CNS-PNET Research Articles

ETMR-15. RECLASSIFICATION OF CHILDHOOD CENTRAL NERVOUS SYSTEM PRIMITIVE NEUROECTODERMAL TUMOR: CLINICAL FEATURES AND OUTCOME

Abstract BACKGROUND The “central nervous system primitive neuroectodermal tumor” (CNS-PNET) nosology was removed from the World Health Organization (WHO) classification after DNA methylation profiling and new tumor entities characterized by specific recurrent genetic alterations were described. The aim of this study was to re-evaluate the diagnosis of CNS-PNET and to describe their clinical characteristics. METHODS Patients aged < 18 years with CNS-PNET or unclassified tumor, who were treated at Gustave Roussy between 1999 and 2019 or enrolled in the PNET HR trial were retrospectively identified. The study included all patients with sufficient archival material for diagnosis re-evaluation. RESULTS Sixty-two patients were eligible for the current analysis. The central histopathological review proposed a diagnosis according to the WHO classification in 58 cases. Out of these cases, 34 embryonal tumors were identified: 22 Embryonal Tumors with Multilayered Rosettes (ETMR), 4 CNS neuroblastomas with FOXR2 activation (CNS NB-FOXR2), 4 CNS high-grade neuroepithelial tumors with BCOR alteration (CNS HGNET-BCOR), 4 medulloblastomas. Another 24 tumors were classified as non embryonal tumors: 11 high-grade gliomas, 5 ependymomas, 4 pineoblastomas, 2 teratomas, one desmoplastic small round cell tumor, and one pilocytic astrocytoma. Four tumors without suspected diagnosis after first analysis remain unclassified after DNA methylation profiling. The 5-year event-free survival and overall survival for patients with ETMR were 14% (95% CI, 4.7-39%) and 27% (95% CI, 14-54%) respectively. For patients with CNS HGNET-BCOR and CNS NB-FOXR2 the median time to relapse was respectively 11 months (range, 0.5 to 1.3 year) and 3.1 years (range 1.7 to 4.4 years). CONCLUSIONS This study confirmed that the former nosology of CNS PNET does not correspond to a homogenous class but encompasses a diversity of rare histomolecular entities with specific clinical characteristics and outcomes.

Effect of erythropoietin-stimulating agent use on belzutifan antitumor activity in patients with VHL disease–associated renal cell carcinoma: Post hoc analysis of the LITESPARK-004 study.

3 Background: The ongoing, open-label, phase 2 LITESPARK-004 study (NCT03401788) showed that belzutifan, a HIF-2α inhibitor, exhibited antitumor activity in patients (pts) with VHL disease associated renal cell carcinoma (RCC), pancreatic neuroendocrine tumors (pNETs), and CNS hemangioblastomas. The most common adverse event (AE) of any grade was anemia and pts could have received erythropoietin-stimulating agents (ESA) and/or blood transfusions for management. This exploratory post-hoc analysis described pattern of ESA use and whether use of ESA impacted antitumor activity to belzutifan in pts with VHL disease. Methods: Pts (≥18 years) with germline VHL alterations, ≥1 measurable nonmetastatic RCC tumor, no tumor of >3 cm requiring immediate surgery, and no prior anticancer systemic treatment received oral belzutifan 120 mg once daily until disease progression, unacceptable toxicity, or pt withdrawal. End points included objective response rate (ORR) and duration of response (DOR) in VHL disease–associated RCC and non-RCC neoplasms per RECIST v1.1 by independent central review, and safety. Efficacy and safety outcomes among pts who received and did not receive ESA were evaluated. Data cutoff was April 1, 2022. Results: Of 61 treated pts, 14 (23%) received ESA and 47 (77%) did not. Median (range) time to onset of ESA use was 151 days (59-886) and median dose per pt was 5 injections (range 1-35). Duration of belzutifan exposure for ≥12 months was achieved in 100% of pts who received ESA vs 92% in pts who did not receive ESA. Median (range) relative dose intensity was 97.4 (51.4-100) and 98.8 (26.4-100) for pts who received and did not receive ESA, respectively. ORR for VHL-associated RCC was 71% (10/14, 95% CI, 42-92) for pts who received ESA and 62% (29/47, 46-76) for those who did not. Median DOR was not reached (NR) for pts who received and who did not receive ESA (NR, range 5.5+ to 33.5+ months and NR, range 5.4+ to 35.8+ months). All pts in both groups had a response for ≥12 months. In pts with CNS hemangioblastomas, ORR was 46% (5/11, 17-77) for pts who received ESA and 44% (17/39, 28-60) for those who did not. In pts with pNETs, ORR was 100% (4/4, 40-100) for pts who received ESA and 89% (16/18, 65-99) for those who did not. Median DOR was not reached for both groups in pts with CNS hemangioblastomas and pNETs. Among pts who received and did not receive ESA, 5 (36%) and 6 (13%) pts had at least 1 dose reduction, respectively. All pts reported at least 1 AE but a larger percentage of pts who received ESA had AEs of grade 3 or higher than those who did not receive ESA (57% and 40%). Conclusions: In this exploratory, post-hoc analysis of LITESPARK-004, data suggests that administration of ESA did not adversely impact overall drug exposure or efficacy of belzutifan in pts with VHL disease associated RCC, CNS hemangioblastomas, and pNETs. Clinical trial information: NCT03401788 .

ETMR-15. Central Nervous System Embryonal Tumor with EWSR1 translocation: Evolving changes in histology, sequencing, and epigenetics at relapse in 2 patients and potential treatment implications

Abstract INTRODUCTION: Histologically diagnosed embryonal tumors (ET) of the central nervous system (CNS) in the pediatric population represent a group of aggressive malignancies with historically poor prognoses. Immunohistochemistry (IHC) and cytogenetics refined tumor classification and improved treatment strategies. Modern advancements in molecular methods including methylation profiling provide further delineation of distinct ET subclasses. CASE DESCRIPTION: We present two cases with initial diagnosis of a CNS embryonal tumor with EWSR1 rearrangement. Relapsed tissue in both cases displayed acquisition of INI-1 loss consistent with atypical teratoid/rhabdoid tumor (AT/RT). The first case presented at 14 months of age with vomiting and altered mental status. Imaging revealed right frontal lobe hemorrhagic mass with signs of increased intracranial pressure; pathology returned as a CNS embryonal tumor with EWSR1-PLAGL1 translocation. Patient ultimately experienced multiple relapses with tumor sample each with INI-1 loss. The second case presented at 11 months of age with new onset seizures and was found to have right frontal tumor; pathology returned as CNS embryonal tumor with EWSR1-PLAGL1 translocation. Patient experienced recurrence in original tumor bed and pathology was consistent with malignant recurrence with INI-1 loss. Methylation profiling for diagnostic samples in both patients was consistent with ET not otherwise specified, while methylation profiling of relapsed tissue in both cases was consistent with AT/RT. EWSR1 translocation was persistent from diagnostic to relapsed samples. CONCLUSION/DISCUSSION: These cases illustrate the need for ongoing analysis in patients with CNS primitive neuroectodermal tumors and EWSR1 rearrangements, and the unique role of molecular studies in relapsed tissue. The emergence of treatment resistance in a subpopulation of cells more consistent with AT/RT suggests these patients could benefit from upfront and experimental treatment approaches for AT/RT.

ETMR-09.In vitro modelling of embryonal tumors with multilayered rosettes (ETMR) and other novel brain tumor types.

Over the last decade, molecular characterization has resulted in many tumors previously classified as central nervous system primitive neuroectodermal tumors (CNS-PNETs) now being classified into their own distinct tumor types. These novel types are often characterized by very specific genomic aberrations. For instance, embryonal tumors with multilayered rosettes (ETMR) harbor amplifications of miRNA cluster C19MC or complex DICER1 mutations, while in CNS neuroblastoma with FOXR2 activation structural aberrations result in aberrant FOXR2 expression. Despite the presence of distinct oncodrivers, our understanding of these tumors is still limited. To elucidate tumor biology and to discover tumor specific treatments, we need to uncover how these oncodrivers contribute to tumorigenesis. However, a bottleneck in basic and translational research of these novel tumor types, is the lack of representative preclinical models, especially in vitro. To overcome this hurdle, we aim to mimic tumor development in genetically modified brain organoids. Human brain organoids derived from pluripotent stem cells are generated to represent either the developing forebrain or cerebellum. To mimic oncodriving events, DNA plasmids are introduced via electroporation into the proposed cell-of-origin populations to knockout tumor suppressor genes or overexpress oncogenes. By detecting fluorescent proteins encoded by the plasmids, electroporated cells are followed over time. Based on our preliminary data, for instance, overexpression of C19MC results in ectopic expansion of the electroporated cells. Ongoing histological and molecular characterizations, including (single cell) transcriptomic and epigenomic analyses, will reveal to which extend these organoid models resemble the specific human tumor types. Although further validation is required, these organoid models provide a novel avenue to study especially brain tumor types with distinct oncodriving events for which patient-derived models have not yet been established. They also allow for in-depth analyses of the potential cells of origin and the contribution of different mutations to tumor biology.

ETMR-10. Retrospective molecular re-evaluation of CNS PNETs; a population-based study

Abstract BACKGROUND: The heterogeneous group of tumors, primitive neuro-ectodermal tumors of the central nervous system (CNS-PNETs), is a group of rare childhood embryonal tumors associated with a poor prognosis. In recent years, molecular analyzes have shown that CNS-PNETs consist of high-grade gliomas (HGG), ependymomas, different embryonal entities like atypical teratoid /rhabdoid tumors (AT/RT), CNS neuroblastoma FOXR2 and embryonal tumor with multi-layered rosettes (ETMR). Each of these tumor types is unusual and long-term clinical follow-up data are sparse. METHODS: We retrospectively re-evaluated all children (0-18 years old) diagnosed with a CNS-PNET in Sweden during 1984-2015. In total, 88 supratentorial CNS-PNETs were identified in the Swedish Childhood Cancer Registry and from these formalin-fixed paraffin-embedded tumor material was available for 69 patients. All tumors were reviewed histopathologically by an experienced neuropathologist and were analyzed using genome-wide DNA methylation profiling and classified by the MNP brain tumor classifier. RESULTS: The largest entities, after re-evaluation, were HGG (30%), CNS NB-FOXR2 (12%), AT/RT (10%) and ETMR (8%). Some tumors were difficult to classify and will be further evaluated molecularly. Some examples: Best treatment results were seen for patients with CNS-NB FOXR2 (5-year PFS: 100%) where all patients had received craniospinal radiotherapy (CSI). Patients with ETMR were all very young and survival data show early progression and poor survival (5-year OS 34%). CONCLUSIONS: Although the patient material is relatively small, it is population-based with long follow-up times. Our findings are in line with other studies and shows that CSI is important for cure for CNS-NB FOXR2 and that intensive multi-modal therapies needs to be evaluated in up-front studies for these rare embryonal tumors.

Salvage Radiosurgery for Recurrent Supratentorial Primitive Neuroectodermal Tumors: A Single Institutional Series and Review of the Literature

Introduction: Supratentorial primitive neuroectodermal tumor is a rare, aggressive intrinsic brain tumor with limited treatment options for recurrent disease. SRS as a treatment modality in the recurrent setting was investigated. Methods: A retrospective review of 8 patients treated with SRS for local or distant recurrence of supratentorial PNET from 1999 to 2014 was conducted. Results: Thirty-six tumors were treated in 15 sessions in 8 patients. The median patient age was 22.5 (interquartile range [IQR], 14.75–43.5 years) with a median 21-month period from diagnosis until SRS (IQR, 16–23.75 months). The median prescription isodose volume was 1.85 cm³ (IQR, 1.85–7.02 cm³); median tumor margin dose was 18 Gy (IQR 14–20 Gy); and median isocenters was 2 (range 1–13). No patients experienced adverse radiation effects. All but 1 patient died, and the median overall survival was 32 months (IQR, 26.75–53.5 months) with median overall survival following SRS of 9.5 months (IQR, 5.25–30 months). Univariate analysis failed to demonstrate a statistically significant association between age, number of gamma knife treatments, interval to gamma knife, and margin radiation dose with overall survival. Discussion/Conclusion: This series supports the use of SRS in patients with recurrent supratentorial PNET following multimodal therapy.

Spinal Primitive Neuroectodermal Tumor (PNET) in a 64-year-old Male Treated with Surgery, Radiotherapy, and Chemotherapy: A Case Report

Primitive neuroectodermal tumors (PNETs) are a heterogeneous group of malignant neoplasms found primarily in childhood and early adulthood. In this paper, we described the case of a 64-year-old male with primary spinal PNET, successfully treated with surgery, craniospinal radiotherapy, and concurrent chemotherapy. This is the case of a 64-year-old male who presented with a 2-month history of bilateral lower extremity weakness and numbness associated with urinary and bowel incontinence. Work-up was done, and the spine's plain magnetic resonance imaging (MRI) revealed a heterogeneously enhancing intradural lesion with an extradural component at the right T9/T10 level, causing mild to moderate cord compression. The patient underwent laminectomy and gross total resection of the said tumor. Histology and immunohistochemistry were consistent with a primitive neuroectodermal tumor of the spine. The tumor recurred three months after the surgery, and the patient was then referred for radiation therapy with concurrent chemotherapy. Repeat spinal MRIs with three- to six-month intervals after treatment showed no tumor recurrence as of August 2021. Primary spinal PNETs are rarely found in adults, especially in the elderly. These tumors currently have no recommendations or guidelines regarding their management. Thus, most cases are presently being managed based on studies on children and central nervous system (CNS) PNETs. This paper presented a case of a successfully treated primary spinal PNET in the elderly. The management was primarily based on studies done on that of the pediatric population and CNS PNETs.

Delta-24-RGD, an Oncolytic Adenovirus, Increases Survival and Promotes Proinflammatory Immune Landscape Remodeling in Models of AT/RT and CNS-PNET.

Atypical teratoid/rhabdoid tumors (AT/RT) and central nervous system primitive neuroectodermal tumors (CNS-PNET) are pediatric brain tumors with poor survival and life-long negative side effects. Here, the aim was to characterize the efficacy and safety of the oncolytic adenovirus, Delta-24-RGD, which selectively replicates in and kills tumor cells. Delta-24-RGD determinants for infection and replication were evaluated in patient expression datasets. Viral replication and cytotoxicity were assessed in vitro in a battery of CNS-PNET and AT/RT cell lines. In vivo, efficacy was determined in different orthotopic mouse models, including early and established tumor models, a disseminated AT/RT lesion model, and immunocompetent humanized mouse models (hCD34+-NSG-SGM3). Delta-24-RGD infected and replicated efficiently in all the cell lines tested. In addition, the virus induced dose-dependent cytotoxicity [IC50 value below 1 plaque-forming unit (PFU)/cell] and the release of immunogenic markers. In vivo, a single intratumoral Delta-24-RGD injection (107 or 108 PFU) significantly increased survival and led to long-term survival in AT/RT and PNET models. Delta-24-RGD hindered the dissemination of AT/RTs and increased survival, leading to 70% of long-term survivors. Of relevance, viral administration to established tumor masses (30 days after engraftment) showed therapeutic benefit. In humanized immunocompetent models, Delta-24-RGD significantly extended the survival of mice bearing AT/RTs or PNETs (ranging from 11 to 27 days) and did not display any toxicity associated with inflammation. Immunophenotyping of Delta-24-RGD-treated tumors revealed increased CD8+ T-cell infiltration. Delta-24-RGD is a feasible therapeutic option for AT/RTs and CNS-PNETs. This work constitutes the basis for potential translation to the clinical setting.

PATH-08. THE IMPORTANCE OF RE-DIAGNOSIS OF TUMORS PREVIOUSLY CLASSIFIED AS CENTRAL NERVOUS SYSTEM PRIMITIVE NEUROECTODERMAL TUMORS

BACKGROUNDThe recent molecular analyses have revealed that central nervous system primitive neuroectodermal tumors (CNS PNETs) those having clusters of small round tumor cells are genetically different tumors. However, the concepts of CNS PNET are complicated, and it is difficult to diagnose them appropriately in clinical field. To overcome this difficulty, we reviewed previous studies associated with CNS PNETs, and carried out several approaches, those are relatively easy access to use in clinics, for our 8 samples of embryonal brain tumors diagnosed CNS PNETs in our institution, initially.METHODSWe used in combination with immunohistochemistry (IHC), Sanger sequence, Pyrosequence, polymerase chain reaction (PCR), real time PCR and copy number analysis referring recent reports.RESULTSIn terms of the diagnosis three out of 8 cases were changed based on the results in this study from previous diagnoses.CONCLUSIONIn this review, it seemed that either the histopathological evaluation or molecular analyses would be not enough to make accurate diagnosis of CNS embryonal brain tumors, and it is essential to combine both of them including recent comprehensive analysis methods.

LINC-07. PREVALENCE AND SPECTRUM OF EARLY ENDOCRINE DISORDERS IN SURVIVORS OF PEDIATRIC EMBRYONAL BRAIN TUMORS (PEBT): EXPERIENCE FROM INDIA

BACKGROUNDSurvivors of pediatric brain tumors are at high risk of developing endocrine disorders, potentially impacting growth,development and quality of life.METHODSetrospective audit of 2-year survivors of PEBT(3-18years at diagnosis)viz. medulloblastoma(MB),Central nervous system Primitive neuro-ectodermal tumors(CNS-PNET) and atypical teratoid/rhabdoid tumor(ATRT) treated January 2006-December 2017 at Tata Memorial Centre,Mumbai, with surgery, cranio-spinal irradiation(CSI; 35Gy in high-risk MB,CNS-PNET,ATRT and 23.4Gy in average-risk MB with tumor boost 19.8Gy)and six cycles of adjuvant chemotherapy(cyclophosphamide,cisplatin and vincristine).Patients were followed up by a paediatric endocrinology team specialized in management of PEBT.RESULTSOf 249 PEBT treated during this period,88 are alive in remission >2 years (69-MB, 15-CNS PNET,4-ATRT),median age at diagnosis 6 years. At a median follow-up of 5.6 years (range 3- 12.5years),63 patients(72%) had at least one endocrine disorder,26(29.%)≥2 hormonal deficiencies. The most common endocrine disorders were central hypothyroidism(57%),growth hormone deficiency(40%), central hypogonadism(5%)and central hypoadrenalism (3.5%).The median time to develop hypothyroidism was 2.8 years(range 5months to 8.5 years) from CSI. Growth hormone replacement therapy began after a median period of 4.2 years(range-1.5 to 11.5years) from CSI. Higher dose of CSI was associated with development of endocrine disorder (odds ratio [OR] 2.71; 95% CI, 1.03 to 7.04,p-0.04).CONCLUSIONSThe high incidence of endocrine deficits in survivors of PEBT necessitates early and lifelong monitoring. Early and appropriate management is crucial to achieve full growth potential.

EPID-03. COMPARISON OF SURVIVAL IN ADULT AND PEDIATRIC PATIENTS WITH MEDULLOBLASTOMA: A 2018 SEER BASED ANALYSIS

Medulloblastoma (MB) is the most common high-grade primary brain malignancy in children and accounts for 1% of adult brain tumors. Previous studies have compared survival in pediatric and adult MB from the National Cancer Institute Surveillance Epidemiology and End Results (SEER) database finding no difference. However, diagnostic subgroup analyses are limited. We examined survival in children (age 0–19) and adults (20–79) coded as MB in the 2018 SEER database (2000–2016), using Kaplan Meier analysis, log-rank test and Cox proportional hazard ratios (HR) with 95% confidence intervals (CI).). MB in SEER-18 is defined as ICD-O-3 histology codes 9470–9474 (n=1,728). ICD 9473, supratentorial PNET (sPNET, n=97) is biologically distinct so was analyzed separately. 5-year survival for MB, excluding sPNET, was similar in children (n = 1,091, 75.3%) and adults (n= 488, 79.1%) (HR=0.97, CI: 0.79 – 1.17, p=0.50). Subtype analyses showed no survival difference comparing adults and children with desmoplastic nodular MB (n=222, p=0.09), large cell MB (n=73, p=0.46), or MB NOS (n=1330, p=0.10). In contrast, children with sPNET had improved survival (n=65, 72.3%) compared to adults (n=29, 51.7%) (HR = 2.0, CI: 1.10 – 3.92; p=0.02,). In conclusion, 2018 SEER data for MB continue to show no survival difference between adults and children, suggesting adult patients could appropriately be entered on pediatric MB treatment protocols. Further analyses of the 2018 data are ongoing adjusting for sex, race, and treatment. Comparison of adults and children with MB and sPNET will be re-evaluated using the new 2016 World Health Organization classification.

ETMR-20. IMPACT OF HIGH DOSE CHEMOTHERAPY WITH AND WITHOUT METHOTREXATE (MTX) ON OUTCOME OF PATIENTS WITH EMBRYONAL TUMORS WITH MULTI-LAYERED ROSETTES (ETMRs): A REPORT FROM CHILDREN’S ONCOLOGY GROUP PHASE III TRIAL ACNS0334

Infant embryonal brain tumors comprise a spectrum of histologic and molecular entities including medulloblastoma (MB) and tumors collectively called CNS PNET’s, including supratentorial PNET (sPNET), pineoblastoma and other less common histologic entities. Non-MB embryonal tumors, historically considered high risk disease, were included in ACNS0334, A Children’s Oncology Group prospective phase III trial which compared efficacy of an induction regimen with and without methotrexate combined with high dose chemotherapy and stem cell rescue; no radiation was mandated. Molecular testing performed after ACNS0334 closure identified 14 patients with embryonal tumors with multi-layered rosettes (ETMRs), a new molecular entity previously classified under various diagnostic categories. ETMR patients made up 20% of the molecularly analyzed ACNS0334 cohort and were predominantly females. Tumors were largely non-metastatic (10/14 M0, 1 M1, 3 M2/M3) and originated in the cerebrum (8), cerebellum (3) and pineal gland (3). Gross total tumor resection was achieved in 5/11 patients with M0/M1 disease; 9/14 patients completed full treatment with 5 randomized to MTX induction and 9 to no-MTX. Five of 14 patients progressed on treatment, one had a toxic death. Disease progression was primarily local (88 %). No difference by methotrexate randomization was observed. Four patients are alive without progression 5–10+ years off therapy, none received radiation. No patients received radiation prior to progression. Four were irradiated after progression and died from disease within 3 to 13 months. Our study, a first report on ETMRs prospectively treated on a clinical trial, suggests high dose chemotherapy benefits a portion of ETMR patients.

C19MC amplification and expression of Lin28A and Olig2 in the classification of embryonal tumors of the central nervous system: A 14-year retrospective study from a tertiary care center.

CNS embryonal tumors (CET) other than medulloblastomas (MB) and atypical teratoid/rhabdoid tumors (AT/RTs), previously designated as 'central nervous system primitive neuroectodermal tumors' ('CNS PNETs'), are a heterogenous subset of tumors with poorly defined diagnostic criteria. Other than the subset of embryonal tumor with multilayered rosettes (ETMR) defined by C19MC amplification, most CETs are diagnosed by exclusion of other molecularly defined entities and histological mimics including MB, AT/RTs, and high-grade gliomas, and termed as CET, not otherwise specified (NOS) in the 2016 WHO classification. To reclassify 'CNS PNETs' as per WHO 2016, and estimate the true proportion of CET, NOS in a tertiary healthcare setting, and to evaluate the diagnostic utility of C19MC amplification, Lin28A and Olig2 expression in the subclassification of CETs. Previously diagnosed cases of 'CNS PNETs' (2002-2016) were first evaluated by immunohistochemistry (IHC) for MIC2, RelaA, L1CAM, IDH1R132H, H3K27M, H3G34R, H3G34V, INI1, and BRG1 proteins and by fluorescence in-situ hybridization (FISH) for EWSR1 translocation to exclude histological mimics. The selected CETs (case cohort) and 79 histological mimics (comparison cohort) comprising of MB, AT/RT, pineal parenchymal tumors, Ewing sarcoma, esthesioneuroblastoma, intraocular medulloepithelioma, and H3G34R mutant high-grade glioma were subject to IHC for Olig2 and Lin28A, and FISH for C19MC amplification. Twenty-two cases of 'CNS PNETs' were retrieved, all of which were negative for the first panel of markers and showed retained INI-1/BRG1 expression. Three of them (3/22, 13.6%) showed C19MC amplification (ETMR, C19MC-altered) with ETMR histology, Lin28A positivity, and Olig2 negativity. Among the remaining 19 CETs, one showed medulloepithelioma histology (Medulloepithelioma, NOS) and remaining were non-descript small round cell tumors (CET, NOS), all negative for Lin28A. Olig2 was positive in only 3 CETs (13.6%), all being CET, NOS. All tumors in the comparison cohort were negative for C19MC amplification, Lin28A and Olig2 except for 27% of ATRTs that were Lin28A positive. ETMR, C19MC-altered constitute less than 14% of CETs, with majority remaining uncharacterized as CET, NOS. Lin28A is 100% sensitive for the detection of C19MC amplification; however, its specificity is limited by its expression in ATRTs. Olig2 expression is seen only in a small subset of CET, NOS and is of limited diagnostic utility.

Embryonal tumors with multi-layered rosettes: a disease of dysregulated miRNAs.

ETMRs are highly lethal, pediatric embryonal brain tumors, previously classified as various histologic diagnoses including supratentorial primitive neuroectodermal tumors (sPNET) and CNS PNET. With recognition that these tumors harbor recurrent amplification of a novel oncogenic miRNA cluster on chr19, C19MC, ETMRs were designated as a distinct biological and molecular entity with a spectrum of histologic and clinical manifestations. We reviewed published literature describing clinical presentation, the genetic and epigenetic drivers of oncogenesis, and recent therapeutic strategies adopted to combat these aggressive tumors. As a consequence of C19MC amplification, ETMRs upregulate several oncogenic and pluripotency proteins, including LIN28A, DNMT3B and MYCN, that confer a unique epigenetic signature reminiscent of nascent embryonic stem cells. In this review, we focus on the dysregulation of miRNAs in ETMR, the major pathogenic mechanism identified in this disease. Despite the use of multi-modal therapeutic regimens, ETMR patients have dismal survival. Understanding the unique biology of these tumors has provided new insights towards novel therapeutic targets.

Embryonal tumors of the central nervous system.

This review aims to give an update on histopathological, molecular and clinical features of central nervous system (CNS) 'embryonal' tumors. The taxonomy of previously called 'CNS primitive neuroectodermal tumor' (CNS PNET) has been deeply modified since the discovery of specific molecular profiles for each various sub-entity of these rare, mainly pediatric, tumors. The term 'embryonal tumors' now refers to medulloblastomas, atypical teratoid rhabdoid tumors (AT/RT) and other rare entities, defined by their specific histopathological features together with expression-based or methylation-based profiling; specific gene mutations or fusions characterize some tumor types. In addition, the compilation of large series of molecular data has allowed to dissecting several of these tumor types in molecular subgroups, increasing the number of tumor entities, and leading to an amazingly complex nosology of rare-to-extremely rare malignancies. This rarity precludes from having strong evidence-based therapeutic recommendations, although international efforts are conducted to define the best treatment strategies. Embryonal tumors now correspond to molecularly well defined entities, which deserve further international collaborations to specify their biology and the appropriate burden of treatment, in order to minimize the long-term side-effects of treatment of these overall rare and severe diseases of childhood.

Prolongation of radiotherapy duration is associated with inferior overall survival in patients with pediatric medulloblastoma and central nervous system primitive neuroectodermal tumors.

The importance of radiotherapy (RT) duration in medulloblastoma in the modern era of chemotherapy has not been well elucidated. The aim of this study was to determine the impact of RT treatment duration on overall survival (OS) in pediatric medulloblastoma and cenral nervous system neuroectodermal tumors (PNETs). The National Cancer Database (NCDB) was queried to identify patients with newly diagnosed medulloblastoma and CNS PNETs diagnosed between 2004 and 2014. Patients were excluded if they had extraneural metastasis, did not receive standard craniospinal irradiation dose, had a nonstandard total dose outside of 54 or 55.8 Gy, did not receive adjuvant chemotherapy, or if the RT duration was outside of the expected range of 37 to 80 days. The Kaplan-Meier estimator was used to estimate the association between RT duration (≤45 days or >45 days) and OS. Multivariate Cox regression was used to assess other confounders of OS. Six-hundred twenty-five patients met inclusion criteria, of which 181 were assigned to the "RT long" (>45 days) cohort (29.0%) and 444 (71.0%) to the "RT short" group (≤45 days). The five-year OS for the "RT short" compared with "RT long" cohort was 82.2% versus 70.9%, respectively (log-rank, P < 0.0037). For average risk patients, the five-year OS was 84.6% versus 86.4% for "RT short" and "RT long," respectively (log-rank, P = 0.40). However, for high-risk patients, five-year OS was 77.7% versus 51.0% (log-rank, P < 0.0001) in the "RT short" and "RT long" cohorts. For patients with high-risk medulloblastoma and CNS PNETs, RT duration >45 days was associated with inferior OS.

Survival in adult and pediatric patients with medulloblastoma: A 2018 SEER-based analysis.

e14529 Background: Medulloblastoma (MB) is a malignant neuroectodermal tumor accounting for 30% of pediatric and only 1% of adult brain tumors. In previous studies comparing survival in pediatric and adult MB from the National Cancer Institute Surveillance Epidemiology and End Results (SEER) database no difference has been found. However, diagnostic subgroup analyses have been limited. Methods: We examined survival in children (age 0-19) and adults (20-79) coded as MB in the 2018 SEER database (2000-2016). We used Kaplan Meier analysis, log-rank test and Cox proportional hazard ratios (HR) with 95% confidence intervals (CI). MB in SEER-18 is defined as ICD-O-3 histology codes 9470–9474 (n = 1,728). ICD 9473, supratentorial PNET (sPNET, n = 97) is biologically distinct and therefore it was analyzed separately. Results: We found that 5-year survival for MB, excluding sPNET, was similar in children (n = 1,091, 75.3%) and adults (n = 488, 79.1%) (HR = 0.97, CI: 0.79 – 1.17, p = 0.50). Furthermore, subtype analyses showed no survival difference comparing adults and children with desmoplastic nodular MB (n = 222, p = 0.09), large cell MB (n = 73, p = 0.46), or MB NOS (n = 1330, p = 0.10). Yet, children with sPNET had improved 5-year survival (n = 65, 72.3%) compared to adults (n = 29, 51.7%) (HR = 2.0, CI: 1.10 – 3.92; p = 0.02,). These findings indicate that while survival in patients with MB is similar across age groups, children with sPNET have improved outcomes. Conclusions: In summary, 2018 SEER data for MB continue to show no survival difference between adults and children, suggesting adult patients could appropriately be entered on pediatric MB treatment protocols. Further analyses of the 2018 data are ongoing adjusting for sex, race, and treatment (chemotherapy or radiation). For sPNET, the apparent improved outcomes for children merit further detailed investigation and will be re-evaluated using the new 2016 World Health Organization classification.

PDTM-19. MYC AND FAK/SRC COMBINATION TREATMENT OF FOXR2-HIGH BRAIN TUMORS

Abstract Brain tumors are the leading cause of cancer-related deaths in children. To identify novel therapeutic targets in two types of pediatric brain tumors, medulloblastoma (MB) and central nervous system primitive neuroectodermal tumors (CNS-PNETs), we performed a Sleeping Beauty transposon mutagenesis screen in mice. In doing this, we identified FOXR2 (Forkhead box R2) as a candidate oncogene in MB. FOXR2 is expressed at high levels in a subset of human MB and increased FOXR2 expression drives MB formation in mice. FOXR2 has been implicated as an oncogene in several cancers of neural original, including CNS-PNET, adult and pediatric high-grade glioma, and malignant peripheral nerve sheath tumors. We have also found that FOXR2 is upregulated in non-MYCN amplified high-risk neuroblastoma. Therefore, we propose that FOXR2 represents a strong candidate for targeted therapy across multiple brain tumor entities. We have uncovered a dual role of FOXR2 in stabilization of CMYC protein and activation of the FAK/SRC signaling pathway. We are working to further define the mechanism of FOXR2-mediated MYC stabilization and FAK/SRC activation. We plan to treat FOXR2-high tumors with combinations of drugs effective against tumors with high MYC, FAK, or SRC in clinical development. Inhibitors or combinations of that score well in vitro will be used to treat mice with orthotopically injected FOXR2-high tumor cells (MB, neuroblastoma, and glioma). In addition, we are working to construct mouse models of FOXR2-driven neural tumors for use in drug testing. We hypothesize that FOXR2-high tumors will be sensitive to MYC and FAK/SRC inhibitor combination therapy, establishing FOXR2 as a molecular marker for treatment success of MYC and FAK/SRC inhibitors in patients.

PATH-06. A TARGETED NGS-BASED OVERALL SOLUTION TO SUPPORT DIAGNOSTICS AND THERAPY PREDICTION IN NEUROONCOLOGY: CONSIDERATIONS FOR A FLEXIBLE AND COST-EFFICIENT PLATFORM CHOICE AND PANEL DESIGN

Abstract Continuous updates add novel molecular markers to the WHO classification of CNS tumors. Additionally, molecularly informed trials may provide the basis for the introduction of additional predictive biomarkers. All these developments will prospectively require molecular testing to a yet unknown extent and still pose challenges to many neuropathology labs. Some of the relevant alterations (e.g. C11orf95-RELA) are hard to assess or complex subclassifications (e.g. for medulloblastomas) are required. Some labs rely on a two-tiered approach: i) methylation arrays for tumor classification and ii) targeted NGS panel sequencing for identifying actionable mutations. However, high initial investment and annual costs for running two platforms in parallel hinder a fast expansion of the new techniques in the breadth of neuropathology. We decided to focus on the sole use of the relatively cost-efficient Mini-Seq NGS platform (Illumina). First, we designed a DNA panel (FFPE, HaloPlex, Agilent; no Covaris required) that is suited for detection of DNA mutations, copy number alterations and chromosomal alterations (459 kbp, 58 genes, 4082 SNPs, 98.83% coverage). We successfully used this platform to support tumor classification in astrocytomas, oligodendrogliomas, meningiomas and medulloblastomas and identified actionable targets of clinical use. We then designed a RNA panel (FFPE, Sure Select, Agilent) that detects gene fusions and covers a broad range of alterations particularly relevant to pediatric tumors (e.g. pediatric glioblastomas, ependymomas, CNS PNETs) (148 kbp, coding sequence of 31 genes, 99.88% coverage). With these two panels we cover the most relevant molecular alterations in the field of neurooncology. The cost-efficient and flexible single platform approach enables state-of-the-art molecular diagnostics in virtually every neuropathology lab in a quality-controlled manner. Functionality is guaranteed for future revisions of the WHO classification as novel biomarkers can be easily included in an adapted panel design.

Prolongation of Radiotherapy Duration is Associated with Inferior Overall Survival in Patients with High Risk Pediatric Medulloblastoma and CNS PNETs

Prolongation of Radiotherapy Duration is Associated with Inferior Overall Survival in Patients with High Risk Pediatric Medulloblastoma and CNS PNETs