High-grade Neuroepithelial Tumor Research Articles

드문 뇌실 내 종양 수술 경험에 대한 증례 보고

In this case report, we present a rare case of a suspicious central nervous system (CNS) high-grade neuroepithelial tumor with BCOR alteration (CNS HGNET-BCOR). A 29-year-old woman ini-tially presented with an incidental ventricular tumor detected on computed tomography. The brain magnetic resonance imaging revealed a 6 × 5 cm heterogeneously enhancing solid cystic mass with coarse calcifications in the right lateral ventricle. Preoperative radiological diagnosis suggested a cen-tral neurocytoma, and subsequent surgery was done in gross total resection with satisfactory recov-ery. However, after three years, tumor recurrence was observed, leading to revision surgery. Based on the histopathological evaluation according to the 2021 World Health Organization classification, the tumor was suggested as CNS HGNET-BCOR. Adjuvant radiotherapy was planned as part of the treatment strategy. This case report contributes to the limited knowledge about intraventricular CNS HGNET-BCOR tumors, offering insights into diagnosis and treatment approaches for this rare en-tity.

Pediatric-type high-grade neuroepithelial tumors with CIC gene fusion share a common DNA methylation signature

Pediatric neoplasms in the central nervous system (CNS) show extensive clinical and molecular heterogeneity and are fundamentally different from those occurring in adults. Molecular genetic testing contributes to accurate diagnosis and enables an optimal clinical management of affected children. Here, we investigated a rare, molecularly distinct type of pediatric high-grade neuroepithelial tumor (n = 18), that was identified through unsupervised visualization of genome-wide DNA methylation array data, together with copy number profiling, targeted next-generation DNA sequencing, and RNA transcriptome sequencing. DNA and/or RNA sequencing revealed recurrent fusions involving the capicua transcriptional repressor (CIC) gene in 10/10 tumor samples analyzed, with the most common fusion being CIC::LEUTX (n = 9). In addition, a CIC::NUTM1 fusion was detected in one of the tumors. Apart from the detected fusion events, no additional oncogenic alteration was identified in these tumors. The histopathological review demonstrated a morphologically heterogeneous group of high-grade neuroepithelial tumors with positive immunostaining for markers of glial differentiation in combination with weak and focal expression of synaptophysin, CD56 and CD99. All tumors were located in the supratentorial compartment, occurred during childhood (median age 8.5 years) and typically showed early relapses. In summary, we expand the spectrum of pediatric-type tumors of the CNS by reporting a previously uncharacterized group of rare high-grade neuroepithelial tumors that share a common DNA methylation signature and recurrent gene fusions involving the transcriptional repressor CIC. Downstream functional consequences of the fusion protein CIC::LEUTX and potential therapeutic implications need to be further investigated.

Pediatric BCOR-Altered Tumors From Soft Tissue/Kidney Display Specific DNA Methylation Profiles

In the pediatric population, BCL6-correpresor gene (BCOR)–upregulated tumors include primitive myxoid mesenchymal tumors/undifferentiated sarcomas (PMMTI/UND), clear cell sarcomas of the kidney (CCSK), and high-grade neuroepithelial tumors (HG-NET). We investigated DNA methylation (DNAm) and copy number variation (CNV) profiling in these tumors (N = 34) using an Illumina EPIC BeadChip to better define the potential use of these tools to confirm diagnosis and predict outcomes. Twenty-seven tumors from 25 patients (age range, 0-10 years), showed molecular confirmation of genetic abnormalities as follows: BCOR internal tandem duplication in 14 PMMTI/UND, 8 CCSK, and 3 HG-NET and YWHAE fusions in 2 PMMTI/UND. The remaining 7 cases lacking informative molecular data were analyzed by immunophenotyping and were included in the study as a training cohort, clearly separated from the main study group. These were 4 PMMTI, 1 HG-NET, and 1 CCSK in which poor RNA preservation precluded the confirmation of BCOR rearrangements and 1 CCSK in which no rearrangements were found. DNAm data were compared with those of brain tumor and/or sarcoma classifier. Differentially methylated regions (DMRs) were analyzed in the 3 groups. Twenty-two cases of the 24 molecularly confirmed PMMTI/UND and CCSK and 3 of 6 of those with only immunophenotyping were classified within the methylation class “BCOR-altered sarcoma family” with optimal calibrated scores. PMMTI/UND and CCSK showed similar methylation profiles, whereas thousands of DMRs and significantly enriched pathways were evident between soft tissue/kidney tumors and HG-NET. The CNV analysis showed an overall flat profile in 19 of the 31 evaluable tumors (8/10 CCSK; 9/18 PMMTI/UND; 2/4 HG-NET). The most frequent CNVs were 1q gain and 9p and 10q loss. Follow-up time data were available for 20 patients: ≥2 CNV significantly correlated with a worse overall survival rate. In conclusion, soft tissue and kidney BCOR sarcomas matched with BCOR-altered sarcoma methylation class, whereas those from the brain matched with the central nervous system tumor classifier HG-NET BCOR, supporting the notion that DNAm profiling is an informative diagnostic tool. CNV alterations were associated with a more aggressive clinical behavior.

The spectrum of morphological findings in pediatric central nervous system MN1-fusion-positive neuroepithelial tumors.

Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS-HGNET-MN1) is a rare entity defined by its DNA methylation pattern and pathologically considered to be high-grade with mixed patterns, stromal hyalinization, and with astrocytic differentiation. Our aim was to present six pediatric cases to contribute to the characterization of this group of tumors. Six female patients aged 4 to 12years with CNS tumors with MN1 alteration identified using genome-wide methylation arrays and/or RT-PCR were included. Clinicopathological, morphological, immunohistochemical, and molecular findings were analyzed. Tumor location was the parietal lobe in four and the intramedullary spinal cord in two.Two were morphologically diagnosed as ependymomas, one as gliofibroma, one as a HGNET-MN1 altered and the other two were difficult to classify. All were well-defined tumors, with a cysticcomponent in three. Only two tumors had extensive stromal hyalinization, three hadpseudopapillary formations, and four had other patterns. Multinucleated, clear, and rhabdoidcells were present. Necrosis and histiocyte clusters were also observed. Proliferative indexwas >10 in four. GFAP, EMA, CK, and SYN were variable, while Olig2 staining was mostly positive.Four of six patients with supratentorial tumors and complete resections were alive and tumor freeafter 2 to 10 years of follow-up. The two cases with medullary involvement and incompleteresections were alive and undergoing treatment 2 years after surgery. Neuroepithelial-MN1 tumors are challenging and suspicion requires molecular confirmation. Our pediatric data contribute to the knowledge for accurate diagnosis. Although further studies with a larger number of cases should be conducted in order to draw more robust conclusions regarding clinico-pathological features, here we present valuable pediatric data to increase the knowledge that may lead to the accurate management of this group of tumors.

CNS Tumor with BCOR Internal Tandem Duplication: The First Case in Southeast Asia

The central nervous system (CNS) tumor with BCOR internal tandem duplication (ITD) or high-grade neuroepithelial tumor with BCOR alterations (HGNET-BCOR) has been proposed as a new entity of CNS embryonal tumor. We report herein the first case of CNS tumor with BCOR ITD in Southeast Asia. The patient was a 2-year-old girl who presented with head tilt and ataxia. CNS showed a posterior fossa mass, 5.7x5.2x4.2 cm, with faint enhancement and internal hemorrhage. The lesion was removed, and the pathological examination revealed a hypercellular tumor comprising neoplastic cells with oval hyperchromatic nuclei. Perivascular pattern was occasionally observed. Pseudopalisading necrosis was seen but microvascular proliferation was absent. Although the clinical features of HGNET-BCOR are not distinctive and may overlap with other high-grade primary CNS tumors, awareness of the pathological features and the positive BCOR immunostain should lead to a final diagnosis with the identification of BCOR ITD using a molecular method.

Spectrum of paired-like homeobox 2b immunoexpression in pediatric brain tumors with embryonal morphology.

Paired‐like homeobox 2b (PHOX2B) is an established immunomarker for peripheral neuroblastoma and autonomic nervous system cells. We aimed to evaluate the utility of PHOX2B immunostaining in central nervous system (CNS) tumors with embryonal morphology. Fifty‐one tumors were stained with PHOX2B and submitted for whole slide image analysis: 35 CNS tumors with embryonal morphology (31 CNS embryonal tumors and four gliomas); and 16 peripheral neuroblastomas were included for comparison. Diffuse nuclear immunopositivity was observed in all (16/16) neuroblastomas (primary and metastatic). Among CNS embryonal tumors, focal immunoreactivity for PHOX2B was observed in most (5/7) embryonal tumors with multilayered rosettes (ETMR) and a single high‐grade neuroepithelial tumor (HGNET) with PLAGL2 amplification; the remaining 27 CNS tumors were essentially immunonegative (<0.05% positive). Among ETMR, PHOX2B expression was observed in a small overall proportion (0.04%–4.94%) of neoplastic cells but focally reached up to 39% in 1 mm ‘hot spot’ areas. In the PLAGL2‐amplified case, 0.09% of the total neoplastic population was immunoreactive, with 0.53% in the ‘hot spot’ area. Care should be taken in interpreting PHOX2B immunopositivity in a differential diagnosis that includes metastatic neuroblastoma and CNS tumors; focal or patchy expression should not be considered definitively diagnostic of metastatic peripheral neuroblastoma.

Abstract 2491: Molecular and clinical characterization of the new WHO entity ‘Astroblastoma, MN1 altered’ and its molecular subgroups

Abstract Using DNA methylation profiling, already in 2016 we had identified novel molecularly defined CNS tumor entities, including CNS high grade neuroepithelial tumors with MN1 alteration (HGNET-MN1), which have in the recently updated WHO classification of CNS tumors been renamed into Astroblastoma, MN1 altered. However, little is still known about the molecular and clinical characteristics of these tumors. To further molecularly and clinically characterize this unique entity, we collected patient material, clinical information and molecular data from 176 Astroblastoma, MN1 altered tumors, which were all identified based on their characteristic DNA methylation pattern. T-SNE clustering analyses of the DNA methylation data together with our large database of almost 100,000 reference cases showed that this entity forms one main cluster defined by interchromosomal gene fusions of mainly MN1 and BEND2 and a smaller, distinct, but adjacent cluster that mainly showed tumors with MN1:CXXC5 fusions. Comparing molecular data of the BEND2- and CXXC5-fused groups we found that chromosomal copy numbers show distinct patterns, such as 16q loss in one third of cases from the BEND2-fused group, and a gain of chromosome 5 in one third of CXXC5-fused cases. Patients of the BEND2-fused group showed a strong enrichment of female patients (85%), whereas the CXXC5-fused group showed the contrary trend and consisted of 75% male patients. Original histological diagnoses of 110 BEND2-fused cases revealed that most tumors were diagnosed as an Astroblastoma (39%), followed by Ependymoma (20%) and PNET histologies (15%), which is in line with previous findings on Astroblasotma, MN1 altered cases. The CXXC5-fused subset, however, showed a distinct histological distribution and only 1 out of 13 cases (8%) had an Astroblastoma histology in the original report, whereas the other cases were diagnosed as PNET (38%), Ependymoma (23%), HGG (23%), or unknown (8%). Investigations of clinical data revealed that BEND2-fused cases (n=65) show a 5/10 year OS of 97% and 89% and a 5/10 year PFS of 48% and 35%, respectively, which is in line with previous studies in smaller series indicating a favorable overall but unfavorable progression-free survival. The smaller subset of CXXC5-fused patients (n=8) indicated a 5/10 year OS of 83% and a 5/10 year PFS of 60% each. First analyses of BEND2-fused cases indicate that an Astroblastoma histology might be associated with a favorable OS, however further analyses, including a central pathology review, are needed to validate this observation. Citation Format: Felix Schmitt-Hoffner, Johannes Gojo, Monika Mauermann, Katja von Hoff, Martin Sill, Andrey Korshunov, Damian Stichel, Felix Sahm, Natalie Jäger, Stefan Pfister, Marcel Kool. Molecular and clinical characterization of the new WHO entity ‘Astroblastoma, MN1 altered’ and its molecular subgroups [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2491.

HGG-34. Upfront Molecular Targeted Therapy for the Treatment of BRAF-mutant Pediatric High-Grade Glioma

Abstract 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.

PATH-13. Methylation analysis in the diagnosis of pediatric CNS tumors; a single center experience

Abstract BACKGROUND: Tumors of Central Nervous System (CNS) comprise major cause of cancer-related morbidity and mortality during childhood. Recent advances in genome and epigenome research allow for molecular classification of CNS tumors, treatment stratification and therapeutic target identification. In many countries, including Greece, this integrated diagnosis is not possible, yet, in a routine setting due to financial and infrastructural reasons. DESIGN/METHODS: We analyzed the results from the methylation profiling performed on tumor samples from newly diagnosed and selected retrospective patients followed in our unit. Analyses were performed through the PTT2.0 and MNP2.0 Studies, as part of a collaboration project between ACCC (Athens Cancer Comprehensive Center) and DKFZ (German Cancer Research Center). RESULTS: Methylation arrays from 50 patients (mean age: 8years, range: 0-17years) have been analyzed. High calibrated score (&amp;gt;0.9) was achieved in 38 patients (76%) and in 33 (86%) of these, the histological diagnosis matched the methylation class. The remaining 5 cases, diagnosed by the local pathologist as ganglioneuroma, primitive neuroectodermal tumor, anaplastic astrocytoma, pineoblastoma and oligodendroglioma, were classified according to the methylation profiling as dermatofibrosarcoma protuberans, medulloblastoma group 3, high-grade glioma H3.3G34mutant, high-grade neuroepithelial tumor with BCOR alteration and glioneuronal tumor, respectively. Only four cases had no match in the classifier, while seven cases received low score (0.5-0.8). In 6 out of the 7 cases with low score, the diagnosis was confirmed with the use either of the copy-number profile inferred from the methylation array or by additional testing for gene fusions and mutations. In 25 medulloblastomas, methylation profiling provided molecular classification, according to the 2021 WHO Classification. CONCLUSIONS: Our experience on the first 50 cases suggests that methylation array needs to be considered as an integral part of the diagnostic process of pediatric patients with CNS tumors and highlights the importance of international collaboration programs in pediatric neuro-oncology.

HGG-31. Unique case of a bithalamic H3K27-wildtype diffuse midline glioma, EGFR-altered with methylated MGMT

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.

PATH-02. Using DNA methylation profiling to define tumor type and appropriate treatment: a case report and review of the literature of a rare CNS CIC altered sarcoma

The utilization of methylation profiling is increasingly becoming part of the standard evaluation for high-grade malignancies. CNS primary tumors with CIC alteration are a recently recognized CNS tumor entity identified via DNA methylation profiling of primitive neuroectodermal tumors (PNET). PNETs have historically carried a poor overall prognosis; however, CNS tumors with CIC alteration have rarely been described in the literature and much remains to be discovered regarding the presentation, tumor characteristics, outcomes, and ideal treatment strategy to optimize survival in these patients. We describe the case of a 2-year-old Hispanic female with a CNS primary tumor with CIC alteration. This patient initially presented with a five-week history of fatigue, headaches, emesis, and right-sided muscle weakness and was found to have a right-sided supratentorial mixed solid and cystic mass. The initial diagnosis was consistent with a high-grade neuro-epithelial tumor based on histology and standard CNS tumor genetic markers. Due to poorly defined tumor characteristics, a sample was also sent for DNA methylation profiling. The profiling pattern was consistent with a CNS CIC altered sarcoma thereby significantly altering the treatment plan. Accurate diagnosis is critical in managing patients with cancer. DNA methylation profiling has contributed to diagnostic accuracy in these aggressive tumors; however, it also creates challenges with beginning treatment expediently due to the time required for processing and interpretation. This case illustrates the positive utility of DNA methylation to better characterize tumor types and the impact this has on both treatment as well as prognosis.

PATH-12. A new powerful tool to simultaneously deliver DNA methylation profile and driver fusions detection based on Nanopore Sequencing

Abstract The fast advances in molecular biology have led to the discovery of new genetic and epigenetic driver events that play a key role in the pathogenesis of central nervous system (CNS) tumors. These data showed the importance of molecular biology, and in particular methylation profiling and fusion detection, to complete the histological examination. Exploring all these complex genomic and epigenomic alterations with the technologies implemented in the routine diagnosis requires massive laboratory equipment. In addition, it could take weeks before getting data that could be important to adapt the diagnosis, prognosis, and to ultimately guide the treatment’s choice. We describe the innovative potential of a nanopore sequencing device to obtain fast and multiple information to characterize CNS tumors. Adaptive-sampling is a software-controlled enrichment unique method that allows simultaneous methylation profiling, copy number landscape assessment, and fusion gene detection. Thereby, this technology brings comprehensive molecular information that could be very important for CNS tumor classification in a very short delay (below one week) and with a relative low cost compared to the combined other molecular analysis needed to get the same information. We report ten cases of diverse CNS tumors with already known oncogenic structural variants such as YAP1-MAMLD1 fused ependymoma, CNS neuroblastoma with FOXR2 activation, CNS high-grade neuroepithelial tumor with BCOR and MEN1 alteration, and atypical teratoid rhabdoid tumors (ATRT). For these tumors, using adaptive sampling with the nanopore sequencing, we were able to detect fusion genes as driver events, while obtaining at the same time the methylation profile to corroborate the tumor classification. Our results with this combined approach, never described before, demonstrate its feasibility as a new extremely powerful tool and show remarkable perspectives for this technology to bring a fast and comprehensive tumor molecular characterization.

ETMR-01. Management of CNS tumor with BCOR internal tandem duplication with multimodalities therapy: Surgery, Intensive Chemotherapy, and Radiation

The 2021WHO CNS tumor classification includes CNS tumors with internal tandem duplications in the BCL6 corepressor (BCOR) gene as a new entity of CNS embryonal tumors labelled high-grade neuroepithelial tumors with BCOR alterations (HGNET-BCOR) are characterized by genetic aberrations in the BCOR gene located at Xp11.4, leading to increased expression of BCOR mRNA and distinct DNA methylation profiles. currently no agreement on the optimal strategy to manage these rare tumors, which mostly occur in young children These tumors are usually treated as high grade glioma HGG with upfront radiation therapy with poor outcome. We report 2.5 years old boy presenting with headache and vomiting. MRI showed a well-defined left cerebellar mass, hyperintense in T2 and hypointense in T1, with restricted diffusion and no spinal CSF seeding metastases. He underwent gross surgical resection of the tumor initial pathological diagnosis was epithelioid high grade malignant neoplasm. Brain tumor methylation classifier analysis of resected tumor tissue confirmed a CNS tumor with BCOR internal tandem duplication (WHO grade 4). The patient was treated per COG ACNS0334 (3 induction cycles of vincristine, cyclophosphamide, cisplatin, etoposide, HDMTX, followed by consolidation with 3 cycles of carboplatin and thiotepa with autologous hematopoietic stem cell rescue). MRI brain before the start of chemotherapy showed a small recurrent mass within the surgical cavity. post-induction MRI detected stable-sized residual lesion in the surgical cavity; however, post-consolidation MRI showed complete resolution of the residual mass. The patient subsequently received craniospinal irradiation (36 Gy [CSI]) with a boost to the tumor bed up to 54 GY. By the time of writing this report our patient is still in complete remission. Our case showed that this aggressive brain tumor may respond well to intensive multimodalities therapy Further case studies and international prospective trials are needed to optimize the clinical management of these rare tumors.

LINC-03. A single center retrospective analysis of current therapy and outcome of central nervous system tumors in children of Beijing

OBJECTIVE: To explore the clinical characteristics, therapy and outcome in children with central nervous system (CNS) tumors in Beijing, China. METHODS: Clinical data of 1003 patients with newly diagnosed CNS tumors under the age of 15 years admitted to Beijing Shijitan Hospital between January 2017 and December 2021 were retrospectively analyzed. The diagnoses were confirmed by pathology and/or molecular tests. RESULTS: 34 patients were lost to follow up. Medulloblastoma (n=472), ependymoma (n=79), ETMR (n=59) and pinealoblastoma (n=19) were treated according to HIT-2000/2017, 5-year progression-free survival (PFS) and overall survival (OS) were 76.4 ± 2.3%/ 84.8 ±1.9% in MB, 88.8±3.7% /89.5±3.8% in ependymoma, 49.9±7.6%/59.6±10.7% in ETMR, and 3y-PFS/OS of 11.1±10.5%, 90.0±9.5% in pinealoblastoma. The detailed histology of 59 cases of embryonal tumors included 40 cases of CNS embryonal tumor, 9 neuroblastoma, 7 ETMR, and 3 rare tumors (Intracranial mesenchymal tumor with FET-CREB fusion, CNS high-grade neuroepithelial tumor with BCOR alteration, and Melanotic neuroectodermal tumor of infancy). Among 19 cases of pinealoblastoma, two contain DICER1 mutations. Atypical teratoid/rhabdoid tumors (n=36) were treated by EU-RHAB-Protocol with 3y-PFS/OS of 42.2 ± 9.4 % and 62.8 ± 9.5 %. For low-grade gliomas (n=153, 114 cases of OPG and 39 other non-STR/NTR or progressive cases) under SIOP-LGG 2004, 5y-PFS/OS rates were 77.6±5.2% and 92.4±3.2%; Comparatively, among 63 cases of high-grade gliomas, 19 cases survived with median survival of 52 months, 44 cases died. Choroid plexus cancers (n=13) were treated according to CPT-SIOP-2009 with 5y-PFS /OS of 68.4 ± 13.1 % and 64.8±14.3 %. Among 109 germ cell tumors, 5y-PFS/OS were 93.8±2.8% and 95.5±2.2%, respectively. CONCLUSION: The prognosis of CNS tumors are related to pathology, molecular type and individualized therapy. By international multicenter cooperation and adopting advanced protocols, the survival rates of pediatric CNS tumors can be significantly improved.

Central nervous system high-grade neuroepithelial tumor with BCOR alteration: case report

Central nervous system high-grade neuroepithelial tumor with BCOR alteration: case report

Upfront molecular targeted therapy for the treatment of BRAF-mutant pediatric high-grade glioma.

The prognosis for patients with pediatric high-grade glioma (pHGG) is poor despite aggressive multimodal therapy. Objective responses to targeted therapy with BRAF inhibitors have been reported in some patients with recurrent BRAF-mutant pHGG but are rarely sustained. 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. Nineteen patients were identified, with a median age of 11.7 years (range, 2.3-21.4). 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 and overall survival for the cohort were 65% and 82%, respectively, and superior to a historical control cohort of BRAF-mutant pHGG patients treated with conventional therapies. Upfront targeted therapy for patients with BRAF-mutant pHGG is feasible and effective, with superior clinical outcomes compared to historical data. This promising treatment paradigm is currently being evaluated prospectively in the Children's Oncology Group ACNS1723 clinical trial.

Imaging Features with Histopathologic Correlation of CNS High-Grade Neuroepithelial Tumors with a BCOR Internal Tandem Duplication.

A new brain tumor entity occurring in early childhood characterized by a somatic BCL6 corepressor gene internal tandem duplication was recently described. The aim of this study was to describe the radiologic pattern of these tumors and correlate this pattern with histopathologic findings. This retrospective, noninterventional study included 10 children diagnosed with a CNS tumor, either by ribonucleic acid-sequencing analysis or deoxyribonucleic acid methylation analysis. Clinical, radiologic, and histopathologic data were collected. A neuropathologist reviewed 9 tumor samples. Preoperative images were analyzed in consensus by 7 pediatric radiologists. All tumors were relatively large (range, 4.7-9.2 cm) intra-axial peripheral masses with well-defined borders and no peritumoral edema. All tumors showed mild and heterogeneous enhancement and marked restriction on DWI of the solid portions. Perfusion imaging showed a relatively lower CBF in the tumor than in the adjacent normal parenchyma. Nine of 10 tumors showed areas of necrosis, with the presence of hemorrhage in 8/10 and calcifications in 4/7. Large intratumoral macroscopic veins were observed in 9/10 patients. No intracranial or spinal leptomeningeal dissemination was noted at diagnosis. CNS tumors with a BCL6 corepressor gene internal tandem duplication present as large intra-axial peripheral masses with well-defined borders, no edema, restricted diffusion, weak contrast enhancement, frequent central necrosis, hemorrhage and calcifications, intratumoral veins, and no leptomeningeal dissemination at the time of diagnosis. Knowledge of these imaging characteristics may aid in histologic, genomic, and molecular profiling of brain tumors in young children.

Assessment of BCOR Internal Tandem Duplications in Pediatric Cancers by Targeted RNA Sequencing

Alterations in the BCOR gene, including internal tandem duplications (ITDs) of exon 15 have emerged as important oncogenic changes that define several diagnostic entities. In pediatric cancers, BCOR ITDs have recurrently been described in clear cell sarcoma of kidney (CCSK), primitive myxoid mesenchymal tumor of infancy (PMMTI), and central nervous system high-grade neuroepithelial tumor with BCOR ITD in exon 15 (HGNET-BCOR ITDex15). In adults, BCOR ITDs are also reported in endometrial and other sarcomas. The utility of multiplex targeted RNA sequencing for the identification of BCOR ITD in pediatric cancers was investigated. All available archival cases of CCSK, PMMTI, and HGNET-BCOR ITDex15 were collected. Each case underwent anchored multiplex PCR library preparation with a custom-designed panel, with BCOR targeted for both fusions and ITDs. BCOR ITD was detected in all cases across three histologic subtypes using the RNA panel, with no other fusions identified in any of the cases. All BCOR ITDs occurred in the final exon, within 16 codons from the stop sequence. Multiplex targeted RNA sequencing from formalin-fixed, paraffin-embedded tissue is successful at identifying BCOR internal tandem duplications. This analysis supports the use of anchored multiplex PCR targeted RNA next-generation sequencing panels for identification of BCOR ITDs in pediatric tumors. The use of post-analytic algorithms to improve the detection of BCOR ITD using DNA panels was also explored.

OMIC-07. FEASIBILITY AND UTILITY OF EPIGENOMIC PROFILING FOR CHILDHOOD CNS TUMORS IN HONG KONG

Genome-wide DNA methylation profiling has emerged as an important diagnostic tool that complements histopathology for CNS tumors in children and adults. Literature describing its application in Asian countries is nonetheless limited. Herein, we report the feasibility and utility of adopting such platform for children diagnosed with CNS tumors in Hong Kong. A multi-institutional cohort (n=94, 97% of Chinese ethnicity) with CNS embryonal or high grade neuroepithelial tumors (HGNET) diagnosed in Hong Kong from 1996–2020 was assembled based on tissue availability. DNA was extracted from FFPE tumor material (median 301ng, range 13-1000ng), bisulfite converted and profiled with the Infinium Methylation EPIC BeadChip kit. Raw data were analyzed on the German Cancer Research Center MNP 2.0 classifier and through unsupervised dimensionality-reduction analysis (t-SNE) referencing a published CNS tumor reference dataset (GSE90496). The radio-histologic diagnosis included medulloblastoma (n=65), ATRT (n=9), pineal parenchymal tumors (n=7), ETMR (n=5), CNS-PNET (n=4) and other embryonal tumors/HGNETs (n=4). Methylation class could be assigned based on results from MNP 2.0 (calibrated score ≥ 0.9) in 62 patients (66%, including 2 clustering with control) and t-SNE in 22 (23%), while no-match was encountered in 10 (11%). Methylation-based analysis allowed confirmation of diagnosis and assignment of molecular subgroup in 64 patients (68%), confirmation of histologic diagnosis alone in 5 (5%) and resulted in revision/reassignment of diagnosis in 13 (14%). Among medulloblastoma samples that were assigned molecular tumor classes (n=57), 8 clustered with WNT-activated medulloblastoma, 13 with SHH-activated medulloblastoma, 10 with Group 3 medulloblastoma, 21 with Group 4 medulloblastoma, and 5 with non-medulloblastoma entities (high-grade gliomas=3, ETMR=1, ATRT=1). In conclusion, epigenomic profiling allowed refinement of disease classification for pediatric CNS tumors. Availability of such methodology in Asia sets the stage for international collaborations in molecularly-driven trials.

HGG-37. UPFRONT TARGETED THERAPY FOR THE TREATMENT OF BRAFV600E-MUTANT PEDIATRIC HIGH-GRADE GLIOMA – A MULTI-INSTITUTIONAL EXPERIENCE

IntroductionSustained responses to molecular targeted therapy with BRAF with or without MEK inhibitors have been reported in patients with recurrent BRAFV600E-mutant pediatric high-grade gliomas (pHGG). The role of upfront targeted therapy in this population, however, has not yet been established. MethodsWe performed a retrospective, multi-institutional record review of patients with BRAFV600E-mutant pHGGs, treated with off-label BRAF and/or MEK inhibitors as part of their initial adjuvant therapy. ResultsSeventeen patients were identified (median age at diagnosis, 8.8 years, range 1.8–20.2). Histologic diagnoses included HGG/glioblastoma (n=10), anaplastic ganglioglioma (n=3), high-grade neuroepithelial tumor (n=2), diffuse midline glioma (n=1) and anaplastic astroblastoma (n=1). Ten patients underwent biopsy (n=8) or subtotal resection (n=2), while near-total or complete resection was accomplished in seven. Concomitant genetic alterations including CDKN2A/B loss, H3K27M and TERT promotor mutations were found in eight tumors. Thirteen patients received focal radiation therapy (RT) and one received craniospinal irradiation prior to targeted therapy. Adjuvant targeted therapy was initiated shortly after diagnosis or completion of RT. Five patients received BRAF-inhibitor monotherapy (dabrafenib or vemurafenib). Twelve patients received combination therapy with the addition of a MEK inhibitor (trametinib). For patients with measurable disease, best responses per COG criteria were CR (n=3), PR (n=7), SD (n=3) and PD (n=1). With median follow-up of 29 months (range 8–78), two-year PFS and OS for the cohort were 74.7% and 81.1%, respectively. Ten (59%) patients remain free of disease recurrence or progression. Grade 3 or higher toxicities were reported in four patients (neutropenia, skin toxicity/photosensitivity, fatigue and weight loss), leading to therapy discontinuation in two. ConclusionsUpfront targeted therapy for patients with BRAFV600E mutant pHGG appears tolerable and effective, with a durable disease control rate that is superior to historical data. This promising paradigm is currently being evaluated prospectively in the COG ACNS1723 clinical trial.