bluuebunny/crossref_metadata_2025 huggingface dataset:
IMMU-03. Synergy between TMZ and individualized multimodal immunotherapy to improve Overall Survival of IDH1 wild-type MGMT promoter-unmethylated GBM patients
Authors: Van Gool Stefaan , Makalowski Jennifer , Bitar Michael , Van de Vliet Peter , Schirrmacher Volker , Stuecker Wilfried
Published: June 2022

The prognosis of IDH1 wild-type MGMT promoter-unmethylated GBM patients remains poor. Addition of Temozolomide (TMZ) to first-line local treatment shifted the median overall survival (OS) from 11.8 to 12.6 months. We retrospectively analysed the value of individualized multimodal immunotherapy (IMI) to improve OS in these patients. All adults meeting the criteria and treated 06/2015-06/2021 were selected. Thirty-two patients (12f, 20m) had a median age of 47y (range 18-69) and a KPI of 70 (50-100). Extent of resection was complete (11), <complete (12) or not documented (9). Seven patients were treated with surgery/radio(chemo)therapy and subsequent IMI (Group-1); 25 patients were treated with radiochemotherapy followed by maintenance TMZ plus IMI during and after TMZ (Group-2). Age, KPI and extent of resection were not different amongst both groups. The median OS of group-1 patients was 11m (2y OS: 0%). Surprisingly the median OS of group-2 patients was 22m with 2y OS of 36% (CI95%: 16-57), which was significantly (Log-rank: p = 0.0001) different from group-1. The data suggest that addition of IMI after local therapy on its own has no relevant effect on OS in these GBM patients, similar to maintenance TMZ. However, the combination of both TMZ + IMI significantly improved OS. This finding might also have implications in the search for novel combined treatment approaches for children with malignant glioma.
IMMU-09. Interim analysis from BrainChild-03: Seattle Children’s Locoregional B7-H3 CAR T Cell Trial for Children with Recurrent Central Nervous System Tumors and DIPG
Authors: Vitanza Nicholas , Gust Juliane , Wilson Ashley , Huang Wenjun , Chen Dickson , Meechan Michael , Biery Matt , Myers Carrie , Tahiri Sophie , Crotty Erin , Leary Sarah , Cole Bonnie , Browd Samuel , Hauptman Jason , Lee Amy , Albert Catherine , Pinto Navin , Orentas Rimas , Gardner Rebecca , Jensen Michael , Park Julie
Published: June 2022

BrainChild-03 is a phase 1 clinical trial delivering repeated locoregional 2nd generation B7-H3 CAR T cells with 4-1BB co-stimulation to children with central nervous system (CNS) tumors without lymphodepleting chemotherapy. The primary endpoints are feasibility and safety, with secondary endpoints of disease response and correlatives of CAR T cell activity. There are 3 arms: (A) – weekly delivery into the tumor cavity, (B) – weekly delivery into the lateral ventricle for metastatic disease, (C) – biweekly delivery into the lateral ventricle for diffuse intrinsic pontine glioma (DIPG). In total, 23/24 (96%) enrolled patients have had successful CAR T manufacturing. 16/24 patients are evaluable and have received a total of 141 intracranial CAR T cell doses. Unevaluable patients include 5 never treated and 3 who progressed prior to receiving the minimum doses to become evaluable. The most common adverse events have been headache (16/16, 100%), nausea/vomiting (12/16, 75%), and fever (10/16, 63%). There has been 1 DLT for an intratumoral hemorrhage and no cytokine release syndrome (CRS). 7 evaluable patients with DIPG (Arm C) have received a cumulative 50 infusions. 5/7 DIPG patients enrolled after progression and have a median survival of 246.5 days post-initial CAR T cell infusion, with 4/5 still alive. The 2 DIPG patients enrolled prior to progression had radiographic improvement, including 1 with improvement of a cranial nerve 6 palsy who self-withdrew from protocol therapy after 18 infusions over 12 months and 1 still on protocol therapy after 11 infusions over 6 months. DIPG patients have had increased CSF levels of proinflammatory mediators (e.g. CXCL10, CCL2, IFNg, GM-CSF, IL-12) without systemic cytokine changes. 5/7 DIPG patients had detectable CAR T cells in their CSF post-infusion. Ultimately, the preliminary experience suggests locoregional delivery of B7-H3 CAR T cells may be feasible and tolerable in children with CNS tumors, including DIPG.
LGG-14. LOGGIC (Low Grade Glioma in Children) Core BioClinical Data Bank: Establishment and added clinical value of an international molecular diagnostic registry for pediatric low-grade glioma patients
Authors: Hardin Emily C , Schmid Simone , Sommerkamp Alexander , le Simon Michè , Caspar Claudia , Bodden Carina , Heipertz Anna-Elisa , Sievers Philipp , Wittmann Andrea , Perera Ashwyn A , Milde Till , Pfister Stefan M , von Deimling Andreas , Driever Pablo Hernáiz , Koch Arend , Hargrave Darren , Witt Olaf , Capper David , Sahm Felix , Jones David T W , van Tilburg Cornelis M
Published: June 2022

BACKGROUND: The international, multicenter registry LOGGIC Core BioClinical Data Bank aims to enhance the understanding of tumor biology in pediatric low-grade glioma (pLGG) and provide clinical and molecular data. In addition to routine histopathological and molecular analyses, LOGGIC Core determines the driver alteration as precisely as possible to support treatment decisions and participation in interventional trials. Hence, the question arises whether comprehensive implementation of RNA sequencing using Fresh Frozen (FF) tumor tissue to identify underlying gene fusions improves diagnostic accuracy and provides a clinical benefit.

METHODS: Establishment of an international molecular and clinical registry including the logistical and analytical pipeline. First analysis of all patients age 0 to 18, which were included in Germany as part of the German HIT-LOGGIC-program between April 2019 and February 2021, and for whom FF tissue was available. This included histopathological evaluation, immunohistochemistry, 850k methylation analysis, gene panel sequencing, RNA sequencing using FF tissue.

RESULTS: FF tissue was available in 178/379 included cases. RNA sequencing was performed on 125 samples. In this prospective, population based cohort, we confirmed KIAA1549:BRAF-fusion (57%), BRAFV600E-mutation (9%) and FGFR1-changes (10%) as most frequent alterations. 12% of cases presented rare gene fusions (e.g. TPM3:NTRK1, EWSR1:VGLL1, GOPC:ROS1, SH3PXD2A:HTRA1, PDGFB:LRP1). In 19% of cases, RNA sequencing detected an actionable target not identified by conventional methods.

CONCLUSION: The addition of RNA sequencing reveals clinically relevant alterations including rare gene fusions. By demonstrating improvement of diagnostic accuracy and making precision oncology studies (MEKi/RAFi/ERKi/NTRKi/FGFRi/ROSi) more accessible, the added value for pLGG patients becomes apparent. LOGGIC Core is currently being rolled out internationally and aims to define the new state of the art standard molecular diagnostics. We propose to include RNA sequencing as part of routine diagnostic procedures for all pLGG patients, especially in tumors where no common MAPK alteration was identified.
LGG-25. The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics
Authors: Sigaud Romain , Rösch Lisa , Gatzweiler Charlotte , Benzel Julia , von Soosten Laura , Peterziel Heike , Najafi Sara , Ayhan Simay , Gerloff Xena F , Hofmann Nina , Büdenbender Isabel , Foerster Kathrin I , Burhenne Jürgen , Longuespée Rémi , van Tilburg Cornelis M , Jones David T W , Pfister Stefan M , Knoerzer Deborah , Kreider Brent , Sauter Max , Pajtler Kristian W , Zuckermann Marc , Oehme Ina , Witt Olaf , Milde Till
Published: June 2022

Ulixertinib (BVD-523) is a catalytic ERK1/2 inhibitor that showed promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Pediatric low-grade gliomas (pLGG) are the most common pediatric brain tumors, with the most frequent driving alterations in the MAPK pathway. The anti-tumor activity of ulixertinib in pLGG and its potential synergism in combination with MEK inhibitors, senolytics, and chemotherapy were investigated in vitro using metabolic activity, MAPK reporter assay and high-content microscopy in pLGG-derived cell lines (DKFZ-BT66 - KIAA:BRAF fusion; BT40 - BRAF V600E mutation and CDKN2A/B deletion). The most clinically relevant combinations were further validated in vivo: 1) in zebrafish embryo models (BT40 and DKFZ-BT66 yolk sac injection) and 2) in NSG mice (BT40 orthotopic PDX) including in vivo pharmacokinetic and -dynamic analyses. Ulixertinib inhibited MAPK pathway activity in all models and reduced cell viability in the BRAF V600E mutated cell line at concentrations in the nanomolar range. In vivo pharmacokinetic and -dynamic analyses showed penetrance of the drug into mouse brain tissue and on-target activity, with concentrations above the in vitro IC50 and reduction of MAPK activity. Ulixertinib treatment slowed tumor growth and significantly increased survival in NSG mice with BT40 xenografts. Ulixertinib showed indications for anti-proliferative synergy in vitro in combination with MEK inhibitors (trametinib, binimetinib) or BH3 mimetics (navitoclax, A-1331852). Combinations with chemotherapy (carboplatin, vinblastine) were at most additive. Indications for synergy with binimetinib and navitoclax were confirmed in the zebrafish embryo models. In the NSG mouse model, the combination of ulixertinib with senolytics induced effects on tumor growth and survival comparable to ulixertinib monotherapy. Ulixertinib shows promising potential as a clinically relevant therapeutic option for the treatment of pLGG to be further investigated in upcoming clinical trials. Potential synergism with MEK inhibitors and BH3 mimetics was noted and warrants further investigation.
LGG-42. Thromboembolic toxicity observed with concurrent trametinib and lenalidomide therapy
Authors: Chan Priya , Sabus Ashley , Hemenway Molly , Chatfield Kathryn , Foreman Nicholas , Dahl Nathan
Published: June 2022

INTRODUCTION: Event-free survival of pediatric low-grade glioma (pLGG) is poor, and patients often require multiple treatment strategies. The hallmark of pLGGs are genetic aberrations of the mitogen-activated protein kinase pathway, which lead to constitutive pathway activation. MEK and RAF inhibitors target this pathway and are efficacious in early phase trials in recurrent pLGGs. However, not all patients respond to monotherapy, and many experience progression after completion of therapy. Evaluating combination therapies that may enhance efficacy or prolong disease stabilization is warranted. Lenalidomide is an immunomodulatory agent with an anti-tumor effect demonstrated in phase 1 trials in recurrent pediatric central nervous system (CNS) tumors. OBJECTIVE: To describe our institutional experience using concurrent trametinib and lenalidomide in the treatment of primary pediatric central and peripheral nervous system (PNS) tumors. METHODS: Retrospective review of patients’ medical records. RESULTS: Four patients with locally recurrent primary CNS or PNS tumors, three with WHO grade II pilomyxoid astrocytomas and one with a plexiform neurofibroma, were treated with trametinib and lenalidomide concurrently. Two patients developed severe thromboembolic events. One patient was treated with combination therapy for seven months until trametinib and lenalidomide were held after urgent ventriculoperitoneal shunt revision. Shortly following shunt revision, he experienced near-complete vision loss. MRI of the brain demonstrated a left posterior watershed territory hypoxic-ischemic injury. In a second patient, after four months of combination therapy, surveillance echocardiogram showed an incidental finding of severe biventricular dysfunction with a left ventricular ejection fraction (LVEF) of 17.7% and two mural thrombi in the left ventricular apex. She started losartan and enoxaparin and discontinued trametinib and lenalidomide. Her LVEF normalized four months later, and the mural thrombi resolved. CONCLUSIONS: Given the severe thromboembolic events experienced by these patients treated with concomitant trametinib and lenalidomide, this combination requires further investigation, and we urge caution if used concurrently.
LGG-51. Resection extent and BRAF V600E mutation status determine postoperative growth velocity in pediatric Low-grade glioma: Results from a single-center cohort analysis
Authors: Gorodezki David , Sosa Jordana , Holzer Ursula , Queudeville Manon , Zipfel Julian , Bevot Andrea , Schittenhelm Jens , Nägele Thomas , Ebinger Martin , Schuhmann Martin
Published: June 2022

Despite the favourable outcome and excellent long-term overall survival rates, pediatric LGG show vast variety of clinical behavior and limited predictability regarding progress or senescence. We comparatively analyzed the tumor growth velocity (TGV) of PLGG post subtotal resection (STR) to investigate the impact of surgery, histological subtype, tumor location and the most frequent BRAF aberrations (BRAF V600E mutation vs KIAA1549-BRAF fusion) on tumor growth rates, aiming to identify potential variables to prognosticate further progress or senescence. A total of 53 patients vs 94 patients in the pre- and postoperative cohort, respectively, could be observed over a mean follow-up time of 40.2 vs 60.1 months. Distribution of histopathological diagnosis and tumor sites showed similarity to previously published cohort studies. Comparative analysis of pre- and postoperative TGV showed a significant difference as mean preoperative TGV accounted for 0.264 cm³/mo, while postoperative TGV after 1st, 2nd and 3rd STR showed reduction to 0.085 cm³/mo, 0.024 cm³/mo and -0.016 cm³/mo, respectively (p < 0.001). Results remained significant after excluding patients who had obtained (neo)adjuvant treatment. Resection extent showed remarkable correlation with postoperative reduction of TGV (R = 0.97, P < 0.001). Comparison of postoperative TGV of BRAF V600E mutant LGG and BRAF wild-type LGG showed significant difference of means (0.123 cm³/mo and 0.016 cm³/mo, p = 0.47), consistent to previous analyses, suggesting BRAF V600E positive LGG as a high-risk subgroup. Histological type, tumor location and BRAF-KIAA1549 fusion showed no significant impact on postoperative TGV. The results suggest that surgery, beyond cytoreductive purpose, impacts PLGG kinetics post STR by inducing a significant deceleration of tumor growth. As postoperative growth velocity showed clear correlation to resection extent and residual tumor burden, surgery, as radical as possible while preserving neurological function, appears to remain the mainstay of therapy besides advancing therapeutic approaches.
LGG-53. Evaluation of KIAA-BRAF1549 fusions in pilocytic astrocytoma with clinicopathological correlation
Authors: Dandapath Iman , Mahajan Dr Swati , Sahu Dr Saumya , Sharma Dr Mehar Chand , Suri Dr Ashish , Suri Dr Vaishali
Published: June 2022

Background

Pilocytic astrocytomas (PAs) are the primary tumors most frequently found in children and adolescents, accounting for 5.4% of all gliomas. The overall prognosis of PAs is good, yet a substantial no of cases have a poor outcome, with recurrence, and ultimately death. The KIAA1549-BRAF fusion is a useful putative diagnostic marker for PAs and BRAF also is an important therapeutic marker.

Aim and Objectives

To study the frequency of KIAA1549-BRAF fusion (16-9, 15-9 and 16-11) in different locations of PAs using qRT-PCR technique in FFPE samples.

Methodology

Three different exon rearrangements of KIAA1549-BRAF (16-9, 15-9 and 16-11) fusions were assessed in 50 cases of PAs by using qRT-PCR (gold standard). FISH assay was also performed in all the cases.

Results

Out of 50 PAs, 32 were localised in midline structures such as the cerebellum, optic pathway, hypothalamus, and brain stem while 18 in non-midline regions like the cerebral hemispheres. Majority of the cases (35/50); 70% were positive for KIAA1549-BRAF fusion by RT-PCR. Of these, (16/35); 45.7% harboured 15-9 fusion, (15/35); 42.8% harboured 16-9 fusion, and only (4/35); 11.4% had 16-11 fusion. Only (24/30); 48% KIAA1549-BRAF showed fusion by FISH assay. There was 54.2% concordance between FISH and RT-PCR results. KIAA1549-BRAF fusion was observed in 78% of midline and 55.5% of non-midline cases. The frequency of KIAA1549-BRAF fusion decreased with increasing age, 77% in the age group <20, 54% in the age group 20-40 and 30% in the age group >40.

Conclusion

15-9 and 16-9 KIAA1549-BRAF were the most frequently occurring fusions dominantly seen in the midline. The presence of fusion is inversely proportional to the age of patients. qRT-PCR is the gold standard technique and FISH assay has moderate concordance with qRT-PCR platform.
LGG-54. Asthma reduces glioma formation by T cell decorin-mediated inhibition of microglia
Authors: Chatterjee Jit , Sanapala Shilpa , Cobb Olivia , Bewley Alice , Cordell Elizabeth , Garbow Joel , Holtzman Michael , Gutmann David
Published: June 2022

To elucidate the mechanisms underlying the reduced incidence of brain tumors in children with Neurofibromatosis type 1 (NF1) and asthma, we leverage optic pathway glioma (Nf1-OPG) mice, human and mouse RNAseq data, and two different experimental asthma models. Following ovalbumin or house dust mite asthma induction at 4-6 weeks of age (WOA), Nf1-OPG mouse optic nerve volumes and proliferation are decreased at 12 and 24 WOA, indicating no tumor development. This inhibition is accompanied by reduced expression of the microglia-produced optic glioma mitogen, Ccl5. Human and murine T cell transcriptome analyses reveal that inhibition of microglia Ccl5 production results from increased T cell expression of decorin, which blocks Ccl4-mediated microglia Ccl5 expression through reduced microglia NFκB signaling. Decorin or NFkB inhibitor treatment of Nf1-OPG mice at 4-6 WOA inhibits tumor formation at 12 WOA, thus establishing a potential mechanistic etiology for the attenuated glioma incidence observed in children with asthma.
LGG-63 MEK inhibitor-associated retinopathy (MEKAR) in a pediatric patient with an optic pathway glioma
Authors: Bendel Anne , Skrypek Mary , Johnson Heather , Pribila Jonathan
Published: June 2022

Pediatric low-grade glioma (LGG) and plexiform neurofibroma (PN) universally have up-regulation of the RAS-mitogen-activated protein kinase (MAPK) pathway. Recent phase I and II clinical trials evaluating MEK inhibitors for the treatment pediatric LGG and PN report efficacy and tolerable side effects, including no reported ophthalmologic toxicity. Contrary to the pediatric experience, adult trials using MEK inhibitors describe several ophthalmologic side effects, including MEK inhibitor-associated retinopathy (MEKAR), also termed central serous-like retinopathy. MEKAR is defined as accumulation of subretinal fluid. It occurs in up to 90% of adults on MEK inhibitors, usually causing minimal to no symptoms, and typically resolving without MEK inhibitor dose adjustment. We report a case of MEKAR in a 15 year old boy with an optic pathway pilocytic astrocytoma with duplication of BRAF (7q34). Baseline ophthalmic exam showed 20/20 vision in his right eye with loss of the temporal hemifield and no light perception vision in the left eye. Nine months into treatment with Selumetinib his ophthalmologic exam and optical coherence tomography (OCT) showed asymptomatic bilateral subretinal fluid. Selumetinib was held for 2 weeks resulting in resolution of the subretinal fluid. Selumetib was resumed at the prior dose and MEKAR recurred 2 weeks later but then permanently resolved 4 weeks later despite remaining on Selumetib. Review of the literature discovered a single publication of 2 pediatric patients with optic pathway glioma who developed MEKAR around 6-7 months after initiating Selumetinib, which resolved after stopping Selumetinib. One patient was symptomatic and despite resolution of symptoms, Selumetinib was not resumed. The other patient was asymptomatic and resumed Selumetib, but redeveloped MEKAR 8 months after restarting Selumetinib. Based on adult experience and the limited pediatric experience outlined above, we recommend pediatric patients with asymptomatic and mild-moderate symptomatic MEKAR undergo close monitoring without Selumetinib dose interruption or modification unless symptoms progress.
MEDB-01. Management of the risk of medulloblastoma associated to familial adenomatous polyposis and dysregulated Wnt signalosome
Authors: Abdelmoula Balkiss , Abid Fatma , Karra Amir , Kammoun Sonda , Aloulou Samir , Abdelmoula Nouha Bouayed
Published: June 2022

APC is the key gene of the familial adenomatous polyposis (FAP). This tumor suppressor gene functions by negatively regulating the β-catenin protein and the majority of APC mutations disrupt the β-catenin degradation complex signalosome leading to the activation of the canonical Wnt pathway. Pathogenic APC mutations were reported in association to medulloblastoma. In this study, we report rare mutations of the APC gene detected in Tunisian families from the governorate of Sfax presenting clinically with various digestive and extra-digestive manifestations. Our goal was to assess the oncogenic risks encountered by our pediatric carriers to offer an accurate genetic counselling, particularly at the neurologic level. Molecular investigation of all members of two families was conducted, using bidirectional sequencing of all 15 exons of the APC gene. A phenotype-genotype correlation was conducted to elucidate the mutational pathophysiological mechanism. Two rare mutations were revealed in our familial study. The first mutation was located at exon 13 and was a missense mutation at codon 1690. The second mutation was a deletion identified at codon 4652 in exon 15. The mutations resulted both in truncated gene products. Clinical manifestations closely depending on the position of the mutation were respectively colic polyposis for the first mutation and soft tissue fibromatous tumors for the second. The localization of the APC mutations allows better targeting of surveillance for clinical manifestations that may be included in FAP. Mutations that remove the Axin-binding sites, as is the case for the first mutation, lead to severe clinical pictures whereas mutations that retain one or two of the Axin binding sites are associated with other features such as desmoid tumors. The risk of the Wnt- medulloblastoma subtype, higher among patients with FAP should be considered with a more awareness of signs and symptoms related to CNS tumors in the FAP context.
MEDB-18. Elongation control of mRNA translation supports Group 3 medulloblastoma adaptation to nutrient deprivation
Authors: Delaidelli Alberto , Yao Betty , Wang Que Xi , Huang Yue Zhou , Negri Gian Luca , Hughes Christopher , Zhang Haifeng , Leprivier Gabriel , Sorensen Poul
Published: June 2022

Group 3 affiliation and MYC genetic amplification are associated with poor life expectancy and substantial morbidity in children suffering from medulloblastoma (MB). However, the high metabolic demand induced by MYC-driven transformation sensitizes MYC-overexpressing MB to cell death under conditions of nutrient deprivation (ND). Additionally, MYC-driven transformation is known to promote mitochondrial oxidative phosphorylation (OXPHOS). We previously reported that eukaryotic Elongation Factor Kinase 2 (eEF2K), the master regulator of mRNA translation elongation, promotes survival of MYC-overexpressing tumors under ND. Interestingly, eEF2K is overexpressed in MYC-driven MB and our preliminary proteomics data highlight large-scale alterations in OXPHOS components affecting eEF2K deficient MB cells. We therefore hypothesized that eEF2K activity is required for the selective translation of mRNAs needed for efficient OXPHOS, and for the progression of MYC-driven MB. We pefrormed Multiplexed enhanced Protein Dynamic Mass Spectrometry in eEF2K knockdown MYC-overexpressing D425 MB cells to identify mRNAs selectively translated upon eEF2K activation. Messenger RNAs encoding multiple (9 out of 10 detected) components of the mitochondrial OXPHOS pathway are selectively translated upon eEF2K activation. Inactivation of eEF2K by genetic KO leads to the disassembly of electron transport chain (ETC) complexes I-IV without affecting mRNA levels of their respective components. Consistently, eEF2K KO MB cells display decreased mitochondrial membrane potential and 20% increased proton leak thorough the mitochondrial membrane. In addition, eEF2K inactivation results in increased Group 3 MB cell death under ND and doubles survival of MB bearing mice fed with calorie restricted diets (p< 0.05).Control of mRNA translation elongation by eEF2K is critical for mitochondrial ETC complex assembly and efficient OXPHOS in MYC-overexpressing MB, likely representing an adaptive response by which MYC-driven MB cells cope with acute metabolic stress. Future therapeutic studies will aim to combine eEF2K inhibition with caloric restriction mimetic drugs as eEF2K activity appears critical under metabolic stress conditions.
MEDB-34. A very rare case: medulloblastoma relapse with bone marrow infiltration in a toddler
Authors: Zinke Claudia , Fleischhack Gudrun , Hauer Julia , Lange Björn Sönke , Dörnemann Jenny , Hahn Gabriele , Schackert Gabriele , Gurtner Kristin , Meinhardt Matthias , Jöhrens Korinna , Knöfler Ralf
Published: June 2022

We report about a female toddler congenitally deaf and diagnosed with a non-metastatic desmoplastic medulloblastoma (SHH activated, TP53-wt, variant in LDB1 gene). No tumor predisposition syndrome was found. After complete tumor resection the patient was treated according to I-HIT-MED-Guidance protocol. Five months later an asymptomatic localised relapse (same histology, PTEN frameshift deletion, TERT mutation, LDB1 mutation) detected by routine MRI was treated by complete resection, craniospinal irradiation and an antiangiogenic regimen adapted from the MEMMAT scheme including fenofibrate, thalidomide, celecoxib, topotecan, temozolomide, bevacizumab and intraventricular cytarabine. Before start of systemic treatment blood cell counts were normal. In the second cycle we had to interrupt chemotherapy due to a leukopenia while continuing the antiangiogenic treatment. In order to avoid relevant bone marrow toxicity chemotherapy doses were reduced. Nevertheless we had to stop the fourth cycle because of a severe pancytopenia. Same time the girl presented with fever, neck and leg pain. A full blood count showed: hemoglobin 6.92 g/dl, leukocytes 640/µl, platelets 8,000/µl. Suspecting an infection supported by the presence of a high CrP value of 230 mg/l the patient was treated with i.v. antibiotics. MRI showed an unspecific retropharyngeal soft tissue augmentation, a pleural effusion and high T2 signals in multiple vertebral bodies but no central tumor relapse. The bone marrow diagnostics revealed a diffuse medulloblastoma cell infiltration with the known PTEN frameshift deletion and LDB1 mutation. The liquor was tumor-cell free. We report on an extremely rare case of an early local relapse of desmoplastic medulloblastoma progressing to a diffuse bone marrow infiltration in a toddler. The girl died due to therapy resistance 9 weeks after bone marrow relapse. It remains unclear whether the fatal course was related to the hereditary deafness syndrome and the molecular alterations of the tumor.
MEDB-45. Functional genomics identifies epigenetic regulators as novel therapeutic targets for sonic hedgehog medulloblastoma
Authors: Tsiami Foteini , Piccioni Federica , Root David , Bandopadhayay Pratiti , Segal Rosalind , Tabatabai Ghazaleh , Merk Daniel
Published: June 2022

Medulloblastoma (MB) is among the most common malignant childhood brain tumors that comprises a group of four molecularly distinct diseases. A significant proportion of these tumors is characterized by aberrant activation of the canonical sonic hedgehog (SHH) signaling pathway. Although small-molecule inhibitors targeting Smoothened (SMO) have proven a promising treatment approach for SHH-MB subgroup, primary or acquired resistance impedes its clinical efficacy. Therefore, novel targeted approaches are urgently needed to improve therapeutic strategies for this tumor entity. Here, we conducted a genome-wide CRISPR/Cas9 knockout screen in a murine and a human SHH-MB cell line, SMB21 and DAOY, respectively, in order to decipher tumor-specific genetic dependencies. Our data demonstrate that SMB21 cells highly depend on positive regulators of the SHH pathway, such as Smo and Gli1 for their survival, as opposed to DAOY cells, suggesting that the latter does not represent a faithful model of SHH-MB. Members of the epigenetic machinery such as Dnmt1 and Smarca5 scored strongly as SMB21-context specific essentialities. Pharmacologically, we show that DNMT1 inhibition is efficacious at clinically relevant concentrations against SMO inhibitor- sensitive, as well as resistant SHH-MB cell lines, indicating novel therapeutic avenues for SHH-MB. By performing RNA sequencing of SMB21 cells, we identified early and late changes in global gene expression induced by DNMT1 inhibition, including decreased expression of mediators of SHH signaling, such as Gli1 and Gli2. Of note, gene set enrichment analysis revealed that DNMT1 inhibition downregulates top gene sets associated with cell cycle progression, corroborating the screening results that Dnmt1 is essential for SMB21 proliferation. Further global DNA methylation profiling in SMB cells will help to define the molecular basis of sensitivity to DNMT1 inhibitors in SHH-MB. Summarizing, our data highlight the potential of inhibitors targeting epigenetic regulators in SMO inhibitor- sensitive and resistant MB for more efficacious treatment options.
MEDB-48. Infant medulloblastoma - SHH subtype – with residual disease. To treat or not to treat
Authors: Dahl Christine , Depani Sarita , Hedges Kriti , Aguirregomezcorta Fernando , Aquilina Kristian , Jeelani Owase , Carney Olivia , Sudhakar Sniya , Loebel Ulrike , d′Árco Felice , Mankad Kshitij , Hargrave Darren , Jorgensen Mette
Published: June 2022

Management of infant medulloblastoma remains a challenge. Front-line chemotherapy can successfully avoid radiation in low-risk infant medulloblastoma. Patients that do relapse can be salvaged long-term with radiotherapy. We report 4 cases of infants with medulloblastoma treated with chemotherapy (HIT2000 protocol) with residual or progressive disease. RESULTS: Four cases of infant medulloblastoma, all MBEN/nodular desmoplastic SHH type B, p53 WT, no MYC / MYCN amplification. CASE 1: 16 month old girl, metastatic lesions in the cerebellum and meningeal enhancement. Germline SUFU mutation. After 3 cycles of chemotherapy MRI showed more enhancement of the residual disease. To inform management, second look surgery was performed. Pathology showed fibrous tissue only, no malignant cells. The child continues to be treated as per HIT2000. CASE 2: 5 month old girl, metastatic lesions in the cerebellum. Germline SUFU mutation. 2 months after end of treatment, MRI demonstrated progression of cerebellar lesion. Surgical resection was performed, pathology showed differentiated mature neuronal tissue. No further treatment; remains in remission 1 year after suspected progression. CASE 3: 27 month old boy, metastatic lesions in cerebellum. Germline SUFU mutation. 1 month post-completion of treatment progressive prominent nodules along the cerebellum and cerebellar leptomeningeal enhancement. Biopsy not feasible so close MRI surveillance was initiated. MRI remains stable 1 year after suspected progression. CASE 4: 30 months old boy, non-metastatic disease. Complete resection. No germline mutation. End-of-treatment MRI showed subtle new intraspinal leptomeningeal deposits and a suspicious left optic tract nodule, subsequent MRI 8 weeks later showed clear progressive disease. Unfortunately, the child died before radiotherapy could be delivered. CONCLUSION: Salvage radiotherapy for infants with medulloblastoma who progress following chemotherapy treatment can be life-saving but risk significant cognitive impairment. Differentiation of medulloblastoma following radio/chemotherapy has been reported. We recommend considering tissue confirmation prior to embarking on further treatment for suspected relapse.
MEDB-50. Assessment of cellular radiosensitivity and DNA repair in medulloblastoma cell lines and patient-derivded xenograft slice cultures
Authors: Feyerabend Simon , Rieckmann Thorsten , Riepen Britta , Oetting Agnes , Christiansen Sabrina , Schoof Melanie , Hardt Annika , Köcher Sabrina , Neumann Julia , Schwarz Rudolf , Mack Norman , Schwalm Benjamin , Federico Aniello , Milde Till , Kool Marcel , Schüller Ulrich , Rutkowski Stefan , Petersen Cordula , Rothkamm Kai , Mynarek Martin , Struve Nina
Published: June 2022

Medulloblastoma (WHO grade 4) is the most common malignant brain tumor of childhood. Despite the high importance of radiotherapy for disease control, the mechanisms underlying response and resistance to radiotherapy are incompletely understood. Therefore, we assessed the radiosensitivity and DNA repair capacity of medulloblastoma cell lines in-vitro and of patient-derived xenograft (PDX) models ex-vivo. Cell survival after irradiation of seven medulloblastoma cell lines displaying different subgroups was assessed via colony formation assay (DAOY, UW228, UW473, SJMM4, ONS-76, HDMB-03, D283). The ONS-76 and the mouse SJMM4 cell line were the most radioresistant strains (surviving fraction after 6 Gy (SF6): 0.33 and 0.31, respectively), followed by UW473, UW 228 and DAOY cells (SF6 0.16-0.21). The non-WNT/non-SHH-activated cell lines HDMB-03 and D283 cells demonstrated profoundly higher cellular radiosensitivity (SF6 <0.05). Analysis of residual (24h after irradiation) DNA double-strand breaks (DSB) as assessed by co-localized γH2AX/53BP1-foci demonstrated a significant correlation between DSB repair capacity and cellular survival. To use a more reliable pre-clinical model for medulloblastoma, we further examined DNA repair foci in ex-vivo irradiated slice cultures of PDX models MED-113 (SHH) and NCH2194 & HT028 (Gr. 3). Immunofluorescence analyses of frozen sections demonstrated non-hypoxic (pimonidazole-negative) and proliferating (EdU-positive) cells at the outer rim of the tumor slices. Two hours after irradiation all three PDX models showed a strong increase in 53BP1-foci, clearly indicating DNA damage induction. Most radiation-induced DSB were repaired after 24h. In a first radiosensitization approach, we treated the HT028 model with the PARP inhibitor olaparib (1µM ± 2Gy irradiation). Twenty-four hours after treatment the sample displayed a strong increase in the amount and size of 53BP1-foci, indicating compromised DNA repair. Further in-vitro and ex-vivo investigations with the aim to predict individual radiosensitivity and effective radiosensitization strategies are ongoing.
MEDB-51. Impact of residual tumor on outcomes in children and adolescents with medulloblastoma in the German HIT-cohort
Authors: Wolgast Stella , Obrecht Denise , Mynarek Martin , Bison Brigitte , Schwarz Rudolf , Pietsch Torsten , Kortmann Rolf-Dieter , Warmuth-Metz Monika , Rutkowski Stefan
Published: June 2022

INTRODUCTION: To date, a historical threshold of 1.5cm2 extent of resection (EOR) of the primary tumor is used for risk stratification in pediatric medulloblastoma (MB). METHODS: Data of n=348 patients with MB included into the German HIT-MED studies and registries from 2000-2017 were retrospectively analyzed. Kaplan-Meier statistics and Cox regressions were calculated to determine the influence of EOR, histological and molecular subtype, MYC/N-amplification and presence of metastases at first diagnosis on overall and progression-free survival (OS/PFS). ROC curves were calculated aiming at identifying a new EOR cut-off. RESULTS: Median age at diagnosis was 6.8 [0.1-20.5] years. After initial surgery, residual tumor (R) ≥1.5cm2 was present in 129/348 patients (37%). 57% presented with additional metastases. In most cases, classic histology was found (71%, DMB/MBEN: 20%, LC/AMB: 9%). Molecular subtype was nonWNT/nonSHH in 68% (Group 4: 37%, Group 3: 31%), WNT in 6% and SHH-activated types in 26% of evaluated cases (n=208). MYC/MYCN-amplification was present in 5 and 4%, respectively. 41/348 patients received additional surgery, resulting in 73% GTR (not reported: n=22). EOR had no significant impact on OS/PFS (GTR: 5y-OS/PFS 69.9±3.4/57.6±3.7%, STR: 5y-OS/PFS 71.4±4.1/56.2±4.5%, p=0.6/0.8; Cox: p=0.2/0.4; median follow-up 8.4 [0.1-18.0] years). ROC curves did not identify a significantly improved limit for outcome-relevant EOR cut-off. Analyses confirmed less favorable OS/PFS for patients with metastatic disease (p=0.04/p<0.05), LC/AMB (p<0.05/p<0.05), Group 3 (p<0.05/p<0.05), and MYC-amplification (p<0.05/p<0.05). Cox regression confirmed an increased risk for Group 3 (OS: HR=4.74, p<0.05, PFS: HR=2.90, p<0.05) and M+ (PFS: HR=2.69, p<0.05). DISCUSSION: No distinct influence of EOR </≥1.5cm2 on OS/PFS in pediatric MB was detected. The relevance of EOR and the historical limit of 1.5cm2 should be further investigated in distinct MB subtypes and in context of other risk factors.
MEDB-85. Transcriptional complexes as resistance drivers to BET inhibition
Authors: Boynton Adam , Lupien Leslie , Kumbhani Rushil , Gionet Gabrielle , Chacon Madison , Goodale Amy , Root David , Keshishian Hasmik , Robinson Margaret , Carr Steven , Bandopadhayay Pratiti
Published: June 2022

BET-bromodomain inhibition (BETi) is a promising therapeutic strategy to target MYC-driven cancers, including Group 3 medulloblastoma, a deadly childhood brain tumor. We have shown that BET inhibitors exhibit preclinical efficacy against MYC¬-amplified medulloblastoma, providing motivation to evaluate this drug class in early phase clinical trials. However, our work has also found that MYC-amplified medulloblastoma cells can acquire resistance to BETi, suggesting that curative responses for this disease will require combination therapy. To guide the development of such combination therapies, we have focused our efforts on elucidating the mechanisms through which medulloblastoma cells acquire resistance to BETi. We found that medulloblastoma cells can develop tolerance to BETi by reinstating the expression of cell-essential “rescue genes,” which include bHLH transcription factors, cell-cycle regulators, and anti-apoptosis genes. This transition to the resistant cell state is mediated through changes in chromatin structure including the upregulation of H3K4me3 promoters. Our preliminary results suggest that BETi-resistant cells maintain mRNA transcription and protein translation of important mediators of resistance. Importantly, we observe that BETi-resistant medulloblastoma cells are more dependent on specific protein complexes involved in transcriptional regulation. This project explores the mechanisms through which these transcriptional regulators help maintain transcription of rescue genes that drive BETi resistance and evaluates the potential of targeting these drivers of BETi resistance. These results will help guide the development of combination approaches to improve the efficacy of BETi for the treatment of MYC-driven medulloblastoma.
NFB-08. TRAM-01: A Phase 2 study of trametinib for pediatric patients with neurofibromatosis type 1 and plexiform neurofibromas
Authors: Kiaei Dorsa Sadat , Larouche Valérie , Décarie Jean-Claude , Tabori Uri , Hawkin Cynthia , Lippé Sarah , Ellezam Benjamin , Ospina Luis H , Théoret Yves , Desjardins Léandra , Métras Marie-Élaine , Sultan Serge , Cantin Édith , Routhier Marie-Ève , Mailloux Chantal , Bertrand Marie-Claude , Caru Maxime , Vairy Stéphanie , Legault Geneviève , Bouffet Éric , Ramaswamy Vijay , Coltin Hallie , Lafay-Cousin Lucie , Hukin Juliette , Erker Craig , Jabado Nada , Dehaes Mathieu , Perreault Sébastien
Published: June 2022

BACKGROUND: Plexiform neurofibromas (PN) are found in up to 50% of patients with neurofibromatosis type 1 (NF1). Trametinib has been used widely to treat PN but limited data has been reported on its efficacy within a clinical trial. METHODS: This ongoing multicenter phase II trial includes patients with pediatric low-grade glioma and PN. The primary objective for PN was to evaluate the overall response rate based on RECIST 1.1 criteria after daily oral trametinib administration for eighteen 28-day cycles. The volumes of PN were centrally quantified using a new semi-automatic 3D segmentation method. RESULTS: As of January 1, 2022, 45 patients with PN were enrolled in the study. Twenty-eight completed treatment and were available for analysis. For these patients, the median age was 11.4 years (range 0.7-19.8) including 16 males (57.1%). The majority did not receive prior systemic therapies (71.4%). The median volume of PN at baseline was 49.5 cm3 (range 2.6 to 469). Among the 28 patients, 25 (89.3%) completed 18 cycles as planned. One patient discontinued due to adverse reaction, one patient refused to continue treatment and one patient discontinued treatment based on physician decision. Median duration of treatment was 15.9 months (range 4.6 to 16.8). Median duration of follow-up was 29.7 months (range 17.7 to 38.1). A total of 32 PN were available for volumetric analysis. Using RECIST evaluation, the overall response rate was 24.1%. Volumetric assessment demonstrated an overall response rate of 60.7% and 62.5% of PN showed a decrease of more than 20% in volume. Median decrease in volume was -30% (range -93.5 to 14.3). Twenty-seven patients (93.1%) had durable response without progression (lasting ≥1 year). CONCLUSION: We report outcome and volumetric quantification of PN treated with trametinib within a large clinical trial. Based on the current results, trametinib appears effective and offers durable response.
NFB-18. Integration of single-nuclei RNA-sequencing and spatial transcriptomics to define the complex tumor microenvironment of NF1-associated plexiform neurofibroma and highly-aggressive malignant peripheral nerve sheath tumors
Authors: Amani Vladimir , Donson Andrew , Riemondy Kent , Fu Rui , Willard Nicholas , Gilani Ahmed , Norris Gregory , Griesinger Andrea , Harris Faith , Grimaldo Enrique , Foreman Nicholas
Published: June 2022

During formation of plexiform neurofibroma (PN), a complex tumor microenvironment (TME) develops, with recruitment of other cell types being critical for growth and progression. Approximately 10% of PN can undergo transformation into malignant peripheral nerve sheath tumors (MPNST) which is a substantial cause of mortality in older teenagers and young adults. We sought to apply single cell transcriptomic analysis to PN and MPNST to provide a clearer understanding of the complex TME and how this contributes to transformation and disease progression. Due to the cohesive cellularity of PN, single-cell RNA-sequencing is difficult and may result in a loss of detection of critical cellular subpopulations. Single-nuclei RNA-sequencing (snRNA-seq) is an alternative approach that can be applied to fibrous and bulk frozen tissues, such as NF1-associated PN. Our initial snRNA-seq analysis of PN indicates that PN have a TME comprised of a variety of cellular subpopulations, with the predominant fraction being fibroblast-like cells. snRNA-seq analysis of MPNST also shows high cellular heterogeneity, including distinct fibroblast-like subpopulations distinct from PN fibroblast clusters, increased proliferating populations and antigen presenting cells. MPNST cluster separately from PN, suggesting an evolutionary shift in tumor biology. We are currently validating our findings using Visium spatial transcriptomic profiling, allowing us to apply TME architectural context to the PN and MPNST subpopulations identified by snRNA-seq. These techniques provide a deeper understanding of the complex cellular heterogeneity of human PN and MPNST that has not previously been used to describe the TME of these tumors. The mechanisms of tumorigenesis and malignancy described can provide targets for novel therapies ultimately benefitting patients with these devastating tumors of childhood and early adulthood.
QOL-07. The importance of an onco-fertility program for pediatric neuro-oncology patients
Authors: IJgosse Irene , Looijenga Leendert , Klijn Aart , Oude-Ophuis Ralph , van den Heuvel Marry , Veening margreet , Bos Annelies , Broer Simone , van Leeuwen Jeanette , van der Steeg Lideke , van de Wetering Marianne
Published: June 2022

INTRODUCTION: In the Netherlands pediatric oncology care is centralized in one hospital since 2018. 600 new patients a year are seen with 100-120 new neuro-oncology (NO) patients. Of the NO patients 20-25% classify as high risk for infertility (HR) such as patients with medulloblastoma, ependymoma, ATRT and germinoma . An onco-fertility program was started navigated by a nurse-practitioner. The program runs with intense collaboration between the different specialties. All new patients are identified according to the international guidelines on fertility care. The fertility-risk is based on the CED score (cyclofosfamide equivalent dose) and radiotherapy dose. Since 2018 awareness was created by teaching sessions among colleagues, nursing staff, and parent association organizations. METHODS: All HR children are informed by the nurse-practitioner and can be referred for counseling to gynaecology for OTC (ovarian tissue cryopreservation) or urology for sperm cryopreservation or testicular biopsy. Monthly the onco-fertility working-group members discuss cases and research in the field. RESULTS: In 2019, 19% NO cases and in 2020 18% of cases were HR for infertility. In both years 36% of these cases had fertility preservation performed. In 2021, 22% cases HR were identified and in 55% preservation was performed. Reasons for not preserving fertility were diverse, varying from poor prognosis, or too ill to be included. CONCLUSION: Awareness of the fertility risk in NO patients who are HR is necessary. These patients need to be informed, and stratified for counseling and offered fertility preservation before start of their treatment. An active onco-fertility program helps to offer the best option for future fertility for these patients
QOL-16. A 6-year longitudinal study of neurocognition in children treated for a brain tumor
Authors: Bullens Kristien , Sleurs Charlotte , Van den Wyngaert Linde , Vandenabeele Karen , Vercruysse Trui , Claeys Laura , Prikken Sofie , Jacobs Sandra , Lemiere Jurgen
Published: June 2022

Long-term neurocognitive difficulties in children treated for a brain tumor are well documented and known to be affected by treatment. However, longitudinal studies of these neurocognitive difficulties are scarce. In the present study, we investigated the impact of radiotherapy (RT) on the evolution of neurocognition between different consecutive time points after diagnosis, and throughout treatment and survivorship. This study included 69 children diagnosed with a brain tumor at the University Hospitals Leuven who completed a comprehensive neuropsychological test battery (intelligence, memory, visuomotor functioning, and QoL) on at least three consecutive time points (2-year interval). Of all patients, 40 completed the test battery at 4 time points. The first assessment was conducted at the earliest possible moment after diagnosis and before the start of any adjuvant therapy. Mean age at diagnosis and first assessment were 7.75 and 7.92 years, respectively. The most common diagnoses were pilocytic astrocytoma (n=33) and medulloblastoma (n=11). 29.0% of the children received local RT and 15.9% received craniospinal RT. A repeated measures analysis with cranial irradiation (no, focal, craniospinal) as between-subjects factor and age at diagnosis as covariate demonstrated a significant interaction effect between time and type of irradiation for both overall intelligence (p=0.007) and QoL (p=0.006) for children with three and four assessments. Children who received craniospinal irradiation demonstrated a significant decline in overall intelligence and a significant worsening of QoL. For the non-irradiated group, an improvement of QoL was observed. For processing speed, a significant time effect was found for children with three and four assessments (p<0.001), with a significant improvement for the overall group. The results of this longitudinal study demonstrated diverse longitudinal trajectories. Children who received craniospinal irradiation are most often confronted with intellectual decline and worsening of QoL.