for genetic counselling.

Safety and efficacy of frameless and frame-based intracranial biopsy techniques

BACKGROUND

Frameless stereotaxy or neuronavigation has evolved into a feasible technology to acquire intracranial biopsies with good accuracy and little mortality. However, few studies have evaluated the diagnostic yield, morbidity, and mortality of this technique as compared to the established standard of frame-based stereotactic brain biopsy. We report our experience of a large number of procedures performed with one or other technique.

PATIENTS AND METHODS

We retrospectively assessed 465 consecutive biopsies done over a ten-year time span; Data from 391 biopsies (227 frame-based and 164 frameless) were available for analysis. Patient demographics, peri-operative characteristics, and histological diagnosis were reviewed and then information was analysed to identify factors associated with the biopsy not yielding a diagnosis and of it being followed by death.

RESULTS

On average, nine tissue samples were taken with either stereotaxy technique. Overall, the biopsy led to a diagnosis on 89.4% of occasions. No differences were found between the two biopsy procedures. In a multiple regression analysis, it was found that left-sided lesions were less likely to result in a non-diagnostic tissue sample (p = 0.023), and cerebellar lesions showed a high risk of negative histology (p = 0.006). Postoperative complications were seen after 12.1% of biopsies, including 15 symptomatic haemorrhages (3.8%). There was not a difference between the rates of complication after either a frame-based or a frameless biopsy. Overall, peri-operative complications (p = 0.030) and deep-seated lesions (p = 0.060) increased the risk of biopsy-related death. Symptomatic haemorrhages resulting in death (1.5% of all biopsies) were more frequently seen after biopsy of a fronto-temporally located lesion (p = 0.007) and in patients with a histologically confirmed lymphoma (p = 0.039).

CONCLUSIONS

The diagnostic yield, complication rates, and biopsy-related mortality did not differ between a frameless biopsy technique and the established frame-based technique. The site of the lesion and the occurrence of a peri-operative complication were associated with the likelihood of failure to achieve a diagnosis and with death after biopsy. We believe that using intraoperative frozen section or cytologic smear histology is essential during a stereotactic biopsy in order to increase the diagnostic yield and to limit the number of biopsy specimens that need to be taken.

From expert opinion to evidence-based: changes in the gold standard of primary brain tumour diagnosis

Since 1997, significant progress has been made in the WHO guidelines for the diagnosis of primary tumours of the central nervous system. A large group of international experts was involved in editing the content; consensus on definitions and classifications was sought; and updated findings of genomic investigations were included. Nevertheless, significant inter-observer variability still exists in the histopathological diagnosis of several tumour types. The challenge for the near future is to identify histological and genotypic characteristics with prognostic or predictive value. With that aim, testing histological or molecular parameters in prospective clinical studies is indicated.

Randomized phase II trial of erlotinib (E) versus temozolomide (TMZ) or BCNU in recurrent glioblastoma multiforme (GBM): EORTC 26034

2005

Background: In 40–50% of GBM epidermal growth factor receptor (EGFR) is amplified, and often constitutively activated (EGFRvIII mutant). EGFR is therefore a potential therapeutic target. Previous studies suggested activity of EGFR tyrosine-kinase inhibitors in recurrent GBM, particularly in specific molecular subsets. This study explored erlotinib (E) activity in recurrent GBM. Methods: Randomized phase II trial. Eligibility criteria: histologically proven GBM, recurrent >3 months after radiotherapy, Karnofsky performance status (KPS) =70, no prior chemotherapy for recurrent disease, tissue sample for EGFR studies. Patients (pts) received E 150mg/day (300mg/day if on enzyme inducing anti-epileptic drugs [EIAEDs]), or control (TMZ 150–200mg/m2, day 1–5 q4wk or BCNU 60–80mg/m2 i.v., day 1–3 q8wk). If no significant toxicity, E was escalated to 200mg (500mg in patients on EIAEDs). The primary endpoint was 6 months’ PFS in =10/50 pts on E (20%); P0 was set at 15%, and P1 at 30%. Response was assessed with Macdonald’s criteria. EGFR amplification (FISH) and expression of EGFR, EGFRvIII and PTEN (immunohistochemistry [IHC]) were assessed. Results: 110 patients were randomized (54 E, 56 control: 27 TMZ; 29 BCNU). Median age 55 years; median KPS 90. All but 1 patient started treatment; median number of cycles was 2 for E, 4 for TMZ and 1 for BCNU. Grade 3/4 toxicities likely related to E: dermatological (5); hemorrhage (1). Grade 3/4 toxicities for control were mainly hematological (3 TMZ, 13 BCNU). Three pts discontinued E due to toxicity. Six-month PFS was 12% for E, 24% for control. Six and 12-month survival were 61% and 24% for E, and 63% and 26% for control. Two responses were seen on control; the best response on E was SD (n=6). Patients with EGFRvIII mutations (13 in E arm, 8 in control arm) had shorter PFS (p=0.007) and OS (p=0.004) regardless of treatment. Response to E was not correlated with EGFR expression, EGFR amplification or EGFRvIII mutation. Conclusions: This randomized, controlled phase II study did not find sufficient activity for erlotinib in the general population of recurrent GBM. The presence of EGFRvIII mutations was not predictive for response.

No significant financial relationships to disclose.

[Three patients with a paraneoplastic neurological syndrome: the significance of paraneoplastic antibodies]

Establishing the presence of paraneoplastic antibodies is important in identifying an often severe neurological syndrome as paraneoplastic and hence directing the search for an underlying neoplasm. A paraneoplastic neurological syndrome was diagnosed in 3 patients. The first was a 64-year-old woman in whom paraneoplastic encephalomyelitis was diagnosed. The diagnosis was strongly supported by a high titre of serum anti-Hu antibodies, despite three negative biopsies from a mediastinal mass. The patient died of a non-convulsive status epilepticus; autopsy revealed not only paraneoplastic encephalomyelitis but also small-cell lung cancer. The second patient was a 55-year-old woman with metastatic breast cancer. After a three-year period of progressive neurological deterioration, a high titre of anti-CV2/CRMP5 antibodies was detected, on the basis of which the clinical syndrome was diagnosed as paraneoplastic. She received immunotherapy and her condition stabilised. The third patient, a 41-year-old man, presented with severe limbic encephalitis. Biopsy from a paraaortic mass was positive for undifferentiated carcinoma. The patient had a high titre ofanti-Ma2 antibodies and was subsequently tested positive for serum alpha-foetoprotein (AFP) and beta-human-chorionic gonadotrophin (bta-HCG). During chemotherapy for a non seminoma testicular cancer, the limbic encephalitis improved both clinically and radiologically, but the patient died as a result of the toxicity of the treatment.

Raman spectroscopic characterization of porcine brain tissue using a single fiber-optic probe

Accurate targeting of diseased and healthy tissue has significantly been improved by MRI/CT-based navigation systems. Recently, intraoperative MRI navigation systems have proven to be powerful tools for the guidance of the neurosurgical operations. However, the widespread use of such systems is held back by the costs, the time consumption during operation, and the need for MR-compatible surgical devices. Raman spectroscopy is a nondestructive optical technique that enables real-time tissue identification and classification and has proved to be a powerful diagnostic tool in a large number of studies. In the present report, we have investigated the possibility of distinguishing different brain structures by using a single fiber-optic probe to collect Raman scattered light in the high-wavenumber region of the spectrum. For the Raman measurements, 7 pig brains were sliced in the coronal plain and Raman spectra were obtained of 11-19 anatomical structures. Adjacent brain structures could be distinguished based on their Raman spectra, reflecting the differences in their biochemical composition and illustrating the potential Raman spectroscopy holds as a guidance tool during neurosurgical procedures.

Molecular misreading: the occurrence of frameshift proteins in different diseases

Neuronal homoeostasis requires a constant balance between biosynthetic and catabolic processes. Eukaryotic cells primarily use two distinct mechanisms for degradation: the proteasome and autophagy of aggregates by the lysosomes. We focused on the UPS (ubiquitin-proteasome system). As a result of molecular misreading, misframed UBB (ubiquitin B) (UBB+1) is generated. UBB+1 accumulates in the neuritic plaques and neurofibrillary tangles in all patients with AD (Alzheimer's disease) and in the neuronal and glial hallmarks of other tauopathies and in polyglutamine diseases such as Huntington's disease. UBB+1 is not present in synucleinopathies such as Parkinson's disease. We showed that UBB+1 causes UPS dysfunction, aggregation and apoptotic cell death. UBB+1 is also present in non-neurological cells, hepatocytes of the diseased liver and in muscles during inclusion body myositis. Other frequently occurring (age-related) diseases such as Type 2 (non-insulin-dependent) diabetes mellitus are currently under investigation. These findings point to the importance of the UPS in diseases and open new avenues for target identification of the main players of the UPS. Treatment of these diseases with tools (e.g. viral RNA interference constructs) to intervene with specific targets is the next step.

Frameshift proteins in autosomal dominant forms of Alzheimer disease and other tauopathies

Frameshift (+1) proteins such as APP(+1) and UBB(+1) accumulate in sporadic cases of Alzheimer disease (AD) and in older subjects with Down syndrome (DS). We investigated whether these proteins also accumulate at an early stage of neuropathogenesis in young DS individuals without neuropathology and in early-onset familial forms of AD (FAD), as well as in other tauopathies, such as Pick disease (PiD) or progressive supranuclear palsy (PSP). APP(+1) is present in many neurons and beaded neurites in very young cases of DS, which suggests that it is axonally transported. In older DS patients (>37 years), a mixed pattern of APP(+1) immunoreactivity was observed in healthy looking neurons and neurites, dystrophic neurites, in association with neuritic plaques, as well as neurofibrillary tangles. UBB(+1) immunoreactivity was exclusively present in AD type of neuropathology. A similar pattern of APP(+1) and UBB(+1) immunoreactivity was also observed for FAD and much less explicit in nondemented controls after the age of 51 years. Furthermore, we observed accumulation of +1 proteins in other types of tauopathies, such as PiD, frontotemporal dementia, PSP and argyrophylic grain disease. These data suggest that accumulation of +1 proteins contributes to the early stages of dementia and plays a pathogenic role in a number of diseases that involve the accumulation of tau.

Primitive neuroectodermal tumours (PNETs) located in the spinal canal; the relevance of classification as central or peripheral PNET

Intraspinal location of central PNET (cPNET) is very rare. We present a case, critically review all publications of primary intraspinal cPNET occurrence and discuss tendencies in clinical presentation. In several previous attempts to summarise, authors often confused cPNET with peripheral PNET (pPNET). cPNET and pPNET are different entities with different immunohistochemical profiles and genetic backgrounds. Clinically, they are both aggressive tumours, but exhibit different characteristics in their local manifestation and metastatic spread. Survival rates are quite similar provided that treatment is applied according to the established protocols. Protocols in cPNET treatment differ from those for pPNET as regards the order of the treatment sub-modalities, specific chemotherapeutic regimen and intensity, radiation dose and its extent and consequently, the side effects. Therefore, failure to distinguish cPNET from pPNET leads to clinical guidance and treatment proposals based on false assumptions, which might effect outcomes. Often, distinguishing between cPNET and pPNET is easy, because they occur in different location. In the case of intraspinal tumour location, however, the differentiation is crucial because both primary cPNET and pPNET can occur intraspinally, even though this is rare. Nowadays, demonstrating the expression of MIC2 glycoprotein by immunocytochemical staining (CD99) showing the specific EWS-FLI1 chimeric gene presence in pPNET, offers an easy way of making a differential diagnosis between cPNET and pPNET.

[The oligodendroglioma: the value of histologic and genetic diagnosis in predicting sensitivity to chemotherapy]

During the past decade, there has been increasing interest in oligodendrogliomas because of their sensitivity to chemotherapy. However, making the histopathological diagnosis suffers from subjectivity in many cases. Oligodendrogliomas possess a 'genetic signature' that correlates well with the sensitivity of the tumour to chemotherapy, namely, the loss of parts of chromosome arms 1p and 19q. Hence, in cases of oligodendroglial tumors with disputable histology, additional genotyping to reveal losses on 1p/19q has become a valuable addition for making decisions for treatment.