bluuebunny/crossref_metadata_2025 huggingface dataset:
GCT-13. KRAS MUTATION IN PEDIATRIC INTRACRANIAL GERM CELL TUMORS
Authors: Khaiman Chusana , Techavichit Piti , Teerapakpinyo Chinachote , Shuangshoti Shanop
Published: June 2022

BACKGROUND: Intracranial germ cell tumors (IGCTs) are rare, highly curable neoplasms. KRAS is a gene in the KIT/RAS signaling pathway, and KRAS mutations were reported in patients diagnosed with IGCTs. OBJECTIVES: To describe clinicopathologic, molecular features of KRAS mutation and treatment outcome of children diagnosed with IGCTs. METHODS: A retrospective review in patients diagnosed with IGCTs at Department of Pediatrics, King Chulalongkorn Memorial Hospital from 2007 to 2019. DNA was extracted from formalin-fixed, paraffin-embedded (FFPE) tissue for the molecular study. Identifies mutations in codon 12,13 and 61 of the KRAS gene was performed by using the real-time PCR technique of the Cobas® test and pyrosequencing method. RESULTS: Eighteen patients were diagnosed with IGCTs (11 males and seven females). Age ranged from 5 to 14 years (median 10.5 years). The diagnosis was germinoma and non-germinomatous IGCTs in 9 patients each. Elevated markers were revealed in approximately 25% of patients. Four patients (2 patients with germinoma and 2 with non-germinomatous IGCTs) had leptomeningeal involvement. All patients underwent tumor biopsy and received neoadjuvant chemotherapy. Radiotherapy was given in 16 patients and craniospinal radiation (CSI) was given only in leptomeningeal metastasis. With the median follow-up of 26 months, overall survival is 88.9% in germinomas and 37% in non-germinomatous IGCTs. Mutation of the KRAS gene was detected by pyrosequencing technique in one patient. The mutation located at codon 61, frequency 38.3% units, nucleotide substitution CAA > CTA and amino acid substitution was Q61L. The patient who carries mutant gene was diagnosed germinomatous germinoma with CSF metastasis and eventually died from treatment-related toxicity. CONCLUSIONS: Our study revealed treatment outcomes of IGCTs in Thai children. We describe KRAS codon 61 mutation in metastasis germinoma patients with poor outcome, support KRAS codon 61 mutation (Q61L) may have a clinical correlation in IGCTs.
GCT-20. Multi-Institutional Analysis of Pediatric Relapsed/Refractory Central Nervous System Germ Cell Tumors
Authors: Nagabushan Sumanth , Dhall Girish , Abdelbaki Mohamed
Published: June 2022

Central nervous system (CNS) germ cell tumors (GCTs) constitute ~ 4% of primary pediatric brain tumors in the United States. While multimodality therapy approaches have ensured >80% survival benefit, these patients still experience relapses, with no established standard of care. Their rarity limits knowledge of their outcomes and associations with location, metastatic status, impact of surgery, serum, and cerebrospinal fluid (CSF) biomarkers, to only a few smaller trials and case series.This international multi-institutional retrospective study for relapsed/refractory germinomas and NGGCTs, will evaluate the association between different treatment modalities and 5-year OS and EFS; patterns of relapse, including along biopsy tracts; and potentially identify predictors of recurrence. De-identified patient data at primary and relapse time points will be collected focusing on treatment approaches such as surgery, conventional/high dose chemotherapy, photon/proton radiation therapy; timing and site of relapse; imaging characteristics and serum/CSF biomarkers (BHCG/AFP). Our collaborators include multiple sites across North America, Australia, Europe, Africa, South America, the Middle east, India, Singapore, and Malaysia. 6 recurrent intracranial germinomas on the CBTN (Children’s Brain Tumor Consortium) database were assessed, demonstrating a male gender preponderance (4) and recurring in the suprasellar region (3), frontal lobe (2) and spinal cord (1). 2 underwent gross total resection while 1 had biopsy only. Conventional or high-dose chemotherapy was administered in 5, while 2 received craniospinal and 1 proton radiation. 4 patients are alive. Median OS was 738 days and EFS 1093 days. However, biomarker (AFP/BHCG) data was unavailable. Updated results will be presented at the conference. With global partnership and contribution, we anticipate this study to help bridge existing gaps in our knowledge of this rare patient cohort and establish a consensus standard of care, through prospective clinical trials in the future. We acknowledge the CBTN for kindly providing data access.
GCT-22. OUTCOMES OF CHILDREN WITH LOCALIZED AND METASTATIC GERMINOMA TREATED WITH CHEMOTHERAPY FOLLOWED BY RADIATION THERAPY WITHOUT PRIMARY TUMOR BOOST
Authors: Bajin Inci Yaman , Foo Jen Chun , Bouffet Eric , Ertl-Wagner Birgit , Tsang Derek , Laperriere Norman , Dirks Peter , Drake James , Bartels Ute
Published: June 2022

BACKGROUND: Response-based radiation therapy has been the approach for germinoma after chemotherapy. However, the presence of residual lesions at the end of chemotherapy did not demonstrate a negative impact on progression-free survival (PFS). Similarly, resection of residual tumors after chemotherapy did not show a survival benefit. AIM: Our study objective was to determine long-term outcomes of a cohort who received chemotherapy and radiation therapy without primary tumor boost even in the absence of complete response to chemotherapy. METHOD: This retrospective study analyzed the outcome of germinoma patients diagnosed and treated at a tertiary care center from January 2006 to December 2021. RESULTS: Twenty-nine children (14 male; median age 12.8 years) were identified. Median follow-up was 63 months (range 9-187 months). Twenty children had localized disease and tumor location was suprasellar (n= 9), pineal (n= 10), and bifocal (n= 1) while 9 children had metastatic disease at presentation. All patients completed multi-agent chemotherapy followed by either whole ventricular (WVI) (23.4 Gy) (n = 23), whole brain (WBI) (23.4 Gy) (n = 5) or craniospinal radiation (CSI) (23.4 Gy) (n= 1). Two children, who had localized disease at presentation and received WVI after chemotherapy, relapsed 9 months and 32 months after completion of treatment respectively. None of them had local relapses. Location of relapse was distant, outside (n= 1) and inside (n= 1) the radiation field. Five-year PFS was 93% and overall survival (OS) was 100%. CONCLUSION: In this limited experience, excellent 5-year PFS and OS rates were achieved with chemotherapy followed by radiation therapy delivered without primary tumor boost. This study also demonstrated the absence of local relapse despite omitting primary tumor boost in patients with localized and metastatic germinoma.
HGG-03. PEDIATRIC BITHALAMIC GLIOMA H3K27M NEGATIVE AND EGFR POSITIVE: A DISTINCT ENTITY WITH POTENTIAL SENSIBILITY TO EGFR INHIBITORS
Authors: Hernandez Marta Cortes , Schiaffino Guiomar Gutierrez , Almeida Silvia Torrejon , MoroñO Sara Iglesias , Lara Bernardo Weil , Leon Maria Isabel Martinez , Alvarez Martina
Published: June 2022

INTRODUCTION: Brain tumors are the most common solid tumors of childhood and optimal therapeutic strategies for many subtypes remain unknown. Bithalamic gliomas, in contrast with unilateral, have frequent mutations in the EGFR oncogene and only rare Histone H3 mutation. These EGFR mutations are small inframe insertions within exon 20 or missense mutations within exon 7 and occur in absence of gene amplification. CASE REPORT: A previously healthy 10-years-old boy with adequate neuropsychomotor development was admitted with a 5-day-long headache. A brain magnetic resonance imaging (MRI) showed an expansive midline lesion with thalamic extension. The tumor showed no diffusion restriction or contrast enhancement. An endoscopic septostomy and biopsy were performed.The histopahotology showed a diffused astrocytoma grade II. The immunohistochemistry was negative for IDH1 and 2, BRAF mutation, P53 and H3K27M. Next generation sequencing (NGS) ruled out histone H3K27M mutation and showed EGFR mutation in exon 7. The patient experimented clinical and radiological disease progression in a few weeks, confirming the high grade glioma despite the histopahological diagnosis.He received radiotherapy (Total dose 54Gy) and after radiation he started target therapy with Osimertinib, a third generation tirosin kinase inhibitor. As a toxiticy, he experienced neutropenia Grade 2. Disease evaluation performed after 2 cycles showed stable disease. DISCUSSION: Our case report represents a distintc molecular class of pediatric-type bithalamic glioma characterized by EGFR alteration and absence of H3K27M mutation. EGFR inhibition may represent a potential therapeutic strategy in these highly aggressive gliomas.
HGG-13. Combined CDK inhibition and arginine-deprivation as targeted therapy for arginine-auxotrophic glioblastoma multiforme cells
Authors: Riess Christin , del Moral Katharina , Fiebig Adina , Kaps Philipp , Linke Charlotte , Hinz Burkhard , Rupprecht Anne , Frank Markus , Fiedler Tomas , Koczan Dirk , Troschke-Meurer Sascha , Lode Holger N , Engel Nadja , Classen Carl Friedrich , Maletzki Claudia
Published: June 2022

INTRODUCTION/BACKGROUND: Glioblastoma multiforme show constitutive activation of cyclin-dependent kinases (CDKs) or arginine auxotrophy. This renders tumor cells vulnerable towards arginine-depleting substances, such as arginine deiminase from Streptococcus pyogenes (SpyADI). Previously, we confirmed the susceptibility of patient-derived GBM cells towards administration of SpyADI as well as CDK inhibitors (CDKis). To improve effects, we applied a sequential (SEQ) CDKi/SpyADI approach to examine mechanistic insights and drug susceptibility. MATERIALS AND METHODS: Three arginine-auxotrophic patient-derived GBM lines with different molecular characteristics were cultured in 2D and 3D (spheres and glioma stem-like cells (GSC)) and effects of this combined CDKi/SpyADI approach were analyzed. This included viability staining via Calcein AM in 2D and 3D-Glo in 3D culture and cell death analysis via flow cytometry. Therapy-induced morphological changes were identified with transmission electron microscopy (TEM). Besides, 3D-invasiveness, cellular stress, and DNA damage responses were measured. RESULTS: All SEQ-CDKi/SpyADI combinations yielded synergistic antitumoral effects, characterized by impaired cell proliferation, invasiveness, and viability. Notably, this SEQ-CDKi/SpyADI approach was most effective in 3D models. Mitochondrial impairment was demonstrated by increasing mitochondrial membrane potential and decreasing oxygen consumption rate along with extracellular acidification rate after abemaciclib/SpyADI monotherapy or its combination regimens. TEM confirmed damaged mitochondria and endoplasmic reticulum together with increased vacuolization under CDKi mono- and SEQ- CDKi/SpyADI combination therapy. SEQ-abemaciclib/SpyADI treatment suppressed the DSB repair system via NHEJ and HR, whereas SEQ-dinaciclib/SpyADI treatment increased γ-H2AX accumulation and induced Rad51/Ku80. The latter combination also activated the stress sensor GADD45 and β-catenin antagonist AXIN2. CONCLUSION: This study highlights the antitumoral potential of a combined SpyADI/CDKi approach. We show that sequential application of these substances has complex effects on mitochondrial dysfunction, invasiveness, and DNA-damage response. This provides a good starting point for further proof-of-concept studies to move forward with this strategy.
HGG-22. Uptake of investigational therapy in children with High Grade Glioma
Authors: Toledano Helen , Abu-Quider Abed , Kaddan Walid , Fichman-Horn Suzanna , Kershenovich Amir , Michaeli Orli
Published: June 2022

High grade gliomas (HGG) in children carry a dismal prognosis. Standard therapy includes resection when possible, radiotherapy and sometimes the addition of temozolomide. There is no standard treatment for progression or relapse. Since November 2018 we have offered upfront molecular testing to all children with HGG who had biopsy/ resection. Testing was mainly done by next generation sequencing panel, and some had research based methylation profiling and RNA seq. We aimed to see whether families chose to receive additional investigational treatment as a result of the molecular testing results and whether the treatment involved participation in a clinical study, or whether treatment was compassionate. A total of 22 patients aged 2.8-16.8 years with HGG had a biopsy/resection over this three year period. Thirteen had diffuse midline glioma (DMG) of which 11 had the H3K27 mutation, and 9 were cortical. Six children had underlying predisposition syndromes: mismatch repair deficiency (n=3 proven + 1 highly suspected), neurofibromatosis1 (n=1), Li-Fraumeni (n=1). All the cortical gliomas had potential treatment options based on their molecular testing. 10/22 (45%) children received investigational therapy of which only three participated in a clinical study while the rest received compassionate therapy. Compassionate treatments included BRAF/MEK inhibitors (n=4), Larotrectinib (n=1), and immune checkpoint inhibitors (n=2). Of the 12 who did not receive investigational therapy, four, all cortical, have potential therapy options but are currently in remission. Of the remaining eight, two had very rapid clinical deterioration and died, and six (all DMG) did not wish/ were unable to travel abroad and no relevant clinical study was available locally. We conclude that the families of children with HGG are highly motivated to receive investigational therapy. Upfront molecular testing of these tumors, especially for cortical HGG, is imperative and there is a growing need for accessible clinical studies.
HGG-26. Comprehensive Genomic Profiling of Pediatric and AYA High-Grade Gliomas Reveals a High Prevalence of ATRX and Homologous Recombination Repair (HRR) Mutations
Authors: Kuang Zheng , Hiemenz Matthew , Huang Michael Angelo
Published: June 2022

BACKGROUND: Pediatric high-grade glioma (HGG) is a devastating heterogenous disease with a clear need for more effective treatment options. Advances in high-throughput molecular sequencing have advanced our understanding of these tumors and yet outcomes remain poor as only a very small subset of patients have demonstrated benefit from targeted therapy approaches. METHODS: We compiled genomic data from 980 pediatric (N=400) and AYA (18 to 30 yrs, N=580) HGG cases that underwent targeted, panel-based comprehensive genomic profiling (FoundationOne® CDx). RESULTS: Among pediatric patients, mutations in ATRX or HRR-related genes were among the most prevalent at 24.25% and 19.5%, respectively. Other commonly occurring mutations were seen in TP53 (58.25%), H3F3A (43%), and PIK3CA/PIK3R1 (22%). Among AYA patients, mutations in ATRX and HRR-related genes were seen in 51.72% and 17.24% of cases, respectively. The most common mutations seen in this older population were in TP53 (76.38%), IDH1/2 (50.86%), PI3KCA/PIK3R1 (20.52%), and H3F3A (18.28%). Among patients with diffuse midline glioma (harboring H3K27M mutations), ATRX and HRR mutations were reported in 21.27% and 13.57% of cases, respectively. Among pediatric patients with histone wild type HGG, mutations in ATRX and HRR-related genes occurred in 20.61% and 21.05% of cases, respectively. CONCLUSION: Alterations in ATRX and HRR-related genes are among the most prevalent mutations in pediatric and AYA HGG. Consideration should be made towards the development of subtype-specific treatment protocols using PARP and/or ATR inhibitors aimed at this subgroup of patients.
HGG-27. Understanding the role of PLAG family transcription factors in cortex development and tumorigenesis
Authors: Vaillant Jan , Hofmann Nina , Keck Michaela-Kristina , Jones David T W , Kutscher Lena M , Pfister Stefan M
Published: June 2022

Gliomas are the most common type of central nervous system (CNS) tumors in children. Therapy and outcome often reflect the grade of the tumor, with high grade glioma (HGG) leading to a significantly worse survival prognosis than low grade glioma. However, HGG are highly diverse regarding their molecular entities and clinical associations. In some pediatric-type histone 3 K27M mutated HGG, the zinc-finger transcription factor PLAG1 was previously found to be overexpressed, which is also confirmed by patient data from the INFORM program. Further, in a novel type of embryonic CNS tumors without histone mutations, the PLAG1-related genes PLAGL1/PLAGL2 are amplified. However, the consequences of aberrant PLAG gene expression on CNS tumor formation during development are unknown. Especially the understanding of downstream signaling pathways that are commonly altered by this transcription factor family could provide necessary starting points for more specific therapy. We use transgenic mouse models with targeted PLAG1 overexpression in neural stem and progenitor cells to investigate the function of PLAG1 in cerebral cortex development and tumorigenesis. We found that PLAG1 overexpression together with heterozygous loss of p53 activity causes neurological defects and impaired cortex development. Next, to understand how PLAG gene overexpression affects neural specification, we will overexpress the PLAG genes in embryonic neural stem and progenitor cells using in utero electroporation. After FACS isolation of electroporated cells and single nucleus RNA sequencing, we will assess how the overexpression changes the transcriptional trajectories of neural development in mouse cortex stem and progenitor cells. We hypothesize that an early event leads to the constitutive upregulation of PLAG genes, which are usually tightly regulated during development, in patients with pediatric brain tumors harboring aberrant PLAG gene expression. Deciphering the transcriptional downstream pathways of this aberrant expression in neural stem and progenitor cells seems promising to find new potential therapeutic targets.
HGG-28. CLIC1 and CLIC4 ion channel deficiency confers increased sensitivity to tumour treating fields and improved survival in paediatric glioblastoma
Authors: Griffin Michaela , Smith Stuart , Basu Surajit , Khan Raheela
Published: June 2022

Paediatric Glioblastoma Multiforme (pGBM) is a lethal brain cancer with an average survival of 14 months. Due to the scarcity of effective treatment, pGBM forms the leading cause of CNS cancer death in children. Optune™ is a non-invasive therapy that uses alternating electric fields – coined TT fields - to disrupt cancer cell division, however it is not currently approved in children. Evidence shows that ion channels not only regulate electrical signalling of excitable cells, but also play a crucial role in the development and progression of brain tumours, essential in cell cycle control and therefore presenting as valuable therapeutic targets. Candidate ion channel genes (ICG) associated with the malignant status of high-grade glioma (HGG) were identified via multivariate analysis of in-house and publicly available data sets. RNA sequencing of in-house patient tissues revealed an increased expression of CLIC1 and CLIC4, with pHGG exhibiting increased expression at protein and RNA levels in both the Paugh data set and in-house primary cell lines and TMAs. Clinical correlation determined that CLIC4 and CLIC1 deficiency was associated with increased overall survival (p=<0.03). siRNA depletion of CLIC1 and CLIC4 propagated a reduction in the proliferation, migration and invasion of pHGG cell lines and resulted in cell cycle arrest. Furthermore, CLIC1 and CLIC4 deficiency exacerbated the killing capacity of TT fields. Whole transcriptome gene expression analysis (Human Clairom™ Array) of paediatric GBM cell lines treated with tumour treating fields and found that cells treated with TTfields exhibited a down-regulation in CLIC1 and CLIC4 compared to untreated cells. These data provide rationale that genetic, electrical, and pharmacological manipulation of ion channels will reduce the capacity of childhood brain tumours to proliferate and invade. Therefore, may be a suitable target for combination therapy to enhance the treatment efficacy of TTfields and help bring this non-invasive therapy to paediatric patients.
HGG-31. Unique case of a bithalamic H3K27-wildtype diffuse midline glioma, EGFR-altered with methylated MGMT
Authors: Reinecke James , Cottrell Catherine , Rush Sarah , Judd Alexis , Palmer Joshua , Pierson Christopher , Lazow Margot , Wilson Yelena
Published: June 2022

BACKGROUND: Diffuse midline gliomas are aggressive pediatric brain tumors frequently associated with somatic mutations in histone genes H3F3A (H3.3) and HIST1H3B (H3.1), which promote gliomagenesis through reprograming of the epigenetic landscape by inhibiting the tri-methylation of H3K27 (H3K27-me3). H3K27M-mutant gliomas comprise over 80% of diffuse midline gliomas, and are characterized by dismal outcomes as well as near-ubiquitous absence of MGMT promoter methylation. The subset of H3K27-wildtype diffuse midline gliomas remains incompletely understood with regards to underlying pathogenesis, therapeutic targets, and prognosis. We present the clinical, imaging, histopathologic, and molecular characteristics of a pediatric patient with a bithalamic H3K27-wildtype diffuse midline glioma, EGFR-altered with methylated MGMT. CASE: A 10-year-old female presented with an infiltrative bithalamic T2-hyperintense mass lacking diffusion restriction or contrast enhancement on MRI. Initial pathological inspection from biopsy was consistent with high-grade neuroepithelial tumor favoring high-grade glioma, however, immunohistochemistry was negative for H3K27M and demonstrated reduced H3K27-me3. DNA sequencing uncovered mutations in EGFR (exon 20 insertion) and TP53 (R175H), with overexpression of EGFR and CDK6 (but not EZHIP) identified by RNA-sequencing. Methylation profiling was consistent with high-grade glioma, matching closest with glioblastoma, IDH-wildtype, with positive MGMT promoter methylation. Treatment was initiated with focal chemoradiotherapy with concurrent temozolomide, with plans for adjuvant temozolomide/ lomustine.DISCUSSION: Our case adds to growing evidence suggesting bithalamic tumors represent a distinct genetic and epigenetic subset of diffuse midline gliomas often defined by H3K27-wildtype status, loss of H3K27-me3, and EGFR receptor alterations. Our patient’s H3K27-wildtype, EGFR-altered tumor had reduced H3K27-me3 as well as positive MGMT promoter methylation, a molecular characteristic that has not been well-studied in H3K27-wildtype bithalamic gliomas, but is suspected to confer sensitivity to alkylating chemotherapy. The prevalence, prognostic impact, and therapeutic implications of MGMT promoter methylation in bithalamic H3K27-wildtype diffuse midline gliomas, including potential association with EGFR aberrations, requires further exploration.
HGG-34. Upfront Molecular Targeted Therapy for the Treatment of BRAF-mutant Pediatric High-Grade Glioma
Authors: Rosenberg Tom , Yeo Kee Kiat , Mauguen Audrey , Alexandrescu Sanda , Prabhu Sanjay P , Tsai Jessica W , Malinowski Seth , Joshirao Mrinal , Parikh Karishma , Sait Sameer Farouk , Rosenblum Marc K , Benhamida Jamal K , Michaiel George , Tran Hung N , Dahiya Sonika , Kachurak Kara , Friedman Gregory K , Krystal JulieI , Huang Michael A , Margol Ashley S , Wright Karen D , Aguilera Dolly , MacDonald Tobey J , Chi Susan N , Karajannis Matthias A
Published: June 2022

BACKGROUND: The prognosis for pediatric high-grade glioma (pHGG) is poor despite aggressive multi-modal therapy. Objective responses to targeted therapy with BRAF inhibitors have been reported in some patients with recurrent BRAF-mutant pHGG but are rarely sustained. METHODS: We performed a retrospective, multi-institutional review of patients with BRAF-mutant pHGG treated with off-label BRAF +/- MEK inhibitors as part of their initial therapy. RESULTS: Nineteen patients were identified, with a median age of 10.7 years (range: 1.8–20.3). Histologic diagnoses included HGG (n=6), glioblastoma (n=3), anaplastic ganglioglioma (n=4), diffuse midline glioma (n=3), high-grade neuroepithelial tumor (n=1), anaplastic astrocytoma (n=1), and anaplastic astroblastoma (n=1). Recurrent concomitant oncogenic alterations included CDKN2A/B loss, H3 K27M, as well as mutations in ATRX, EGFR and TERT. Eight patients received BRAF inhibitor monotherapy. Eleven patients received combination therapy with BRAF and MEK inhibitors. Most patients tolerated long-term treatment well with no grade 4–5 toxicities. Objective and durable imaging responses were seen in the majority of patients with measurable disease. At a median follow-up of 2.3 years (range,0.3–6.5), three-year progression-free (PFS) and overall survival (OS) for the cohort were 65% and 82%, respectively, and superior to a historical control cohort treated with conventional therapies. CONCLUSIONS: Upfront targeted therapy for patients with BRAF-mutant pHGG is feasible and effective, with superior clinical outcomes observed compared to historical data. This promising treatment paradigm is currently being evaluated prospectively in the Children’s Oncology Group ACNS1723 clinical trial.
HGG-37. A case ofETV6-NTRK3 fusion driven infantile hemispheric glioma (IHG) with acquired drug resistance against first- and second-generation NTRK-inhibitors
Authors: Ku Dennis T L , Liu Anthony P Y , Kan Amanda N C , Yuen Liz Y P , Shing M K , Yan Carol Y L , Fu Eric , Yau Jeffrey P W , Luk C W , Ng H K , Chan Godfrey C F
Published: June 2022

A 3-month-old girl had left cerebral infantile hemispheric glioma (IHG), H3 wild type (wt), Grade IV (WHO2020) with diffuse leptomeningeal and spinal metastasis. Craniotomies were performed twice which achieved partial resection. Histopathology revealed high grade glioma, Ki67 30-40%, mitosis and widespread necrosis. IHC showed H3wt, IDH-, and retained INI-1. RNAseq found ETV6-NTRK3 fusion. She was treated per Baby POG-9233, however after 3 cycles, there was mixed response (static for primary, partial response for metastasis). She had severe developmental delay, right hemiparesis and dysphagia. Aiming for better disease control and potential resectability, we switched to first-generation NTRK-inhibitor, Larotrectinib. MRI at 3 months showed significant interval reduction in tumour size, then became static at 6 months. She was stable with gradual neurological improvement until 10 months after Larotrectinib, there was worsening neurology and imaging confirmed tumour progression with haemorrhage. Craniotomy was performed for haemostasis and tumour debulking. Histopathology showed same IHG with ETV6-NTRK3 fusion. Targeted panel sequencing found NTRK3 p.Gly623Arg mutation, a solvent-front substitution responsible for acquired resistance to first-generation TRK-inhibitors. BRAFV600E and MET amplification were not detected. Larotrectinib was switched to second-generation NTRK-inhibitor, Selitrectinib. MRI at 1 month showed post-operative changes, but disease progressed at 3 months and in an accelerated manner over the course of 10 days while on therapy. Choice of conventional chemotherapy and radiotherapy were discussed, but the girl deteriorated rapidly and deceased (3 months from start of Selitrectinib, 19 months from diagnosis). CONCLUSION: IHG is aggressive with challenging surgery and medical treatment. The use of small molecular inhibitor requires careful consideration, i.e. treatment effect, toxicity and potential acquired drug resistance as showed in this case. For unresectable tumour, it may be inevitable as we also reported a similar case with ROS1 fusion. Access to newer novel agents is difficult while therapeutic effect is uncertain.
HGG-38. Gliomatosis cerebri/Glioblastoma with discordant histological and molecular profiles - treatment and outcome of a pediatric patient
Authors: Harrod Virginia , Morris Jason , Ho Winson
Published: June 2022

Gliomatosis cerebri is no longer recognized as a distinctive pathological diagnosis, but a manifestation of diffuse glioma involving at least three cerebral lobes. Lack of understanding in this manifestation of CNS neoplasms limits treatment for this aggressive disease. Here we present a case of stabilization of disease in a pediatric patient with unusual molecular profiles normally associated with aggressive tumor behavior. A nine-year-old male presented with acute onset of right-sided vision changes, headache and numbness of the left arm and leg for one day. He also had a three-month history of an asymptomatic bump on the right temporal skull bone. MRI of the brain was significant for diffuse thickening of the cortex of the entire right hemisphere (temporal>frontal>parietal lobes). No specific enhancing lesion or restricted diffusion was noted. Histologically, the tissue had findings of diffuse low-grade astrocytoma. Molecular genetic testing was notable for TERT and EGFR mutations which are more consistent with adult type high-grade astrocytic tumors. MGMT promoter methylation array was negative. Final diagnosis was glioblastoma, IDH and H3 wildtype. All the molecular features of this tumor were high-grade with an average progression free survival of less than 12 months. Despite the lack of methylation, we opted to include alkylating agents in a maintenance chemotherapy treatment plan following radiation therapy with concurrent temozolomide. Despite poor prognostic factors, the patient is alive without signs of progression 2.5 years post-diagnosis. Targeted agents were not used in upfront treatment for this patient. This is a rare case of stabilization of disease with conventional treatment in a very aggressive tumor. This case is a rare constellation of an ‘adult-type’ molecular profile in a pediatric patient with a low grade, less aggressive behavior profile, and highlights the need to better understand this rare subtype of tumors in children.
HGG-39. Integrative analyses of BRAFp.v600e mutated gliomas: from epigenetic to metabolic characteristics
Authors: Lhermitte Benoit , Wolf Thibault , Namer Izzie Jacques , Bund Caroline , Fuchs Quentin , Dontenwill Monique , Entz-Werlé Natacha
Published: June 2022

BRAF p.v600e mutation is encountered in brain tumors, mostly low grade pediatric diffuse gliomas (LGG) and epileptogenic glioneuronal tumors such as gangliogliomas (GG) or pleomorphic xanthoastrocytomas (PXA). Less frequently this mutation is present in high grade glial or glioneuronal tumors such as pleomorphic xanthoastrocytomas with anaplasia, anaplastic ganglioglioma, anaplastic diffuse astrocytomas or glioblastomas. Recently, few publications were highlighting differently the impact of BRAF mutation and CDKN2A deletion, as independent prognostic factors linked to a worst outcome in low grade forms. We studied retrospectively a monocentric cohort of 17 LGGs (14 GG and 3 pilocytic astrocytomas) and 7 BRAF pv600e HGG. The patients were aged below 20 years. We focused on extended tumors’ biology assessment (MethylEpic 850K, Next-Generation sequencing, RNA sequencing and metabolomics), as well as tumor immune microenvironment by immunohistochemistry. Among the LGGs, only one had a CDKN2A deletion and one a gain on chromosome 5. All except two LGGs had a complete surgical resection. Four of them were treated by chemotherapies but underwent relapses. All HGGs had a surgical resection followed by a first line chemotherapy (mainly Stupp protocol) and radiotherapy. Five patients relapsed rapidly, benefiting from targeted therapy with vemurafenib and/or biotherapy associating dabrafenib plus trametinib. Among those HGGs, we had both subgroups: “de novo” tumors and patients with a history of LGG tumors. Both were responding well to targeted treatments. The biology uncovers in all HGGs a loss of CDKN2A gene and/or protein. Additionally to this gene abnormality, specific transcriptomic expressions were associated to therapeutic response and immune microenvironment. Epigenetic modulation was linked to specific metabolic switches when BRAF p.v600e gliomas were getting higher grade features (e.g., glutaminolysis, serinolysis and phospholipidic metabolism). Those characteristics seem to be able to predict in LGG p.v600e potential evolution.
HGG-41. Glioma oncogenesis in the constitutional mismatch repair deficiency (CMMRD) syndrome
Authors: Guerrini-Rousseau Lea , Merlevede Jane , Denizeau Philippe , Andrejuolo Felipe , Varlet Pascale , Puget Stephanie , Beccaria Kevin , Blauwblomme Thomas , Cabaret Odile , Hamzaoui Nadim , Bourdeaut Franck , Faure-Conter Cecile , Muleris Martine , Colas Chrystelle , de Beaumais Tiphaine Adam , Castel David , Rouleau Etienne , Brugieres Laurence , Grill Jacques , Debily Marie-Anne
Published: June 2022

PURPOSE: Constitutional Mismatch Repair Deficiency (CMMRD) is a cancer predisposition due to bi-allelic mutations in one of the four main mismatch repair (MMR) genes (PMS2, MSH2, MSH6 or MLH1) associated with early onset of cancers, especially glioblastomas (GBM). Our aim was to decipher the molecular specificities of gliomas occurring in this context. METHODS: A comprehensive analysis of clinical, histopathological and genomic data (whole exome sequencing) was performed for 12 children with a CMMRD for which we had available frozen brain tumor material (10 GBM and 2 anaplastic astrocytomas). RESULTS: Eight patients harbored an ultra-mutated phenotype with more than 100 somatic non synonymous (NS) SNV/Mb. No correlation was observed between the number of mutation and sex, age, overall survival or mutated MMR gene. POLE and POLD1 exonuclease domain driver somatic mutations were described for eight and one patients respectively. The 4/12 tumors without POLE somatic mutation did not show the classical ultra-hypermutation pattern. All patients with POLE mutation had already more than 20 NS SNV/Mb (median 40, [range 23-114]) suggesting that the hypermutation phenomenon started before the appearance of the somatic POLE mutation. The mutational signatures of the tumors, dominated by the MMR signatures, were not modified after the onset of the POLE mutation when analyzing the different mutation bursts. Specific recurrent somatic mutations were observed in SETD2 (9/12), TP53 (9/12), NF1 (9/12), EPHB2 (8/12), and DICER1 (7/12). Only half of the tumors overexpressed PDL1 by immunohistochemistry and this overexpression was not associated with a higher tumor mutation burden. CONCLUSION: CMMRD-associated gliomas have a specific oncogenesis that does not trigger usual pathways and mutations seen in sporadic pediatric or adult GBM. Frequent alterations in other pathways (e.g. MAPK or DNA-PK pathway) may suggests the use of other targeted therapies aside from PD1 inhibitors.
HGG-47. Comparative analysis of the Histone H3 mutant protein interactome landscape in paediatric high-grade gliomas
Authors: Porter William , Sulman Joshua , Foot Katie , Rahman Ruman , Grundy Richard , Layfield Robert , Haque Farhana
Published: June 2022

There have been no significant improvements in the treatments for childhood and adolescent High-Grade Glioma (pHGG) and Diffuse Intrinsic Pontine Glioblastoma (DIPG), which have a very poor prognosis. These cancers harbour mutations affecting histone 3 (H3) proteins, 80% of DIPGs harbour histone H3.1 and H3.3 K27M somatic mutations whilst 30% of pHGGs exhibit H3.3 G34R or G34V mutations. Several studies have highlighted the epigenetic changes associated with these mutations, however their precise role in tumourigenesis is still unknown. We hypothesize that H3 mutations promote an aberrant interaction landscape and analysis of these interactome will highlight important pathophysiological consequences in these tumours. Two different affinity chromatographic proteomic analyses were performed using different recombinant H3 wild type (WT) and H3 mutant histone proteins (K27M, G34R and G34V) to purify their binding partners, from cell extracts of control and pHGG/DIPG patients cell lines. The purified samples were then subjected to Liquid Chromatography-Mass Spectrometry (LC-MS) to identify their co-bound partners. The results have isolated unique and common differential interaction partners of the H3 mutants and with cellular proteins in comparison to H3 WT protein, in the pHGG tumour cells. The role these altered protein interactions are being investigating in tumour initiation, progression and/or maintenance of H3 mutated pHGG/DIPG, with the aim to manipulate their function as alternate therapeutic intervention. Results of these analyses/experiments will be presented.
HGG-55. An adolescent with a High-Grade Glioma: persuing a specific diagnosis
Authors: Luz Inês Romão , Rebelo Olinda , Costa José Augusto , Carvalho Alice
Published: June 2022

BACKGROUND: Recognizing the value of molecular parameters provides evidence with repercussions on diseases classification. CLINICAL CASE: A thirteen-year-old girl was admitted in coma at the Intensive Care Unit due to a hemorrhagic stroke. CT revealed an expansive left frontal lobe lesion with perilesional edema and compression signs by an extensive hematoma. She underwent an emergency decompressive craniotomy for hematoma drainage, and the lesion was biopsied. The subsequent MRI showed a large heterogeneous mass with a cystic component. A first subtotal resection of the lesion was performed considering the language area. The histopathological examination showed tumor cells organized in perivascular pseudorosettes around the central hyalinized thickened blood vessel throughout the tumor, a pattern typically encountered in astroblastoma. Immunochemistry stains revealed a positive reactivity for GFAP, Olig2, and synaptophysin. The molecular study found a BRAFV600E mutation and homozygous CDKN2A e CDKN2B deletions; no TERT amplification, BCORL1, nor MN1 gene rearrangements were identified. She completed six weeks of radiotherapy without neurological signs/symptoms. A new surgical intervention was done 12 weeks later due to a slight increase of residual lesion. The rapid growth and the presence of viable tumor cells justified the therapy with irinotecan and bevacizumab, with mild adverse effects. One year after diagnosis, the adolescent is clinically well, without neurologic deficits and the MRI without evidence of residue or tumor recurrence. DISCUSSION: We began therapy based on morphological diagnosis. Complete resection and radiotherapy proved to be beneficial as in other high-grade gliomas, but the value of other therapies is still unknown. The BRAF gene variant would allow treatment with dabrafenib (in association with trametinib) or vemurafenib; however, she presents molecular findings associated with poor prognosis (CDKN2A deletion) that may impair the effectiveness of these therapies. According to the new WHO classification, the absence of MN1 alterations precludes the diagnosis of astroblastoma.
HGG-56. Spatial mapping of the tumor micro-environment in pediatric glioma
Authors: Messiaen Julie , Antoranz Asier , Van Herck Yannick , Verhaaren Ben , Nazari Pouya , Sebastian Ivey , Milli Giorgia , Bosisio Francesca , Pey Jon , Bempt Isabelle Vanden , Sciot Raf , Jacobs Sandra , De Smet Frederik
Published: June 2022

High-grade glioma are the main cause of cancer-related death in children. The highly heterogeneous composition of the tumor cells and their interactions with the tumor micro-environment (TME), contribute substantially to the poor response to treatment and the high levels of morbidity and mortality. Here, we used high-dimensional, multiplexed immunohistochemistry to map the single-cell tissue architecture of 26 pediatric glioma samples covering 8 histologic diagnoses, allowing us to determine the spatial distribution of the various tumoral subtypes and how these interact with their local immune-microenvironment. Overall, this analysis showed that tumor grade anti-correlated with the amount of infiltrating cytotoxic T-lymphocytes (CTLs), which were typically more exhausted in the higher grade tumors. In addition, tumor associated macrophages were primarily infiltrating from the blood and presented an M2-like anti-inflammatory phenotype which became more extended with tumor grade. Using the spatial information, possible cell-cell interactions could be determined. In lower grade glioma, we observed an increased activation level of CTLs that were closely located to neighboring T-helper cells. In pediatric glioblastoma, on the other hand, CTLs, even though they were located close to a T-helper cell, could only minimally be activated, and showed more extended exhaustion when residing further away. Additionally, the activation of the CTLs was associated to the distance to the closest PD-L1 positive macrophage in pilocytic astrocytoma and desmoplastic infantile ganglioglioma. In conclusion, with the use of multiplex immunohistochemistry, we are able to study the tumor and TME of pediatric glioma in depth on a single-cell and spatial level, which allows us to further study the heterogeneous landscape of these tumors.
IMG-02. Improved prediction of postoperative paediatric cerebellar mutism syndrome using an artificial neural network
Authors: Sidpra Jai , Marcus Adam P , Löbel Ulrike , Toescu Sebastian , Yecies Derek , Grant Gerald , Yeom Kristen , Mirsky David M , Marcus Hani J , Aquilina Kristian , Mankad Kshitij
Published: June 2022

BACKGROUND: Postoperative paediatric cerebellar mutism syndrome (pCMS) is a common but severe complication which may arise following the resection of posterior fossa tumours in children. Two previous studies have aimed to preoperatively predict pCMS, with varying results. In this work, we examine the generalisation of these models and determine if pCMS can be predicted more accurately using an artificial neural network (ANN). METHODS: An overview of reviews was performed to identify risk factors for pCMS, and a retrospective dataset collected as per these defined risk factors from children undergoing resection of primary posterior fossa tumours. The ANN was trained on this dataset and its performance evaluated in comparison to logistic regression and other predictive indices via analysis of receiver operator characteristic curves. Area under the curve (AUC) and accuracy were calculated and compared using a Wilcoxon signed rank test, with p<0.05 considered statistically significant. RESULTS: 204 children were included, of whom 80 developed pCMS. The performance of the ANN (AUC 0.949; accuracy 90.9%) exceeded that of logistic regression (p<0.05) and both external models (p<0.001). CONCLUSION: Using an ANN, we show improved prediction of pCMS in comparison to previous models and conventional methods.
IMG-03. Impact of childhood cerebellar tumor surgery on cognition: Can fMRI serve as a surrogate marker?
Authors: Dorfer Christian , Pletschko Thomas , Seiger Rene , Chocholous Monika , Kasprian Gregor , Roessler Karl , Kollndorfer Kathrin , Schöpf Veronika , Leiss Ulrike , Slavc Irene , Prayer Daniela , Lanzenberger Rupert , Czech Thomas
Published: June 2022

BACKGROUND: Childhood cerebellar pilocytic astrocytomas harbour excellent overall survival rates after surgical resection, but the patients may exhibit specific cognitive and behavioural problems emphasising our current understanding of the cerebellar role in cognition. Functional MRI has catalysed the mechanistic insights into brain functional systems and has already been linked with the neuropsychological performance. We aimed to exploit the question whether functional MRI can be used as a surrogate measure for the cognitive outcome assessment of these patients. METHODS: We investigated 13 patients (median age 22.0 years, range 15.2 – 31.7) after a median interval between surgery and examination of 15.0 years (range 4.2 – 20.8) and 16 matched controls. All subjects underwent a functional 3T MRI scans in a resting state condition and a battery neuropsychological tests. RESULTS: Patients showed a significantly increased functional connectivity in the precuneus compared to controls (p<0.05) and at the same time impairments in various domains of neuropsychological functioning such as a lower mean WIE IQ percentile (M = 48.62, SD = 29.14), lower scores in the TMT letter sequencing (M = 49.54, SD = 30.66), worse performance on the WIE subtest Digit Symbol Coding (M = 38.92, SD = 35.29), subtest Symbol Search (M = 40.75, SD = 35,28), and TAP divided attention task (M = 783.92, SD = 73.20). CONCLUSION: Functional MRI has the potential to serve as a surrogate measure for the cognitive outcome assessment. The precuneus brain region is heavily involved in the cerebral associative oversight of cerebellar cognitive function.
IMG-12. Transient atypical brain and spine MRI features after high-dose chemotherapy may represent clumps of CD34+ hematopoietic stem cells
Authors: Ramaglia Antonia , Arkhangelskaya Elena , Sementa Angela Rita , Morana Giovanni , Rossi Andrea , Faraci Maura , Piccolo Gianluca , Crocco Marco , Milanaccio Claudia , Garrè Maria Luisa , Verrico Antonio
Published: June 2022

High-dose chemotherapy is a therapeutic option in selected cases of pediatric high-grade brain tumor (pHGBT). Following high-dose chemotherapy, bone marrow is reconstituted by means of CD34+ peripheral blood stem cell (PBSC) infusion. Intravenously injected PBSCs have been reported to migrate to the Central Nervous System (CNS) and to persist for weeks. We report two cases of pHGBT in which, following PBSC infusion, we observed peculiar brain MRI signal alterations suggestive of clumps of CD34+ cells. A 15-month-old female underwent surgery and chemotherapy for an infratentorial, non-disseminated, Atypical Teratoid Rhabdoid Tumor. Following the second course of high-dose chemotherapy, MRI excluded residual disease, but revealed two contrast-enhancing nodules in the supratentorial ventricular system, with no evidence of diffusion restriction, unlike the primary tumor. Cerebrospinal fluid was collected by means of lumbar puncture and centrifuged: no neoplastic cells were found, while a few cells were positive when immunostained with anti-CD34 antibody. As no disease progression was documented, the patient completed her treatment with focal radiotherapy. Three months after the end of therapy, MRI showed new enhancing nodules with restricted diffusion, in keeping with leptomeningeal spread of disease; these progressively increased in size, despite subsequent lines of treatment, while the above-mentioned ventricular nodules shrank. Similar transient alterations were detected in a 4-year-old boy who had received treatment for high-risk Medulloblastoma, including high-dose chemotherapy. CONCLUSIONS: In the setting of new enhancing brain and spine findings with atypical MRI features, after high-dose chemotherapy to treat pHGBT, the hypothesis of CNS homing of CD34+ hematopoietic stem cells should be considered in the differential diagnosis.