Intracranial mesenchymal tumors with FET-CREB fusion are composed of at least two epigenetic subgroups distinct from meningioma and extracranial sarcomas

‘Intracranial mesenchymal tumor, FET‐CREB fusion‐positive’ occurs primarily in children and young adults and has previously been termed intracranial angiomatoid fibrous histiocytoma (AFH) or intracranial myxoid mesenchymal tumor (IMMT). Here we performed genome‐wide DNA methylation array profiling of 20 primary intracranial mesenchymal tumors with FET‐CREB fusion to further study their ontology. These tumors resolved into two distinct epigenetic subgroups that were both divergent from all other analyzed intracranial neoplasms and soft tissue sarcomas, including meningioma, clear cell sarcoma of soft tissue (CCS), and AFH of extracranial soft tissue. The first subgroup (Group A, 16 tumors) clustered nearest to but independent of solitary fibrous tumor and AFH of extracranial soft tissue, whereas the second epigenetic subgroup (Group B, 4 tumors) clustered nearest to but independent of CCS and also lacked expression of melanocytic markers (HMB45, Melan A, or MITF) characteristic of CCS. Group A tumors most often occurred in adolescence or early adulthood, arose throughout the neuroaxis, and contained mostly EWSR1‐ATF1 and EWSR1‐CREB1 fusions. Group B tumors arose most often in early childhood, were located along the cerebral convexities or spinal cord, and demonstrated an enrichment for tumors with CREM as the fusion partner (either EWSR1‐CREM or FUS‐CREM). Group A tumors more often demonstrated stellate/spindle cell morphology and hemangioma‐like vasculature, whereas Group B tumors more often demonstrated round cell or epithelioid/rhabdoid morphology without hemangioma‐like vasculature, although robust comparison of these clinical and histologic features requires future study. Patients with Group B tumors had inferior progression‐free survival relative to Group A tumors (median 4.5 vs. 49 months, p = 0.001). Together, these findings confirm that intracranial AFH‐like neoplasms and IMMT represent histologic variants of a single tumor type (‘intracranial mesenchymal tumor, FET‐CREB fusion‐positive’) that is distinct from meningioma and extracranial sarcomas. Additionally, epigenomic evaluation may provide important prognostic subtyping for this unique tumor entity.

CSIG-01. EPIGENETIC REPROGRAMMING DRIVES MALIGNANT PERIPHERAL NERVE SHEATH TUMOR (MPNST) DE-DIFFERENTIATION AND TREATMENT RESISTANCE

Schwann cell derived tumors comprising schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors are the most common malignancies of the peripheral nervous system. While schwannomas and neurofibromas are benign, MPNSTs are malignant, metastasize, and respond poorly to treatment. Neurofibromas and MPNSTs are associated with loss of NF1, a tumor suppressor that inhibits Ras/MEK signaling, and MPNSTs alone are distinguished by loss of the Polycomb Repressive Complex 2 (PRC2), an epigenetic regulator of methylation. To understand the genomic mechanisms of Schwann cell tumorigenesis and treatment resistance, we performed DNA methylation profiling, RNA-sequencing, and whole exome sequencing of primary Schwann cell tumor resection specimens (n=119 total: n=66 schwannoma, n=13 neurofibroma, n=40 MPNSTs). Hierarchical clustering identified three epigenetic Schwann cell tumor groups with transcriptional differences in PRC2 target genes associated with Schwann cell differentiation. Integrating biochemical and genomic approaches in primary human tumor cell lines from NF1 intact peripheral nerve, NF1 mutant neurofibromas, and MPNSTs, we found MPNST and neurofibroma cell lines with CRISPR knockout SUZ12 or EZH1/2 neurofibroma cell lines demonstrated repression of Schwann cell differentiation genes and induction of Ras signaling target genes. Further, MPNST cells deficient in PRC2 and NF1 exhibited increased basal active Ras-GTP levels, and therapeutically, PRC2 deficient MPNST cell lines were more resistant to the MEK inhibitor selumetinib and radiotherapy when compared to NF1-deficient neurofibroma cells. Single cell RNA sequencing analysis suggested distinct mechanisms of selumetinib resistance in PRC2 intact neurofibroma cells compared to PRC2-deficient MPNST cells. Taken together, our data demonstrate the importance of epigenetic dysregulation in malignant Schwann cell transformation and suggest differentiation status underlies a novel mechanism of MEK inhibitor resistance.

Prevalence and clinical impact of atrioventricular conduction disease in patients with idiopathic pulmonary arterial hypertension

Background

Although bradycardia-related sudden death is common in patients with idiopathic pulmonary arterial hypertension (IPAH), the prevalence and prognostic significance of atrioventricular (AV) conduction disease in this patient group is not well-established.

Objectives

– Determine the prevalence of AV conduction disorders in patients with IPAH

– Investigate the relationship between AV block and functional outcomes and mortality.

Method

12-lead electrocardiograms (ECGs) of patients with IPAH were analysed. Patients were categorised according to the presence or absence of AV block. Demographic, pulmonary haemodynamic, cardiac structural characteristics and expression of genes associated with cardiac conduction were compared and functional and mortality outcomes analysed between groups.

Student's t-tests and χ2 tests were used to compare data. Survival was estimated using Kaplan-Meier analyses. Initial exploratory covariates were included in a univariate analysis and those terms with P-value of <0.1 were then used to generate a Cox proportional-hazards multivariate model.

Results

135 IPAH patients (mean age 55±16 years, 28.1% male) were eligible for analysis. Median follow up was 9 years (interquartile range 4–14 years).

AV block was seen in 34.8% of patients with IPAH compared to 10.8% of matched comparators (p<0.001), drawn from patients attending hospital for non-PAH related reasons.

IPAH patients with conduction disease were more likely to be older (59±16 vs 53±17 years, p=0.038). AV block was associated with more severe right ventricular (RV) basal dilatation (5.1±1.0 vs 4.3±0.7cm, p=0.013) and worse RV function (fractional area change 26±9% vs 31±9%, p=0.14). Pulmonary haemodynamics, right atrial size and resting and exertional oxygen saturations were not significantly different. Expression of HCN1, HCN2, SCN1B, SCN5A, CAV1, and KCN2 genes in peripheral blood from a subcohort was similar between those with and without AV block.

Lower 6 minute walk distances (344±153 vs 408±140m, p=0.035) and worse CAMPHOR scores across all 3 domains were seen in those with AV block (figure 1), and mortality was significantly higher (36.2 vs 13.6%, p=0.002) (figure 2). On multivariate analysis the presence of bundle branch block (BBB) was independently associated with a 2.1-fold increased risk of death (95% CI 1.89–4.85, p=0.045).

Conclusions

AV conduction disorders are more prevalent in IPAH than the general population, and are associated with worse prognosis and functional status. Prospective study is required to validate this finding.

In our cohort AV block could not be explained by hypoxia, differences in pulmonary haemodynamics nor, in a small subgroup, by differential expression of specific transmembrane ion channels implicated in cardiac conduction. More detailed investigation into causal mechanisms of AV block in IPAH could establish whether improved prognosis could be achieved by treatment of AV block.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

ATRT-04. CORRELATION OF CLINICOPATHOLOGIC FEATURES AND CUMULATIVE INCIDENCE OF RELAPSE FOR PATIENTS WITH ATYPICAL TERATOID RHABDOID TUMOR ON ACNS0333: A REPORT FROM THE CHILDREN’S ONCOLOGY GROUP

Purpose

Intensive multi-modal regimens have improved survival for patients with atypical teratoid rhabdoid tumor, however relapse rates remain high. A better understanding of clinical and pathologic features associated with tumor relapse is critical to risk-stratifying patients.

Patients and Methods

ACNS0333 treatment consisted of multi-agent chemotherapy, high-dose chemotherapy, and radiation therapy, lasting approximately 6 months. Variables including patient age, sex, tumor location, M-stage, degree of resection, order of therapy, germline status, and molecular subgroup were analyzed. Cumulative incidence (CI) of event free survival due to relapse was evaluated for each variable.

Results

Thirty-three of 65 evaluable patients had tumor relapse. For the entire cohort, the CI of relapse was 21.8% at 6 months, 40.6% at one year and 50.3% at 4 years. For patients with infratentorial tumors, CI of relapse was 26.3%, 34.2% and 37.2%, at 6 months, 1 and 4 years respectfully compared to 15.3%, 49.9%, and 69.7% for those with supratentorial tumors (p 0.051). Patients with SHH subtype had no relapses in the first 6 months and CI of relapse of 37.5% at 4 years, while those with TYR and MYC subgroups had CI of relapse of 33.3% and 26.7% at 6 months and 46.3% and 73.3% at 4 years respectfully (p 0.088). Patients with germline mutations had a cumulative incidence of relapse of 20% at 6 months and 60% at 12 months compared to 22.6% and 37.7% respectfully for those without. No obvious trends were noted based on other analyzed variables.

Conclusions

ACNS0333 was not powered to determine prognostic indicators of relapse, however, this data suggest interesting trends based on tumor location, subtype and germline status. Infratentorial location and SHH subtype maybe associated with lower risk of relapse. Larger data sets must be compiled to further investigate these variables, perform multivariate analyses and inform risk-stratification on future trials.

Survival Benefit for Individuals With Constitutional Mismatch Repair Deficiency Undergoing Surveillance

Constitutional mismatch repair deficiency syndrome (CMMRD) is a lethal cancer predisposition syndrome characterized by early-onset synchronous and metachronous multiorgan tumors. We designed a surveillance protocol for early tumor detection in these individuals.

Advancing biology-based therapeutic approaches for atypical teratoid rhabdoid tumors

Atypical teratoid rhabdoid tumor (ATRT) is a rare, highly malignant central nervous system cancer arising in infants and younger children, historically considered to be homogeneous, monogenic, and incurable. Recent use of intensified therapies has modestly improved survival for ATRT; however, a majority of patients will still succumb to their disease. While ATRTs almost universally exhibit loss of SMARCB1 (BAF47/INI1/SNF5), recent whole genome, transcriptome, and epigenomic analyses of large cohorts reveal previously underappreciated molecular heterogeneity. These discoveries provide novel insights into how SMARCB1 loss drives oncogenesis and confer specific therapeutic vulnerabilities, raising exciting prospects for molecularly stratified treatment for patients with ATRT.

Is ketamine and lamotrigine interactions responsible for the sub-therapeutic effect of ketamine?

Introduction

The immediate antidepressant effect of Ketamine has become a breakthrough in the treatment of depression. Cytochrome CYP3A4 and 2B6 primarily metabolize Ketamine.

Objectives

The present study explores potential pharmacokinetic and pharmacodynamic interactions of Lamotrigine and Ketamine.

Methods

A literature search was conducted using (“ketamine” OR “Lamotrigine” AND Interactions in PubMed, Embase, and PsycINFO. Our literature search resulted in 72 hits and result in qualified five studies.

Results

We found five studies: one RCT study, a RCT, a crossover design, Two case reports, and one murine model study. In the first RCT conducted on 16 healthy normal volunteer subjects. lamotrigine significantly decreased ketamine-induced perceptual abnormalities (P < 0.001), positive (P < 0.001) and negative symptoms (P < 0.05), and learning and memory impairment (P < 0.05) which shows the counter effect of ketamine. Another study revealed Ketamine evoked increases in all the BPRS subscale scores, and all scores were lower after lamotrigine pretreatment. A case report from 2014 reports the failure of ketamine anesthesia in a patient with lamotrigine overdose. Another case report mentions that Lamotrigine reduced the craving in a patient with ketamine use disorder. A murine model study with lamotrigine showed improved PPI (Prepulse inhibition) ketamine-induced disruption. These results suggest that Lamotrigine may exert this effect via a glutamatergic system.

Conclusions

The literature review suggests that Lamotrigine interferes with glutamatergic neurotransmission reducing the effect of Ketamine. It is not clear how this may impact Ketamine’s antidepressant action. Future large scale and well-designed RCTs are required to confirm these findings.

Conflict of interest

No significant relationships.

Does insomnia increase the risk of suicide in patients with major depressive disorders? national inpatient sample analysis

Introduction

Insomnia is strongly associated with Major depressive disorders (MDD). There is strong evidence that it is one of the risk factor for suicide. Studies have shown the relationship of suicidal behavior in MDD patients with insomnia. However, it has not been evaluated in a large inpatient sample.

Objectives

To evaluate suicidality in MDD patients with insomnia compared to those without insomnia.

Methods

From the National Inpatient Sample (NIS 2006-2015) database using ICD-9 code, we obtained patients with the primary diagnosis of MDD and comorbid diagnosis of insomnia disorders (MDD+S). We compared it with MDD patients without insomnia disorders (MDD-S) by performing a 1:2 match for primary diagnosis code in the unweighted dataset. Suicidal ideation/attempt data were compared between the groups by multivariate logistic regression analysis.

Results

After the diagnostic code matching, 139061 patients were included in the MDD+S group and 276496 patients in the MDD- S group. MDD+S patients were older (47 years vs 45 years, p < 0.001) compared to the MDD-S group. Prevalence of Suicidal ideation/attempt was 56.0% in the MDD+S group and 42.0% in the MDD-S group (p < 0.001). After adjusting for age, sex, and race, MDD+S was associated with 1.8 times higher odds of suicidal behavior compared to the MDD-S group. (Odds ratio: 1.79, 95% confidence interval 1.68-1.91, p < 0.001).

Conclusions

Insomnia in MDD patients is significantly associated with the risk of suicide. It is important to be watchful for insomnia in MDD patients.

Disclosure

No significant relationships.

Social media and its effect on mental health: Friend or foe?

Introduction

Recently, several studies have shown both positive and negative impacts of social media on mental health. However, little is known regarding the reasons for the negative impact of social media on mental health.

Objectives

To evaluate the role of social media on mental health.

Methods

We reviewed the documentary ‘The Social Dilemma’ released on Netflix in September 2020, which explored the role of social media in our life. The documentary discussed the behind the scene development of the social media world.

Results

The central message from the documentary is that all the social media applications we use are capable of hijacking the thought process of your brain and are consciously designed by the artificial intelligence technology in a way that one spends more time on them. It collects users’ data such as topics they like, follow, search, subscribe, shop, and several others. Based on this data it feeds you the information according to your taste and next time you log in on the website, you spend more time on it. This causes positive reinforcement, the more time you spend on a particular topic, the more you will be presented which results in addictive behavior.

Conclusions

It is known that social media addiction is prevalent, and it affects brain like drug and alcohol addiction. This documentary provided technological insight into this type of behavior. Though social media has its pros, it has numerous cons despite being used for right intentions. Better regulatory measures are needed to prevent psychological disorders related to social media usage.

Disclosure

No significant relationships.

Human umbilical cord blood infusions in management of autism spectrum disorder: Narrative review

Introduction

According to CDC’s Autism and Developmental Disabilities Monitoring Network surveillance in 2016, autism spectrum disorder (ASD) was prevalent in 1 in 54 children in 11 states of the US.

Objectives

This systematic review provides an overview of Umbilical Cord Blood Infusion (UCB) to decrease symptoms severity in children with (ASD).

Methods

Systematic literature search was conducted using “Autism” OR “Autism spectrum disorder” AND “Autologous Umbilical Cord Blood Infusion (AUCBI)” OR “umbilical cord blood” OR “Allogeneic Cord Blood” in PubMed, Embase, and PsycINFO. Three studies were qualified on AUCBI.

Results

We found 3 studies on UCBI The UCB Infusion phase-I/ open-label trial showed significant improvement in cognitive and behavior scales, especially in the social domain in the first six months, and was more significant in children with higher baseline nonverbal intelligence quotients. Other study/phase II trial failed to show any effects of UCBI on social communication, vocabulary, and other autism symptoms. On subgroup analysis, the improvement in Clinical Global Impression - Improvement (CGI-I) in children without intellectual disability (ID) with the allogenic (not autologous) UCBI was observed. Another randomized, blinded crossover trial failed to show any difference between improvements in CGI baseline severity scores in placebo vs. cord blood infusion groups.

Conclusions

The data provides evidence to support the efficacy and safety of autologous UCBI in symptom severity reductions and improved clinical outcomes without intellectual disability. However, the evidence is inadequate and future large scale clinical are required.

Can We Avoid Axillary Lymph Node Dissection (ALND) in Patients with 1-2 Positive Sentinel/Low Axillary Lymph Nodes (SLN/LAS+) in the Indian Setting?

The ACOSOG Z0011 study, heralded as a "practice changing" trial, suggested that women with T1-2 breast cancer with 1-2 SLN+, undergoing breast conservation therapy, need not be offered further ALND. However, whether these results are applicable to all women in the Indian setting, it remains debatable. A retrospective audit of all cN0 operated from 2013 to 2018 was conducted. We analyzed the percentage of additional LN positive (LN+) in the ALND group and compared it to the ACOZOG Z11 trial. Of the 2350 cN0 with EBC who underwent LAS, 687 (29%) had positive lymph nodes on final histopathology. Five hundred ninety-seven (86.9%) patients had 1-2 LN+, 40 (5.8%) patients had 3 LN+, and 50 (7.3%) had 4 or more nodes positive. Demographic features in the ACOSOG Z11 are different from those in our study, looking at ACOZOG Z11 versus our cohort-median pT 1.7 cm versus 3 cm, 45% micrometastasis versus 99.16% macrometastasis, and 28-30% grade 3 tumors versus 73.7%. In our cohort 31.82% of the 1-2 LN positive had additional LN+ on ALND. Keeping in mind the difference in clinicopathological features between our cohort and that of ACOZOG Z0011 and that 31.82% of women had additional LN+ on ALND, it may not be appropriate to apply the results of the ACOSOG Z0011 trial directly to our general population. Possibly, only a select subset of patients who match the trial population of the ACOSOG Z11 could be offered observation of the axilla and validated nomograms can be used to identify high-risk patients.

Intracranial mesenchymal tumor with FET-CREB fusion-A unifying diagnosis for the spectrum of intracranial myxoid mesenchymal tumors and angiomatoid fibrous histiocytoma-like neoplasms

Intracranial mesenchymal tumors with FET‐CREB fusions are a recently described group of neoplasms in children and young adults characterized by fusion of a FET family gene (usually EWSR1, but rarely FUS) to a CREB family transcription factor (ATF1, CREB1, or CREM), and have been variously termed intracranial angiomatoid fibrous histiocytoma or intracranial myxoid mesenchymal tumor. The clinical outcomes, histologic features, and genomic landscape are not well defined. Here, we studied 20 patients with intracranial mesenchymal tumors proven to harbor FET‐CREB fusion by next‐generation sequencing (NGS). The 16 female and four male patients had a median age of 14 years (range 4–70). Tumors were uniformly extra‐axial or intraventricular and located at the cerebral convexities (n = 7), falx (2), lateral ventricles (4), tentorium (2), cerebellopontine angle (4), and spinal cord (1). NGS demonstrated that eight tumors harbored EWSR1‐ATF1 fusion, seven had EWSR1‐CREB1, four had EWSR1‐CREM, and one had FUS‐CREM. Tumors were uniformly well circumscribed and typically contrast enhancing with solid and cystic growth. Tumors with EWSR1‐CREB1 fusions more often featured stellate/spindle cell morphology, mucin‐rich stroma, and hemangioma‐like vasculature compared to tumors with EWSR1‐ATF1 fusions that most often featured sheets of epithelioid cells with mucin‐poor collagenous stroma. These tumors demonstrated polyphenotypic immunoprofiles with frequent positivity for desmin, EMA, CD99, MUC4, and synaptophysin, but absence of SSTR2A, myogenin, and HMB45 expression. There was a propensity for local recurrence with a median progression‐free survival of 12 months and a median overall survival of greater than 60 months, with three patients succumbing to disease (all with EWSR1‐ATF1 fusions). In combination with prior case series, this study provides further insight into intracranial mesenchymal tumors with FET‐CREB fusion, which represent a distinct group of CNS tumors encompassing both intracranial myxoid mesenchymal tumor and angiomatoid fibrous histiocytoma‐like neoplasms.

Intracranial temporal bone angiomatoid fibrous histiocytoma: illustrative case

BACKGROUND

Angiomatoid fibrous histiocytoma (AFH) is a rare, slowly progressive neoplasm that most commonly occurs in soft tissues. AFH rarely occurs in bone such as the calvaria. The authors present a case of AFH in the petrous temporal bone, which, to their knowledge, is the first case of AFH in this location.

OBSERVATIONS

A 17-year-old girl presented with worsening positional headaches with associated tinnitus and hearing loss. Imaging demonstrated an extraaxial mass extending into the right cerebellopontine angle, with erosion of the petrous temporal bone, with features atypical for a benign process. The patient underwent retrosigmoid craniotomy for tumor resection. Pathology was consistent with a spindle cell tumor, and genetic testing further revealed an EWSR1 gene rearrangement, confirming the diagnosis of AFH. The patient was discharged with no complications. Her symptoms have resolved, and surveillance imaging has shown no evidence of recurrence.

LESSONS

The authors report the first case of AFH in the petrous temporal bone and only the second known case in the calvaria. This case illustrates the importance of the resection of masses with clinical and imaging features atypical of more benign entities such as meningiomas. It is important to keep AFH in the differential diagnosis for atypical masses in the calvaria and skull base.

MBCL-34. EFFICACY OF METHOTREXATE (MTX) ACCORDING TO MOLECULAR SUB-TYPE IN YOUNG CHILDREN WITH MEDULLOBLASTOMA (MB): A REPORT FROM CHILDREN’S ONCOLOGY GROUP PHASE III TRIAL ACNS0334

ACNS0334, a Phase 3 trial, compared outcomes of children <36 months treated with intensive chemotherapy +/-high-dose methotrexate. Nodular-desmoplastic M0-stage MB were excluded. Treatment included 3 induction cycles (cyclophosphamide/etoposide/vincristine/cisplatin+/-mtx) and 3 consolidation cycles (carboplatin/thiotepa with stem cell rescue). Radiation (RT) was at physician discretion. Molecular sub-typing was by DNA-methylation. Log-rank testing was used to compare survival differences. Molecular sub-typing of 38 MB identified 11 Sonic Hedgehog (SHH), 25 Group 3 (GP3), 2 Group 4 (GP4). Five-year survival (OS) was 100% for 5 SHH with MTX and 4 SHH without MTX; 80% for 10 GP3 with MTX, 40% for 15 GP3 without MTX (p=0.025). Only 6/14 survivors received RT: 4 for residual following therapy (1 SHH and 3 GP3) and 2 GP3 salvaged after progression. Two GP3 deaths were associated with toxicity; all others were due to disease. Histology among SHH was nodular-desmoplastic (8) or classic (3); GP3 histology was classic (17) or anaplastic (7). Whole-exome sequencing identified 6 somatic PTCH1 and 1 germline SUFU alteration(s) among 9 SHH. Among GP3, no p53 mutations were found; copy-number analysis identified 5/25 with myc-amplification, 5/25 iso17q, 11/25 with 8 loss, 14/25 with loss of 11. Among GP3, 14/19 had no significant germline mutation. ACNS0334 achieved 100% survival for metastatic SHH. Benefit of methotrexate was observed in GP3 MB supporting incorporation of methotrexate into standard therapy for GP3. Upfront central pathology review and molecular sub-typing are critical for future clinical trial risk stratification of young children with embryonal tumors.

ATRT-30. RETROSPECTIVE ANALYSIS OF CHILDREN WITH ATYPICAL TERATOID RHABDOID TUMOR TREATED ACCORDING TO ACNS0333

Atypical teratoid rhabdoid tumor (ATRT) is a central nervous system tumor with poor outcome. ACNS0333, a Children’s Oncology Group phase 3 trial, enrolled 65 evaluable patients who received two cycles of induction chemotherapy, three cycles of consolidative high-dose chemotherapy (HDCT), and focal radiation therapy (RT) pre- or post-consolidation. Craniospinal irradiation (CSI) was left to clinician discretion. We retrospectively analyzed medical records of 27 children treated at our institutions according to ACNS0333. Median age at diagnosis was 14 months (range 4–165); 13 (48%) were male. M-stage was M0, M2, and M3 for 18 (66%), 5 (19%), and 4 (15%), respectively. Tumor location was supratentorial (n=14, 52%), infratentorial (n=12, 44%), or both (n=1, 4%). Complete resection was achieved for 17 (63%). All but one completed induction. Of 13 (51%) with residual disease at diagnosis, 5 (36%) and 7 (50%), respectively, exhibited complete and partial response to induction. Three patients progressed on therapy, and six progressed after completion of therapy at a median of 9.7 months. In all, 18 patients completed RT (16 focal/4 CSI and 6 pre-/12 post-consolidation). Three died of therapy-related toxicity (two in primary therapy and one in relapse therapy), and 8 died of disease. Sixteen patients (59%) are alive at a median follow up of 53 months (range 9–114). Of 17 with germline testing, eight (47%) had rhabdoid predisposition syndrome of whom three are alive. At the time of presentation, data for approximately 50 patients is expected, and we will compare outcomes to soon-to-be published data from ACNS0333.

ETMR-22. TITLE: DEFINING THE CLINICAL AND PROGNOSTIC LANDSCAPE OF EMBRYONAL TUMORS WITH MULTI-LAYERED ROSETTES (ETMRs), A RARE BRAIN TUMOR REGISTRY (RBTC) STUDY

ETMR, an aggressive disease characterised by C19MC alterations, were previously categorised as various histologic diagnoses. The clinical spectrum and impact of conventional multi-modal therapy on this new WHO diagnostic category remains poorly understood as a majority of ~200 cases reported to date lack molecular confirmation. We undertook comprehensive clinico-pathologic studies of a large molecularly confirmed cohort to improve disease recognition and treatment approaches. Amongst 623 CNS-PNETs patients enrolled in the RBTC registry, 159 primary ETMRs were confirmed based on a combination of FISH (125), methylation analysis (88), SNP and RNAseq (32) analyses; 91% had C19MC amplification/gains/fusions, 9% lacked C19MC alterations but had global methylation features of ETMR NOS. ETMRs arose in young patients (median age 26 months) predominantly as localized disease (M0-72%, M2-3 -18%) at multiple locations including cerebrum (60%) cerebellum (18%), midline structures (6%); notably 10% were brainstem primaries mimicking DIPG. Uni-and multivariate analyses of clinical and treatment details of curative regimens available for 110 patients identified metastatic disease (p=0.002), brainstem locations(p=0.005), extent of surgery, receipt of multi-modal therapy including high dose chemotherapy and radiation (P<0.001) as significant treatment prognosticators, while C19MC status, age and gender were non-significant risk factors. Analyses of events in all patients showed respective EFS at 3 and 12 months of 84%(95%CI:77–91) and 37%(95%CI:20–41) and 4yr OS of 27%(95%CI:18–37) indicating despite intensified therapies ETMR is a rapidly progressive and fatal disease. Our comprehensive data on the largest cohort of molecularly-confirmed ETMRs provides a critical framework to guide current clinical management and development of clinical trials.

SWK-10. TELEHEALTH IN OUTPATIENT PEDIATRIC NEURO-ONCOLOGY CARE

BACKGROUND

Telehealth is an emerging modality that can include patient evaluation, review of test results, and clinical decision-making. Access to care and quality of life are challenges for patients with pediatric brain tumors and their families. Herein we describe the introduction of video visits within our outpatient services led by nurse practitioners and nurse coordinators.

METHODS

The pediatric neuro-oncology program at University of California, San Francisco - Benioff Children’s Hospital (UCSF) established a robust telehealth practice to improve access to care for children and young adults with brain and spine tumors. Our nursing team identifies appropriate time points to offer video visits in lieu of in-person visits. Families are guided to connect through secure video conferencing. Data was collected retrospectively through electronic medical record schedules, billing records, and UCSF patient satisfaction surveys.

RESULTS

Since 2015 we have utilized telehealth for over 400 encounters. The service was limited to patients located in California. Introduction of telehealth resulted in savings of 2300 hours of travel by car, over $22,000 in gas, and over 127,000 miles traveled. Surveys indicate patient satisfaction is equal to or better than in-person experiences. Anecdotally, this service allows for face-to-face contact with patients who have significant barriers to travel. Challenges have included technology platforms, native language, provider and patient acceptance, and billing.

CONCLUSION

Overall, telehealth is feasible as a tool to deliver outpatient care in pediatric neuro-oncology. Implementation of video visits in clinical practice increases access to neuro-oncologic care and improves quality of life for patients and families.

IMMU-18. FAVORABLE OUTCOME IN REPLICATION REPAIR DEFICIENT HYPERMUTANT BRAIN TUMORS TO IMMUNE CHECKPOINT INHIBITION: AN INTERNATIONAL RRD CONSORTIUM REGISTRY STUDY

Pediatric brain tumors with replication repair deficiency (RRD) are hypermutant and may respond to immune checkpoint inhibition (ICI). We performed a consortium registry study of ICI in recurrent RRD cancers. Clinical and companion biomarkers were collected longitudinally on all patients. Biomarkers included tumor mutational burden (TMB), neoantigens and genetic signatures obtained from whole genome and exome sequencing. Immune inference was obtained by RNAseq and T cell rearrangement was collected in the tumor and in blood throughout treatment. Of the 46 tumors on the study, 32 were brain tumors with glioblastoma in 96%. Rapid, objective responses (>50%) were observed in 50% of glioblastomas. Three year overall survival for the whole cohort was 48+/-8% which compares favorably with historical controls. Brain tumors fared worse with OS of 39+/-10% and late recurrences observed even after 2 years of therapy (p=0.02). Tumor size and acute “flare” constitute poor outcome throughout all cancers. While all tumors are hypermutant, TMB and predicted neoantigens correlated with response to ICI (p=0.02). Specific signatures extracted from SNVs and total mutations predicted response to ICI and favorable outcome (p=0.005). RNA inference and TCR reveal that the FLARE phenotype is mostly acute nonspecific immune response and not true progression. Finally, glioblastomas (n=8) which failed single agent ICI had favorable responses to combinational immunotherapies with prolonged survival of 65%+/-8% at one year after failure vs 0 for other patients (p=0.01). RRD glioblastomas exhibit favorable outcome and responses to ICI. Combinational therapies based on tumor and immune signatures of these cancers are necessary.

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.

MBRS-54. POOR SURVIVAL IN REPLICATION REPAIR DEFICIENT HYPERMUTANT MEDULLOBLASTOMA AND CNS EMBRYONAL TUMORS: A REPORT FROM THE INTERNATIONAL RRD CONSORTIUM

BACKGROUND

Mutations in mismatch repair (MMR) and DNA-polymerase (POL) genes lead to DNA replication repair deficiency (RRD), resulting in a growing group of previously under-recognized childhood brain tumors. Medulloblastoma and embryonal tumors are rarely reported in RRD. Their biological and clinical significance is unknown.

METHODS

We analyzed the clinical and genomic data of embryonal tumors registered in the International RRD Consortium.

RESULTS

Twenty-six tumors were centrally reviewed to confirm medulloblastoma (n=18), embryonal-tumor, NOS (n=5), and three glioblastoma (excluded). Embryonal tumors were observed at a young age (median: 7-years, IQR: 5;11), and all but one exhibited clinical cues (café-au-lait macules/ family history) of germline RRD. Medulloblastomas with RRD exhibited high-risk features, including anaplastic histology (50%), and SHH-subgroup with TP53-mutation (50%). Importantly, 68% harbored POLE/POLD1 mutations, resulting in median tumor mutation burden of 164 mut/mb. POL-mutated tumors were significantly ultra-hypermutated (&gt;100 mut/mb) than tumors with MMR-deficiency alone (p=0.015). Synchronous and metachronous tumors were observed in 40%. However 90% of the deaths were related to the diagnosis of embryonal CNS tumor. Median survival for the entire cohort was 17-months (95% CI: 10 to 23). Predicted 3-year survival was 37% for medulloblastoma, with no survivors among other embryonal tumors.

CONCLUSIONS

This is the largest cohort of replication repair deficient medulloblastoma reported till date. The tumors are hypermutated, harbor somatic mutations in TP53 and/or POLE/POLD1, and have very poor survival with current chemo-irradiation based approaches. These biologically unique tumors expand the spectrum of high-risk TP53-mutant SHH-medulloblastoma, and need novel strategies for treatment.