Abstract The blood-brain barrier (BBB) is one of the greatest barriers for the effective treatment of brain tumors, including H3K27-altered diffuse midline glioma (DMG), a near universally fatal childhood brain cancer. The BBB typically requires drugs to be given at maximally tolerated doses that are limited by systemic toxicities, particularly in settings of combination therapy. We have developed a clinically compatible fucoidan nanoparticle (Fi-NP) that homes to P-selectin on tumor vasculature after low-dose radiation (RT) to breach the BBB through an active caveolin-1-dependent mechanism and deliver several classes of targeted therapies. In non-CNS cancer xenograft models and a transgenic mouse model of SHH-driven medulloblastoma with an intact BBB, this approach improved survival while eliminating on-target systemic toxicities. We have now applied this approach to both brainstem and non-brainstem RCAS-TVA mouse models of DMG with an intact BBB. Specifically, we have found that DMG tumor vasculature expresses P-selectin, and that a single low-dose 2 Gy fraction of ionizing radiation further enhances it in a time-dependent manner up to 24 hours post-treatment. Importantly, we have also found that this P-selectin targeted drug delivery approach facilitates DMG tumor localization of Fi-NP encapsulated EZH2 inhibitor tazemetostat (EPZ-6438) as well as larger macromolecules including the PROTAC BET degrader dBET6, two promising targeted therapies for DMG limited by extremely poor BBB-penetration, while sparing drug delivery to non-tumor healthy brain regions. Work to measure PK, biodistribution, survival benefit, and drug target inhibition is ongoing. Our findings will provide the foundation for this P-selectin targeted Fi-NP approach to be evaluated in clinical trials for children with this lethal cancer.

Abstract BACKGROUND Gliomas are a heterogenous and common cancer in children, adolescents and young adults (CAYA, ages 0-39 years). Little is known about the biologic and clinical implications of gliomas in AYA limiting our ability to appropriately manage these patients. METHODS We compiled a population-based cohort of patients with glioma aged 0-39 years diagnosed between 2000-2020, performed molecular characterization of the tumors and collected clinical data including therapy and long-term outcome. RESULTS A total of 1456 patients, including 873 AYA patients were included. A pathogenic molecular alteration was found in 98% of AYA samples available. Strikingly, pediatric-type mutations were found in 31% of AYA glioma of which 37% were BRAF V600E and 23% FGFR alterations. Important differences were observed between gliomas in children versus AYAs. First, hemispheric tumors were enriched in AYAs compared to midline tumors in children, especially for RAS/MAPK alterations. Second, increased incidence of high grade tumors in AYA compared to children were observed for BRAF V600E and FGFR mutations (p<0.0001). In contrast, if these alterations were identified in AYA and the tumor was low grade, outcome was improved for BRAF V600E and FGFR mutant tumors in AYAs compared to pediatrics (for BRAF V600E 5 year PFS 55.6% <10 years, 78.1% for 10-20 years and 87.1% for 10-20 years of age, p=0.0002). Third, a specific time window for transformation was observed for each alteration (BRAF, FGFR, IDH). This correlated with different methylation profiles and transcriptional patterns between early midline and late hemispheric tumors. Increased senescence signatures were observed in older patients with low grade RAS/MAPK driven tumors with superior outcome. CONCLUSIONS Different cell of origin and secondary mutations shape tumor behavior and lead to either transformation or senescence during gliomagenesis in CAYA. These can affect early interventions and tailored approaches for gliomas by age and molecular alteration.

Pineal parenchymal tumors are rare neoplasms for which evidence-based treatment recommendations are lacking. These tumors vary in biology, clinical characteristics, and prognosis, requiring treatment that ranges from surgical resection alone to intensive multimodal antineoplastic therapy. Recently, international collaborative studies have shed light on the genomic landscape of these tumors, leading to refinement in molecular-based disease classification in the 5th edition of the World Health Organization (WHO) classification of tumors of the central nervous system. In this review, we summarize the literature on diagnostic and therapeutic approaches, and suggest pragmatic recommendations for the clinical management of patients presenting with intrinsic pineal region masses including parenchymal tumors (pineocytoma, pineal parenchymal tumor of intermediate differentiation, and pineoblastoma), pineal cyst, and papillary tumors of the pineal region.

Abstract Intrinsic brainstem tumors arising in pediatric, adolescent, and young adult patients comprise a spectrum of entities, predominantly diffuse midline gliomas (DMG) and IDH mutant astrocytomas. Accurate molecular diagnosis is essential for prognostication and optimal therapy. Therapeutic considerations include inclusion (in IDH mutant) or exclusion (in H3K27M) of adjuvant Temozolomide post radiotherapy and use of molecular targeted therapy (IDH inhibitors). Surgical biopsy, however, is associated with increased risk of permanent neurological deficits and may yield insufficient or non-diagnostic tissue. We hypothesized that minimally-invasive “liquid biopsy” of cerebrospinal fluid (CSF) could represent a superior diagnostic modality in this patient population, employing molecular analysis of cell free DNA (cfDNA). We analyzed 44 CSF samples from 38 unique patients for recurrent driver mutations in brainstem gliomas, including H3K27M, IDH1, and IDH2. MSK-IMPACT, a NY state-authorized hybridization capture-based next-generation panel DNA sequencing assay, was used for analysis. Samples without a detectable driver mutation by MSK-IMPACT testing were further subjected to gene targeted testing by droplet digital PCR. In all, 10/44 (22.7%) samples had mutations detected by MSK-IMPACT using standard calling criteria and 13 of the remaining 34 samples (38.2%) had supporting evidence of a mutation based on manual review. Further testing by ddPCR was performed on a subset of cases (based on DNA availability) which confirmed 7 of the previous low-level mutations and uncovered 4 additional mutations. Overall, 27/44 (61.4%) of cases had detectable evidence of a mutation, and of the 23 patients without a known tissue diagnosis, a driver in the CSF was identified for 47.8% of patients (11/23). Minimally-invasive analysis of CSF cfDNA in patients with intrinsic brainstem tumors has a high diagnostic yield and may obviate the need for tissue biopsy in a majority of patients. Testing with high sensitivity assays is valuable to maximize the rate of detection.

Fusions involving CRAF (RAF1) are infrequent oncogenic drivers in pediatric low-grade gliomas, rarely identified in tumors bearing features of pilocytic astrocytoma, and involving a limited number of known fusion partners. We describe recurrent TRAK1::RAF1 fusions, previously unreported in brain tumors, in three pediatric patients with low-grade glial-glioneuronal tumors. We present the associated clinical, histopathologic and molecular features. Patients were all female, aged 8 years, 15 months, and 10 months at diagnosis. All tumors were located in the cerebral hemispheres and predominantly cortical, with leptomeningeal involvement in 2/3 patients. Similar to previously described activating RAF1 fusions, the breakpoints in RAF1 all occurred 5 & PRIME; of the kinase domain, while the breakpoints in the 3 & PRIME; partner preserved the N-terminal kinesin-interacting domain and coiled-coil motifs of TRAK1. Two of the three cases demonstrated methylation profiles (v12.5) compatible with desmoplastic infantile ganglioglioma (DIG)/desmoplastic infantile astrocytoma (DIA) and have remained clinically stable and without disease progression/recurrence after resection. The remaining tumor was non-classifiable; with focal recurrence 14 months after initial resection; the patient remains symptom free and without further recurrence/progression (5 months post re-resection and 19 months from initial diagnosis). Our report expands the landscape of oncogenic RAF1 fusions in pediatric gliomas, which will help to further refine tumor classification and guide management of patients with these alterations.

BACKGROUND: The management of CNS tumors arising among AYA represents an unmet challenge. Treatment may be split between pediatric and adult centers, often with conflicting approaches. Biology also appears to be distinct compared to younger/older age groups but has yet to be fully characterized. Such features would have important implications for prognostication and informing vulnerabilities for targeted therapies.METHODS: To establish the clinical and molecular landscape of these tumors, we analyzed all cases in patients aged 15-39 years old who were treated at MSKCC between 2018-2021. RESULTS: 302 patients with accompanying MSK-IMPACT targeted sequencing, copy number analysis, Archer fusion panel, and clinical data were found. 239/302 cases (79%) were gliomas, with the remaining consisting mainly of neuro-epithelial tumors (n=15; 5%), meningiomas (9; 3%), ependymomas (10; 3%), and embryonal tumors (7; 2%). Among gliomas, 163/239 (68%) had IDH1/2 mutations, which were significantly more enriched for TP53 (121/163; 74%) and ATRX (90/163; 55%) co-mutations compared to IDH-wild type (IDH-WT) (q<0.0001). In comparison, IDH-WT gliomas (n=76) were enriched for alterations in BRAF (16/76 with SNV, 9/76 fusion; q<0.0001), H3F3A (14/76; q<0.0001), PTEN (10/76; q=0.038), and CDKN2A (16/76; q=0.038). Among 113 patients with high-grade gliomas (WHO grade 3/4), those with IDH-WT tumors (n=34) had a poorer prognosis that those with IDH-mutant tumors (n=79) (1 and 5-year OS of 68% and 28% vs. 97% and 76%, respectively) (p<0.0001). Further, a lower frequency of alterations in TERT (26/113; 23%), EGFR (6/113; 5%), and PDGFRA (4/113; 4%) were observed compared to previous studies for adult-only cohorts (~50-70%, 40%, and 10%, respectively). CONCLUSIONS: IDH-mutant gliomas were the most common tumor type seen in this AYA cohort. However, some alterations characteristic of adult high-grade gliomas (TERT, EGFR, PDGFRA) were not as frequently observed. Additional identification of molecular features that predict response to conventional and targeted therapies is underway.

Abstract Background Pineoblastoma is a rare brain tumor usually diagnosed in children. Given its rarity, no pineoblastoma-specific trials have been conducted. Studies have included pineoblastoma accruing for other embryonal tumors over the past 30 years. These included only occasional children with pineoblastoma, making clinical features difficult to interpret and determinants of outcome difficult to ascertain. Patients and Methods Centrally or independently reviewed series with treatment and survival data from North American and Australian cases were pooled. To investigate associations between variables, Fisher’s exact tests, Wilcoxon-Mann-Whitney tests, and Spearman correlations were used. Kaplan-Meier plots, log-rank tests, and Cox proportional hazards models were used in survival analyses. Results We describe a pooled cohort of 178 pineoblastoma cases from Children’s Oncology Group (n = 82) and institutional series (n = 96) over 30 years. Children <3 years of age have significantly worse survival compared to older children, with 5-year progression-free survival (PFS) and overall survival (OS) estimates of 13.5 ± 5.1% and 16.2 ± 5.3%, respectively, compared with 60.8 ± 5.6% and 67.3 ± 5.0% for ≥3 years old (both P < .0001). Multivariable analysis showed male sex was associated with worse PFS in children <3 years of age (hazard ratio [HR] 3.93, 95% CI 1.80-8.55; P = .0006), suggestive of sex-specific risks needing future validation. For children ≥3 years of age, disseminated disease at diagnosis was significantly associated with an inferior 5-year PFS of 39.2 ± 9.7% (HR 2.88, 95% CI 1.52-5.45; P = .0012) and 5-year OS of 49.8 ± 9.1% (HR 2.87, 95% CI 1.49-5.53; P = .0016). Conclusion Given the rarity of this tumor, prospective, collaborative international studies will be vital to improving the long-term survival of these patients.

Biallelic inactivation of NF2 represents the primary or sole oncogenic driver event in the vast majority of schwannomas. We report on a four-year-old female who underwent subtotal resection of a right medullary intraparenchymal schwannoma. RNA sequencing revealed an in-frame fusion between exon 5 of YAP1 and exon 2 of MAML2. YAP1-MAML2 fusions have previously been reported in a variety of tumor types, but not schwannomas. Our report expands the spectrum of oncogenic YAP1 gene fusions an alternative to NF2 inactivation to include sporadic schwannoma, analogous to what has recently been described in NF2-wildtype pediatric meningiomas. Appropriate somatic and germline molecular testing should be undertaken in all young patients with solitary schwannoma and meningioma given the high prevalence of an underlying tumor predisposition syndrome. In such patients, the identification of a somatic non-NF2 driver alteration such as this newly described YAP1 fusion, can help ascertain the diagnosis of a sporadic schwannoma.

PURPOSE: A subset of pediatric, adolescent and young adult (AYA) gliomas are located in the brainstem, eloquent locations, or present with diffuse/leptomeningeal disease, and are associated with high risk and low yield of biopsy. At the same time, accurate molecular diagnosis is necessary to direct optimal therapy. In such cases, analysis of cell free DNA (cfDNA) form cerebral spinal fluid (CSF) may represent a diagnostic alternative to biopsy. METHODS: We investigated the utility of CSF cfDNA sequencing through a stepwise approach, using clinically validated, targeted molecular assays. Testing was performed using a broad hybrid capture next generation sequencing assay (MSK-IMPACT) and subsequent targeted digital droplet PCR in a subset of cases. RESULTS: We analyzed 17 CSF samples from 17 pediatric (n=6) and AYA (n=11) glioma patients with primary or recurrent disease. Thirteen had tumors located within the brainstem, and four had leptomeningeal involvement. Somatic alterations were detected in 12/17 samples (71%). In 3/4 patients with leptomeningeal involvement, cfDNA testing revealed a BRAF fusion consistent with the diagnosis of diffuse leptomeningeal glioneuronal tumor (DLGNT). Among the 13 patients with brainstem involvement, four had somatic H3 K27M mutations, three had IDH mutations, and one had TP53 and ATRX mutations; five patients had no detectable mutations. CONCLUSION: In our analysis, we found that established glioma hotspot mutations were able to be detected within the CSF. We propose that in patients for whom tissue biopsy is high risk, not feasible, or tissue was nondiagnostic, CSF cfDNA sequencing has a substantial diagnostic yield and should be considered as a valuable novel diagnostic tool. Ongoing research is aiming to further increase the sensitivity of cfDNA testing, especially in patients with very low levels of CSF cfDNA.

Pineoblastomas are rare CNS embryonal tumors, accounting for 30% of pineal tumors, and often affecting infants and young children. 1–3 Historically, tumors were grouped with supratentorial primitive neuroectodermal tumors and treated on high-risk brain tumor protocols with intensive multimodality treatments, often including craniospinal irradiation (CSI). 2 Four distinct molecular subgroups of pineoblastoma have recently been identified (PB-miRNA1, PB-miRNA2, PB-MYC/FOXR2, and PB-RB1). 1,3 PB-miRNA1 and PB-miRNA2 affect older children (median 8.5-11.8 years) while PB-RB1 and PB-MYC/FOXR2 affect younger children (median 1.4-2.1 years). Patients <3 years old have a 5-year overall survival (OS) of 24.2% compared with 77.0% in older children. 1,2 We present a diagnostically challenging case of an infant with a suprasellar tumor found to be a pineoblastoma, PB-RB1 subgroup. This case illustrates challenges in treating PB-RB1, which harbor a poor prognosis and limited radiation options due to pa-tients’ young age. We discuss strategies to limit treatment-related toxicities while improving outcomes for young children with PB-RB1. throughput genetic and epigenetic studies identified increased expression in epidermal growth factor receptors (EGFR) in the RB subgroup of pineoblastoma. Endersby demonstrated the erythro-blastic leukemia viral oncogene homolog inhibitor (pan-ERBB inhibitor) Dacomitinib inhibited EGFR signaling in in vitro models of pineoblastoma and had efficacy in orthotopic models of pediatric brain Many EGFR inhibitors have been tested in children. We treated our patient with Gefitinib given the extensive safety data in pediatric patients and efficacy in treating pediatric brain tumors. Newer agents like lapatinib EGFR signaling require further clinical

Commonly used for Parkinson’s disease (PD), deep brain stimulation (DBS) produces marked clinical benefits when optimized. However, assessing the large number of possible stimulation settings (i.e., programming) requires numerous clinic visits. Here, we examine whether functional magnetic resonance imaging (fMRI) can be used to predict optimal stimulation settings for individual patients. We analyze 3 T fMRI data prospectively acquired as part of an observational trial in 67 PD patients using optimal and non-optimal stimulation settings. Clinically optimal stimulation produces a characteristic fMRI brain response pattern marked by preferential engagement of the motor circuit. Then, we build a machine learning model predicting optimal vs. non-optimal settings using the fMRI patterns of 39 PD patients with a priori clinically optimized DBS (88% accuracy). The model predicts optimal stimulation settings in unseen datasets: a priori clinically optimized and stimulation-naïve PD patients. We propose that fMRI brain responses to DBS stimulation in PD patients could represent an objective biomarker of clinical response. Upon further validation with additional studies, these findings may open the door to functional imaging-assisted DBS programming.

Using 3T functional MRI, Elias et al. show that subcallosal cingulate DBS acutely alters activity in brain regions implicated in mood, including dorsal anterior cingulate cortex, in patients with symptoms of depression. The observed changes correlate with both immediate mood fluctuations and long-term antidepressant outcomes. Deep brain stimulation targeting the subcallosal cingulate area, a hub with multiple axonal projections, has shown therapeutic potential for treatment-resistant mood disorders. While subcallosal cingulate deep brain stimulation drives long-term metabolic changes in corticolimbic circuits, the brain areas that are directly modulated by electrical stimulation of this region are not known. We used 3.0 T functional MRI to map the topography of acute brain changes produced by stimulation in an initial cohort of 12 patients with fully implanted deep brain stimulation devices targeting the subcallosal cingulate area. Four additional subcallosal cingulate deep brain stimulation patients were also scanned and employed as a validation cohort. Participants underwent resting state scans (n = 78 acquisitions overall) during (i) inactive deep brain stimulation; (ii) clinically optimal active deep brain stimulation; and (iii) suboptimal active deep brain stimulation. All scans were acquired within a single MRI session, each separated by a 5-min washout period. Analysis of the amplitude of low-frequency fluctuations in each sequence indicated that clinically optimal deep brain stimulation reduced spontaneous brain activity in several areas, including the bilateral dorsal anterior cingulate cortex, the bilateral posterior cingulate cortex, the bilateral precuneus and the left inferior parietal lobule (P-Bonferroni < 0.0001). Stimulation-induced dorsal anterior cingulate cortex signal reduction correlated with immediate within-session mood fluctuations, was greater at optimal versus suboptimal settings and was related to local cingulum bundle engagement. Moreover, linear modelling showed that immediate changes in dorsal anterior cingulate cortex, posterior cingulate cortex and precuneus activity could predict individual long-term antidepressant improvement. A model derived from the primary cohort that incorporated amplitude of low-frequency fluctuations changes in these three areas (along with preoperative symptom severity) explained 55% of the variance in clinical improvement in that cohort. The same model also explained 93% of the variance in the out-of-sample validation cohort. Additionally, all three brain areas exhibited significant changes in functional connectivity between active and inactive deep brain stimulation states (P-Bonferroni < 0.01). These results provide insight into the network-level mechanisms of subcallosal cingulate deep brain stimulation and point towards potential acute biomarkers of clinical response that could help to optimize and personalize this therapy.

Pineoblastoma is a rare pediatric cancer induced by germline mutations in the tumor suppressors RB1 or DICER1 . Presence of leptomeningeal metastases is indicative of poor prognosis. Here we report that inactivation of Rb plus p53 via a WAP-Cre transgene, commonly used to target the mammary gland during pregnancy, induces metastatic pineoblastoma resembling the human disease with 100% penetrance. A stabilizing mutation rather than deletion of p53 accelerates metastatic dissemination. Deletion of Dicer1 plus p53 via WAP-Cre also predisposes to pineoblastoma, albeit with lower penetrance. In silico analysis predicts tricyclic antidepressants such as nortriptyline as potential therapeutics for both pineoblastoma models. Nortriptyline disrupts the lysosome, leading to accumulation of non-functional autophagosome, cathepsin B release and pineoblastoma cell death. Nortriptyline further synergizes with the antineoplastic drug gemcitabine to effectively suppress pineoblastoma in our preclinical models, offering new modality for this lethal childhood malignancy.

Abstract Young children with embryonal brain tumors including medulloblastoma (MB), supratentorial primitive neuro-ectodermal tumor, or pineoblastoma have historically been considered high-risk patients with poor outcomes despite the use of intensive radiation-sparing treatment. In the ACNS0334 phase III trial, 91 consented children <36 months old with the above diagnoses were randomized to intensive induction chemotherapy with or without methotrexate followed by consolidation with stem cell rescue. Here we present the results of a centralized integrated molecular analysis including global methylation profiling (65/91), and whole exome sequencing of tumor (46/91) and germline (35/91) DNA. Unsupervised clustering analyses of methylation profiles using multiple orthogonal methods against a reference dataset of 1200 pediatric brain tumors, revealed known and new molecular entities. For tumors diagnosed as MB on central pathology review, 7.3% (3/41) had a non-MB molecular diagnosis (2 embryonal tumor with multiple rosettes/ETMR, 1 group MYC pineoblastoma), with the remainder as MB Group SHH (11/41), Group3 (25/41), and Group4 (2/41). Among histologic non-MBs, 3/24 (12.5%) were molecular entities not intended for trial inclusion (1 each for ATRT, pleomorphic xanthoastrocytoma, and high-grade glioma). ETMR, historically considered a rare entity, was molecularly identified in a significant proportion (14/65; 21.5%) of samples. Among MB-SHH, we detected deleterious PTCH1 mutations in 6/9 tumors but none among 5 germline samples tested; a germline SUFU frameshift mutation with tumor LOH was also observed in MB-SHH. Correlation of these and other molecular features to the parallel clinical analysis will yield important markers of risk stratification and predictors of treatment response.

Abstract Pineoblastomas (PB) are rare, aggressive pineal gland tumours with poor global OS of 50–70% and only 15–49% OS for patients <4 years, despite intensive treatments. Recently, three independent groups (German Cancer Research Centre, Rare Brain Tumour Consortium/SickKids, St. Jude Children’s Research Hospital) collectively analyzed large tumour cohorts and revealed molecular sub-groups of PB. To harmonize and better characterize clinico-pathologic associations of these sub-groups, we undertook a meta-analysis of molecular and clinical data of the combined cohorts. Unsupervised consensus cluster analyses of global methylation data from 227 unique cases identified five robust molecular sub-groups of pineal region tumours: PB_miRNA_1, PB_miRNA_2, PB_MYC/FOXR2, and PB_RB, mainly comprised of pediatric WHO grade 4 PBs and PNETs; and a fifth group: named PPTID, comprised of mainly pineal parenchymal tumours of intermediate differentiation, a WHO grade 2–3 tumour common in adults. PB_miRNA_1 and PB_miRNA_2 tumours, primarily arising in children (median ages 7.7, 11.4y, respectively), were characterized by alterations of miRNA biogenesis genes DICER1, DROSHA, and DGCR8. PB_MYC/FOXR2 and PB_RB groups, arising in infants/toddlers (median ages 1.4, 2.0y, respectively), were distinguished by recurrent MYC gain/amplification and RB1 loss, respectively. The PPTID group affected mainly adults (median age 33y) and exhibited limited CNAs. Higher rates of metastasis were observed with PB_miRNA_1 (42%), PB_MYC/FOXR2 (38%), and PB_RB (75%) tumours, compared to PB_miRNA_2 (20%) and PPTID (25%). Results from ongoing integrative survival analyses of this large cohort will provide critical data for design of future clinical trials.

Introduction: Embryonal brain tumors (EBTs) are highly aggressive malignancies predominantly affecting children. They include medulloblastoma (MB), atypical rhabdoid/teratoid tumors (ATRT), pineoblastoma (PB), embryonal tumor multiple rosettes (ETMR)/C19MC-altered tumors, and newly recognized embryonal tumors with FOXR2 activation or BCOR alteration.Areas covered: This review will provide a comprehensive overview and updated of the literature on each of these EBTs. The evolution from location- and histopathology-based diagnosis to more specific and robust molecular-based classification schemes, as well as treatment modalities, will be discussed.Expert commentary: The subgrouping of EBTs with multi-omic profiling has had important implications for risk stratification and discovery of targetable driver pathways. However, these innovations are unlikely to significantly improve survival among high-risk patients until robust preclinical studies are conducted, followed by validation in biology-informed clinical trials.

Pineoblastomas (PBs) are rare, aggressive pediatric brain tumors of the pineal gland with modest overall survival despite intensive therapy. We sought to define the clinical and molecular spectra of PB to inform new treatment approaches for this orphan cancer. Tumor, blood, and clinical data from 91 patients with PB or supratentorial primitive neuroectodermal tumor (sPNETs/CNS-PNETs), and 2 pineal parenchymal tumors of intermediate differentiation (PPTIDs) were collected from 29 centres in the Rare Brain Tumor Consortium. We used global DNA methylation profiling to define a core group of PB from 72/93 cases, which were delineated into five molecular sub-groups. Copy number, whole exome and targeted sequencing, and miRNA expression analyses were used to evaluate the clinico-pathologic significance of each sub-group. Tumors designated as group 1 and 2 almost exclusively exhibited deleterious homozygous loss-of-function alterations in miRNA biogenesis genes ( DICER1 , DROSHA , and DGCR8 ) in 62 and 100% of group 1 and 2 tumors, respectively. Recurrent alterations of the oncogenic MYC-miR-17/92-RB1 pathway were observed in the RB and MYC sub-group, respectively, characterized by RB1 loss with gain of miR-17/92 , and recurrent gain or amplification of MYC . PB sub-groups exhibited distinct clinical features: group 1–3 arose in older children (median ages 5.2–14.0 years) and had intermediate to excellent survival (5-year OS of 68.0–100%), while Group RB and MYC PB patients were much younger (median age 1.3–1.4 years) with dismal survival (5-year OS 37.5% and 28.6%, respectively). We identified age < 3 years at diagnosis, metastatic disease, omission of upfront radiation, and chr 16q loss as significant negative prognostic factors across all PBs. Our findings demonstrate that PB exhibits substantial molecular heterogeneity with sub-group-associated clinical phenotypes and survival. In addition to revealing novel biology and therapeutics, molecular sub-grouping of PB can be exploited to reduce treatment intensity for patients with favorable biology tumors.

Abstract 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.

OBJECTIVE:Many centers are hesitant to perform clinically indicated MRI in patients who have undergone deep brain stimulation (DBS). Highly restrictive guidelines prohibit the use of most routine clinical MRI protocols in these patients. The authors' goals were to assess the safety of spine MRI in patients with implanted DBS devices, first through phantom model testing and subsequently through validation in a DBS patient cohort. METHODS:A phantom was used to assess DBS device heating during 1.5-T spine MRI. To establish a safe spine protocol, routinely used clinical sequences deemed unsafe (a rise in temperature > 2°C) were modified to decrease the rise in temperature. This safe phantom-based protocol was then used to prospectively run 67 spine MRI sequences in 9 DBS participants requiring clinical imaging. The primary outcome was acute adverse effects; secondary outcomes included long-term adverse clinical effects, acute findings on brain MRI, and device impedance stability. RESULTS:The increases in temperature were highest when scanning the cervical spine and lowest when scanning the lumbar spine. A temperature rise < 2°C was achieved when 3D sequences were modified to 2D and when the number of slices was decreased by the minimum amount compared to routine spine MRI protocols (but there were still more slices than allowed by vendor guidelines). Following spine MRI, no acute or long-term adverse effects or acute findings on brain MR images were detected. Device impedances remained stable. CONCLUSIONS:Patients with DBS devices may safely undergo spine MRI with a fewer number of slices compared to those used in routine clinical protocols. Safety data acquisition may allow protocols outside vendor guidelines with a maximized number of slices, reducing the need for radiologist supervision.Clinical trial registration no.: NCT03753945 (ClinicalTrials.gov).

Abstract 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.