Germline Elongator mutations in Sonic Hedgehog medulloblastoma.

Cancer genomics has revealed many genes and core molecular processes that contribute to human malignancies, but the genetic and molecular bases of many rare cancers remains unclear. Genetic predisposition accounts for 5 to 10% of cancer diagnoses in children1,2, and genetic events that cooperate with known somatic driver events are poorly understood. Pathogenic germline variants in established cancer predisposition genes have been recently identified in 5% of patients with the malignant brain tumour medulloblastoma3. Here, by analysing all protein-coding genes, we identify and replicate rare germline loss-of-function variants across ELP1 in 14% of paediatric patients with the medulloblastoma subgroup Sonic Hedgehog (MBSHH). ELP1 was the most common medulloblastoma predisposition gene and increased the prevalence of genetic predisposition to 40% among paediatric patients with MBSHH. Parent-offspring and pedigree analyses identified two families with a history of paediatric medulloblastoma. ELP1-associated medulloblastomas were restricted to the molecular SHHα subtype4 and characterized by universal biallelic inactivation of ELP1 owing to somatic loss of chromosome arm 9q. Most ELP1-associated medulloblastomas also exhibited somatic alterations in PTCH1, which suggests that germline ELP1 loss-of-function variants predispose individuals to tumour development in combination with constitutive activation of SHH signalling. ELP1 is the largest subunit of the evolutionarily conserved Elongator complex, which catalyses translational elongation through tRNA modifications at the wobble (U34) position5,6. Tumours from patients with ELP1-associated MBSHH were characterized by a destabilized Elongator complex, loss of Elongator-dependent tRNA modifications, codon-dependent translational reprogramming, and induction of the unfolded protein response, consistent with loss of protein homeostasis due to Elongator deficiency in model systems7-9. Thus, genetic predisposition to proteome instability may be a determinant in the pathogenesis of paediatric brain cancers. These results support investigation of the role of protein homeostasis in other cancer types and potential for therapeutic interference.

Neurofibromatosis type 1 mosaicism in patients with constitutional mismatch repair deficiency.

Differential diagnosis between constitutional mismatch repair deficiency (CMMRD) and neurofibromatosis type 1 (NF1) is crucial as treatment and surveillance differ. We report the case of a girl with a clinical diagnosis of sporadic NF1 who developed a glioblastoma. Immunohistochemistry for MMR proteins identified PMS2 loss in tumour and normal cells and WES showed the tumour had an ultra-hypermutated phenotype, supporting the diagnosis of CMMRD. Germline analyses identified two variants (one pathogenic variant and one classified as variant(s) of unknown significance) in the PMS2 gene and subsequent functional assays on blood lymphocytes confirmed the diagnosis of CMMRD. The large plexiform neurofibroma of the thigh and the freckling were however more compatible with NF1. Indeed, a NF1 PV (variant allele frequencies of 20%, 3% and 9% and in blood, skin and saliva samples, respectively) was identified confirming a mosaicism for NF1. Retrospective analysis of a French cohort identified NF1 mosaicism in blood DNA in 2 out of 22 patients with CMMRD, underlining the existence of early postzygotic PV of NF1 gene in patients with CMMRD whose tumours have been frequently reported to exhibit somatic NF1 mutations. It highlights the potential role of this pathway in the pathogenesis of CMMRD-associated gliomas and argues in favour of testing MEK inhibitors in this context.

Imaging features to distinguish posterior fossa ependymoma subgroups.

OBJECTIVES: Posterior fossa ependymoma group A (EPN_PFA) and group B (EPN_PFB) can be distinguished by their DNA methylation and give rise to different prognoses. We compared the MRI characteristics of EPN_PFA and EPN_PFB at presentation. METHODS: Preoperative imaging of 68 patients with posterior fossa ependymoma from two centers was reviewed by three independent readers, blinded for histomolecular grouping. Location, tumor extension, tumor volume, hydrocephalus, calcifications, tissue component, enhancement or diffusion signal, and histopathological data (cellular density, calcifications, necrosis, mitoses, vascularization, and microvascular proliferation) were compared between the groups. Categorical data were compared between groups using Fisher's exact tests, and quantitative data using Mann-Whitney tests. We performed a Benjamini-Hochberg correction of the p values to account for multiple tests. RESULTS: Fifty-six patients were categorized as EPN_PFA and 12 as EPN_PFB, with median ages of 2 and 20 years, respectively (p = 0.0008). The median EPN_PFA tumoral volume was larger (57 vs 29 cm3, p = 0.003), with more pronounced hydrocephalus (p = 0.002). EPN_PFA showed an exclusive central position within the 4th ventricle in 61% of patients vs 92% for EPN_PFB (p = 0.01). Intratumor calcifications were found in 93% of EPN_PFA vs 40% of EPN_PFB (p = 0.001). Invasion of the posterior fossa foramina was mostly found for EPN_PFA, particularly the foramina of Luschka (p = 0.0008). EPN_PFA showed whole and homogeneous tumor enhancement in 5% vs 75% of EPN_PFB (p = 0.0008). All mainly cystic tumors were EPN_PFB (p = 0.002). The minimal and maximal relative ADC was slightly lower in EPN_PFA (p = 0.02 and p = 0.01, respectively). CONCLUSION: Morphological characteristics from imaging differ between posterior fossa ependymoma subtypes and may help to distinguish them preoperatively. CLINICAL RELEVANCE STATEMENT: This study provides a tool to differentiate between group A and group B ependymomas, which will ultimately allow the therapeutic strategy to be adapted in the early stages of patient management. KEY POINTS: • Posterior fossa ependymoma subtypes often have different imaging characteristics. • Posterior fossa ependymomas group A are commonly median or lateral tissular calcified masses, with incomplete enhancement, affecting young children and responsible for pronounced hydrocephalus and invasion of the posterior fossa foramina. • Posterior fossa ependymomas group B are commonly median non-calcified masses of adolescents and adults, predominantly cystic, and minimally invasive, with total and homogeneous enhancement.

Predictive factors of long-term follow-up attendance in very long-term childhood cancer survivors.

BACKGROUND: Long-term follow-up (LTFU) clinics have been developed but only some childhood cancer survivors (CCS) attend long-term follow-up (LTFU). OBJECTIVE: To identify factors that influence LTFU attendance. METHODS: Five-year CCS treated for a solid tumor or lymphoma in Gustave Roussy before 2000, included in the FCCSS cohort (French Childhood Cancer Survivor Study), aged >18 years and alive at the date of the LTFU Clinic opening (January 2012) were invited to a LTFU visit. Factors associated with attendance at the LTFU clinic between 2012 and 2020 were estimated using logistic regression analyses. Analyses included different types of factors: clinical (tumor characteristics, cancer treatments, late effects), medical (medical expenses were used as a proxy of survivor's health status), social (deprivation index based on census-tract data relating to income, educational level, proportion of blue-collar workers, and unemployed people living in the area of residence), and spatial (distance to the LTFU clinic). RESULTS: Among 2341 CCS contacted (55% males, mean age at study, 45 years; SD ± 10 years; mean age at diagnosis, 6 years; SD ± 5 years), 779 (33%) attended at least one LTFU visit. Initial cancer-related factors associated with LTFU visit attendance were: treatment with both radiotherapy and chemotherapy (odds ratio [OR], 4.02; 95% CI, 2.11-7.70), bone sarcoma (OR, 2.43; 95% CI, 1.56-3.78), central nervous system primitive tumor (OR, 1.65; 95% CI, 1.02-2.67), and autologous hematopoietic cell transplant (OR, 2.07; 95% CI, 1.34-3.20). Late effects (OR, 1.70; 95% CI, 1.31-2.20), highest medical expenses (OR, 1.65; 95% CI, 1.22-2.22), living in the most advantaged area (OR vs. the most deprived area = 1.60; 95% CI, 1.15-2.22), and shorter distance from LTFU care center (<12 miles) also increased attendance. CONCLUSIONS: Patients who are apparently healthy as well as socially disadvantaged and living far away from the center are less likely to attend LTFU care. PLAIN LANGUAGE SUMMARY: Among 2341 adult childhood cancer survivors contacted between 2012 and 2020, 33% attended at least one long-term follow-up visit. Clinical factors related to attendance were multimodal treatment of first cancer (combining chemotherapy and radiotherapy), stem cell transplant, type of diagnosis (bone tumor and central nervous system primitive tumor), late effects (at least one disease among second malignancy, heart disease, or stroke), and highest medical expenses. In addition, the study identified social and spatial inequalities related to attendance, with independent negative effects of distance and social deprivation on attendance, even though the medical costs related to the long-term follow-up examinations are covered by the French social security system.

Surveillance after childhood cancer: are survivors with an increased risk for cardiomyopathy regularly followed-up?

BACKGROUND: We aimed to study adherence to cardiac screening in long-term childhood cancer survivors (CCS) at high risk of cardiomyopathy. METHODS: This study involved 976 5-year CCS at high risk for cardiomyopathy from the French Childhood Cancer Survivor Study. Determinants of adherence to recommended surveillance were studied using multivariable logistic regression models. Association of attendance to a long-term follow-up (LTFU) visit with completion of an echocardiogram was estimated using a Cox regression model. RESULTS: Among participants, 32% had an echocardiogram within the 5 previous years. Males (adjusted RR [aRR] 0.71, 95% CI 0.58-0.86), survivors aged 36-49 (aRR 0.79, 95% CI 0.64-0.98), Neuroblastoma (aRR 0.53, 95% CI 0.30-0.91) and CNS tumour survivors (aRR 0.43, 95% CI 0.21-0.89) were less likely to adhere to recommended surveillance. Attendance to an LTFU visit was associated with completion of an echocardiogram in patients who were not previously adherent to recommendations (HR 8.20, 95% CI 5.64-11.93). CONCLUSIONS: The majority of long-term survivors at high risk of cardiomyopathy did not adhere to the recommended surveillance. Attendance to an LTFU visit greatly enhanced the completion of echocardiograms, but further interventions need to be developed to reach more survivors.

Molecular characterisation defines clinically-actionable heterogeneity within Group 4 medulloblastoma and improves disease risk-stratification.

Group 4 tumours (MBGrp4) represent the majority of non-WNT/non-SHH medulloblastomas. Their clinical course is poorly predicted by current risk-factors. MBGrp4 molecular substructures have been identified (e.g. subgroups/cytogenetics/mutations), however their inter-relationships and potential to improve clinical sub-classification and risk-stratification remain undefined. We comprehensively characterised the paediatric MBGrp4 molecular landscape and determined its utility to improve clinical management. A clinically-annotated discovery cohort (n = 362 MBGrp4) was assembled from UK-CCLG institutions and SIOP-UKCCSG-PNET3, HIT-SIOP-PNET4 and PNET HR + 5 clinical trials. Molecular profiling was undertaken, integrating driver mutations, second-generation non-WNT/non-SHH subgroups (1-8) and whole-chromosome aberrations (WCAs). Survival models were derived for patients ≥ 3 years of age who received contemporary multi-modal therapies (n = 323). We first independently derived and validated a favourable-risk WCA group (WCA-FR) characterised by ≥ 2 features from chromosome 7 gain, 8 loss, and 11 loss. Remaining patients were high-risk (WCA-HR). Subgroups 6 and 7 were enriched for WCA-FR (p < 0·0001) and aneuploidy. Subgroup 8 was defined by predominantly balanced genomes with isolated isochromosome 17q (p < 0·0001). While no mutations were associated with outcome and overall mutational burden was low, WCA-HR harboured recurrent chromatin remodelling mutations (p = 0·007). Integration of methylation and WCA groups improved risk-stratification models and outperformed established prognostication schemes. Our MBGrp4 risk-stratification scheme defines: favourable-risk (non-metastatic disease and (i) subgroup 7 or (ii) WCA-FR (21% of patients, 5-year PFS 97%)), very-high-risk (metastatic disease with WCA-HR (36%, 5-year PFS 49%)) and high-risk (remaining patients; 43%, 5-year PFS 67%). These findings validated in an independent MBGrp4 cohort (n = 668). Importantly, our findings demonstrate that previously established disease-wide risk-features (i.e. LCA histology and MYC(N) amplification) have little prognostic relevance in MBGrp4 disease. Novel validated survival models, integrating clinical features, methylation and WCA groups, improve outcome prediction and re-define risk-status for ~ 80% of MBGrp4. Our MBGrp4 favourable-risk group has MBWNT-like excellent outcomes, thereby doubling the proportion of medulloblastoma patients who could benefit from therapy de-escalation approaches, aimed at reducing treatment induced late-effects while sustaining survival outcomes. Novel approaches are urgently required for the very-high-risk patients.

Pediatric spinal pilocytic astrocytomas form a distinct epigenetic subclass from pilocytic astrocytomas of other locations and diffuse leptomeningeal glioneuronal tumours.

Pediatric spinal low-grade glioma (LGG) and glioneuronal tumours are rare, accounting for less 2.8-5.2% of pediatric LGG. New tumour types frequently found in spinal location such as diffuse leptomeningeal glioneuronal tumours (DLGNT) have been added to the World Health Organization (WHO) classification of tumours of the central nervous system since 2016, but their distinction from others gliomas and particularly from pilocytic astrocytoma (PA) are poorly defined. Most large studies on this subject were published before the era of the molecular diagnosis and did not address the differential diagnosis between PAs and DLGNTs in this peculiar location. Our study retrospectively examined a cohort of 28 children with LGGs and glioneuronal intramedullary tumours using detailed radiological, clinico-pathological and molecular analysis. 25% of spinal PAs were reclassified as DLGNTs. PA and DLGNT are nearly indistinguishable in histopathology or neuroradiology. 83% of spinal DLGNTs presented first without leptomeningeal contrast enhancement. Unsupervised t-distributed stochastic neighbor embedding (t-SNE) analysis of DNA methylation profiles showed that spinal PAs formed a unique methylation cluster distinct from reference midline and posterior fossa PAs, whereas spinal DLGNTs clustered with reference DLGNT cohort. FGFR1 alterations were found in 36% of spinal tumours and were restricted to PAs. Spinal PAs affected significantly younger patients (median age 2 years old) than DLGNTs (median age 8.2 years old). Progression-free survival was similar among the two groups. In this location, histopathology and radiology are of limited interest, but molecular data (methyloma, 1p and FGFR1 status) represent important tools differentiating these two mitogen-activated protein kinase (MAPK) altered tumour types, PA and DLGNT. Thus, these molecular alterations should systematically be explored in this type of tumour in a spinal location.

Clinico-Radio-Histo-Molecular and Neurocognitive Characteristics of Diffuse Gliomas in Adolescent and Young Adults: A Comprehensive Review.

BACKGROUND: Diffuse gliomas are the most frequent neoplasms in adolescent and young adults (AYAs), especially high-grade gliomas, which have the highest mortality rate. Recent histo-molecular advances are in favour of specialized therapeutic management of AYA patients, which we have analysed in this comprehensive review of the literature. SUMMARY: A literature search was conducted to identify all studies concerning diffuse gliomas and AYAs (15-39 years). We assessed epidemiology, clinical and imaging findings, histo-molecular characteristics, neurosurgical and neuro-oncological management, prognosis, and health-related quality of life. KEY MESSAGES: Diffuse gliomas remain the most frequent brain tumours in the AYA population. Symptoms mainly depend on the tumour location, which varies due to histo-molecular profiles. Specific imaging patterns of histo-molecular subtypes of diffuse gliomas are identified; however, no specific pattern related to the age group has been identified. The literature review favours optimizing the extent of surgical resection for diffuse gliomas, whichever the grade, and suggests a dedicated management for these patients. It seems more relevant to consider the treatment according to the histo-molecular profile of the diffuse glioma rather than the age group. Clinical trials will allow AYA patients to benefit from innovative therapies that could improve their outcome. This literature review suggests the need for a close and long-term psychological follow-up for AYA patients with brain tumour during the transitional care, during adulthood, as well as for their family members. Collaborative efforts are needed between paediatric and adult neurosurgical and neuro-oncological teams, to move forward in the therapeutic management of AYA patients harbouring diffuse gliomas.

Neurocognitive and radiological follow-up of children under 5 years of age treated for medulloblastoma according to the HIT-SKK protocol.

BACKGROUND: The HIT-SKK protocol is used for low/standard-risk medulloblastomas in young children with the aim to eliminate cranial irradiation and its neuropsychological (NP) sequelae. This therapy includes IV and intraventricular (ITV) methotrexate (MTX) potentially responsible for leukoencephalopathy (LE) and neurocognitive disorders. This study describes the risk factors and course of LE, and investigates its correlation with neurocognitive impact. METHODS: A retrospective, multicenter study was conducted in 35 children under 5 years old, with a median follow-up of 72 months (range 14 to 130). The main analysis was performed in 30 patients who received cumulative doses of MTX as per-protocol (group 1). Five patients who received higher cumulative doses of MTX were analyzed separately. All follow-up MRIs and NP assessments were centrally reviewed by experts. RESULTS: Twenty patients in group 1 developed LE, grade 2 and 3 abnormalities did not correlate with higher cumulative doses of ITV-MTX (p = 0.698). Considering the most recent NP evaluation, the Full-Scale IQ (FSIQ) and Wechsler indices were in the average to lower average range. The FSIQ was deficient in 6/17 evaluable patients. Cumulative dose of ITV-MTX was almost associated with decreased processing speed competence (p = 0.055) which was the most frequently impaired neurocognitive domain. Neuropsychological assessment scores were not statistically lower in patients with persistent grade 2 LE at the end of follow-up. CONCLUSION: This study described that the use of cumulative dose of MTX (IV and ITV) according to the HIT-SKK protocol resulted in LE that tented to decrease over time, without significant correlation with a decline in neuro-intellectual skills.

The role of irinotecan-bevacizumab as rescue regimen in children with low-grade gliomas: a retrospective nationwide study in 72 patients.

INTRODUCTION: At least half of children with low-grade glioma (LGG) treated with first line chemotherapy experience a relapse/progression and may therefore need a second-line chemotherapy. Irinotecan-bevacizumab has been recommended in this setting in France after encouraging results of pilot studies. We performed a retrospective analysis to define the efficacy, toxicity and predictors for response to the combination on a larger cohort. METHODS: We reviewed the files from children < 19 years of age with progressive or refractory LGG treated between 2009 and 2016 in 7 French centers with this combination. RESULTS: 72 patients (median age 7.8 years [range 1-19]) received a median of 16 courses (range 3-30). The median duration of treatment was 9 months (range 1.4-16.2). 96% of patients experienced at least disease stabilization. The 6-month and 2-year progression-free survivals (PFS) were 91.7% [IC 95% 85.5-98.3] and 38.2% [IC 95% 28.2-51.8] respectively. No progression occurred after treatment in 18 patients with a median follow-up of 35.6 months (range 7.6-75.9 months). Younger patients had a worse PFS (p = 0.005). Prior chemoresistance, NF1 status, duration of treatment, histopathology or radiologic response did not predict response. The most frequent toxicities related to bevacizumab included grades 1-2 proteinuria in 21, epistaxis in 10, fatigue in 12 and hypertension in 8 while gastro-intestinal toxicity was the most frequent side effect related to irinotecan. CONCLUSIONS: Bevacizumab-irinotecan has the potential of disease control clinically and radiographically in children with recurrent LGG whatever their previous characteristics; in many cases however these responses are not sustained, especially in younger children.

Clinical and molecular heterogeneity of pineal parenchymal tumors: a consensus study.

Recent genomic studies have shed light on the biology and inter-tumoral heterogeneity underlying pineal parenchymal tumors, in particular pineoblastomas (PBs) and pineal parenchymal tumors of intermediate differentiation (PPTIDs). Previous reports, however, had modest sample sizes and lacked the power to integrate molecular and clinical findings. The different proposed molecular group structures also highlighted a need to reach consensus on a robust and relevant classification system. We performed a meta-analysis on 221 patients with molecularly characterized PBs and PPTIDs. DNA methylation profiles were analyzed through complementary bioinformatic approaches and molecular subgrouping was harmonized. Demographic, clinical, and genomic features of patients and samples from these pineal tumor groups were annotated. Four clinically and biologically relevant consensus PB groups were defined: PB-miRNA1 (n = 96), PB-miRNA2 (n = 23), PB-MYC/FOXR2 (n = 34), and PB-RB1 (n = 25). A final molecularly distinct group, designated PPTID (n = 43), comprised histological PPTID and PBs. Genomic and transcriptomic profiling allowed the characterization of oncogenic drivers for individual tumor groups, specifically, alterations in the microRNA processing pathway in PB-miRNA1/2, MYC amplification and FOXR2 overexpression in PB-MYC/FOXR2, RB1 alteration in PB-RB1, and KBTBD4 insertion in PPTID. Age at diagnosis, sex predilection, and metastatic status varied significantly among tumor groups. While patients with PB-miRNA2 and PPTID had superior outcome, survival was intermediate for patients with PB-miRNA1, and dismal for those with PB-MYC/FOXR2 or PB-RB1. Reduced-dose CSI was adequate for patients with average-risk, PB-miRNA1/2 disease. We systematically interrogated the clinical and molecular heterogeneity within pineal parenchymal tumors and proposed a consensus nomenclature for disease groups, laying the groundwork for future studies as well as routine use in tumor diagnostic classification and clinical trial stratification.

What does a non-response to induction chemotherapy imply in high-risk medulloblastomas?

PURPOSE: High-risk medulloblastomas (HR-MB) may not respond to induction chemotherapy, with either post-induction stable (SD) or progressive disease (PD). There is no consensus regarding their optimal management. METHODS: A retrospective, multicentre study investigated patients with non-responder HR-MB treated according to the PNET HR + 5 protocol (NCT00936156) between 01/01/2009 and 31/12/2018. After two courses of etoposide and carboplatin (induction), patients with SD or PD were analyzed. Upon clinician's decision, the PNET HR + 5 protocol was either pursued with tandem high-dose chemotherapy (HDCT) and craniospinal irradiation (CSI) (continuation group) or it was modified (switched group). RESULTS: Forty-nine patients were identified. After induction, 37 patients had SD and 12 had PD. The outcomes were better for the SD group: the 5-y PFS and OS were 52% (95% CI 35-67) and 70% (95% CI 51-83), respectively, in the SD group while the 2-y PFS and OS were 17% (95% CI 3-41) and 25% (95% CI 6-50), respectively, in the PD group (p < 0.0001). The PNET HR + 5 strategy was pursued for 3 patients in the PD group, of whom only one survived. In the SD group, it was pursued for 24/37 patients whereas 13 patients received miscellaneous treatments including a 36 Gy CSI in 12 cases. Despite that continuation and switched group were well-balanced for factors impacting the outcomes, the latter were better in the continuation group than in the switched group: the 5-y PFS were 78% (95% CI 54-90) versus 0% (p < 0.001), and the 5-y OS were 78% (95% CI 54-90) versus 56% (95% CI 23-79) (p = 0.0618) respectively. In the SD group, multivariate analysis revealed that MYC amplification, molecular group 3, and a switched strategy were independent prognostic factors for progression. CONCLUSION: Patients with post-induction SD may benefit from HDCT and CSI, whereas patients with early PD will require new therapeutic approaches.

Multimodal management of surgery- and radiation-refractory meningiomas: an analysis of the French national tumor board meeting on meningiomas cohort.

PURPOSE: Meningiomas represent the most frequent tumor of the central nervous system in adults. While most meningiomas are efficiently treated by surgery and radiotherapy/radiosurgery, there is a small portion of radiation- and surgery-refractory tumors for which there is no clear recommendation for optimal management. The French National Tumor Board Meeting on Meningiomas (NTBM) offers a glimpse on the current management of such patients. METHODS: We retrospectively reviewed the charts of patients presented to the multidisciplinary Meeting between 2016 and 2019. We selected patients with a progressive disease after at least two treatments, including surgery and radiotherapy. RESULTS: In this multicentric cohort of 86 cases, patients harbored 17 (19.8%) WHO Grade I, 48 (55.8%) WHO Grade II and 21 (24.4%) WHO Grade III tumors. The median number of treatments received before inclusion was 3 (range: 2 - 11). Following the Board Meeting, 32 patients (37.2%) received chemotherapy, 11 (12.8%) surgery, 17 (19.8%) radiotherapy, 14 (16.3%) watchful observation and 12 (13.9%) palliative care. After a mean follow-up of 13 months post-inclusion, 32 patients (37.2%) had died from their disease. The mean progression free survival was 27 months after radiotherapy, 10 months after surgery, 8.5 months after chemotherapy (Bevacizumab: 9 months - Octreotide/Everolimus: 8 months). CONCLUSIONS: Surgery- and radiation-refractory meningiomas represent a heterogeneous group of tumors with a majority of WHO Grade II cases. If re-irradiation and redo-surgery are not possible, bevacizumab and octreotide-everolimus appear as a valuable option in heavily pre-treated patients considering the current EANO guidelines.

Radiogenomics of diffuse intrinsic pontine gliomas (DIPGs): correlation of histological and biological characteristics with multimodal MRI features.

OBJECTIVES: The diffuse intrinsic pontine gliomas (DIPGs) are now defined by the type of histone H3 mutated at lysine 27. We aimed to correlate the multimodal MRI features of DIPGs, H3K27M mutant, with their histological and molecular characteristics. METHODS: Twenty-seven treatment-naïve children with histopathologically confirmed DIPG H3K27M mutant were prospectively included. MRI performed prior to biopsy included multi-b-value diffusion-weighted imaging, ASL, and dynamic susceptibility contrast (DSC) perfusion imaging. The ADC and cerebral blood flow (CBF) and blood volume (CBV) were measured at the biopsy site. We assessed quantitative histological data, including microvascular density, nuclear density, and H3K27M-positive nuclear density. Gene expression profiling was also assessed in the samples. We compared imaging and histopathological data according to histone subgroup. We correlated MRI quantitative data with histological data and gene expression. RESULTS: H3.1K27M mutated tumors showed higher ADC values (median 3151 µm2/s vs 1741 µm2/s, p = 0.003), and lower perfusion values (DSC-rCBF median 0.71 vs 1.43, p = 0.002, and DSC-rCBV median 1.00 vs 1.71, p = 0.02) than H3.3K27M ones. They had similar microvascular and nuclear density, but lower H3K27M-positive nuclear density (p = 0.007). The DSC-rCBV was positively correlated to the H3K27M-positive nuclear density (rho = 0.74, p = 0.02). ADC values were not correlated with nuclear density nor perfusion values with microvascular density. The expression of gated channel activity-related genes tended to be inversely correlated with ADC values and positively correlated with DSC perfusion. CONCLUSIONS: H3.1K27M mutated tumors have higher ADC and lower perfusion values than H3.3K27M ones, without direct correlation with microvascular or nuclear density. This may be due to tissular edema possibly related to gated channel activity-related gene expression. KEY POINTS: • H3.1K27M mutant DIPG had higher apparent diffusion coefficient (p = 0.003), lower α (p = 0.048), and lower relative cerebral blood volume (p = 0.02) than H3.3K27M mutant DIPG at their biopsy sites. • Biopsy samples obtained within the tumor's enhancing portion showed higher microvascular density (p = 0.03) than samples obtained outside the tumor's enhancing portion, but similar H3K27M-positive nuclear density (p = 0.84). • Relative cerebral blood volume measured at the biopsy site was significantly correlated with H3K27M-positive nuclear density (rho = 0.74, p = 0.02).

Difficulties encountered by physicians and mental health professionals in evaluating and caring for affective and behavioral problems in pediatric brain tumor survivors.

BACKGROUND: Pediatric brain tumor survivors (PBTS) present a high risk for emotional and behavioral disorders. When addressing these difficulties, differences in study designs; variety of and disagreement about diagnoses; and intricate links of emotional, behavioral, and cognitive issues may complicate the interpretation of studies and probably also the work of clinicians. We aimed to survey the difficulties perceived by physicians and mental health professionals in their practice and their interest in developing a new evaluative tool. METHODOLOGY: We surveyed 29 health professionals involved in the follow-up of this population. They completed questionnaires about their clinical practice (difficulties, needs, activities) and indicated diagnosis hypotheses and treatment plans on a clinical case developed for this study. RESULTS: Emotional and behavioral disorders were reported as difficult to assess for 93% of participants. The overlap of symptoms (90%) and the lack of an adapted diagnostic framework (90%) were the main reasons mentioned. Respectively 93%, 90%, and 65% of participants would at least "often" make referrals to psychological (93%), neuropsychological (90%), and psychiatric (65%) assessments and care. Family and group therapy were less common as was drug management. All participants were in favor of creating a tool to help with diagnosis and treatment. When responding to a clinical case, the heterogeneity of participants' responses highlighted their issues in diagnosing and managing these patients. CONCLUSION: This survey exemplifies the difficulties of health professionals related to the evaluation and management of affective and behavioral disorders experienced by PBTS. It underlines the need to help professionals by initiating systematic assessment strategies with this vulnerable population.

Embryonal tumor with multilayered rosettes, C19MC-altered with sarcomatous differentiation: histopathologic and molecular characterization of one case.

Embryonal tumor with multilayered rosettes, constitutes an aggressive and rare pediatric embryonal tumor of the central nervous system characterized by alterations of the C19MC locus at 19q13.12. Embryonal tumors with multilayered rosettes (ETMRs) span a broad histopathological spectrum with primitive neural features and abundant neuropil. Before the molecular definition of this entity, exceptional cases with heterologous differentiation have been evidenced in the literature. Herein, we report the first case of an ETMR featuring a sarcomatous component with proven C19MC alteration in both components by an in situ hybridization analysis. This data supports the hypothesis of a divergent differentiation of tumoral cells in this case.

The histomolecular criteria established for adult anaplastic pilocytic astrocytoma are not applicable to the pediatric population.

Pilocytic astrocytoma (PA) is the most common pediatric glioma, arising from a single driver MAPK pathway alteration. Classified as a grade I tumor according to the 2016 WHO classification, prognosis is excellent with a 10-year survival rate > 95% after surgery. However, rare cases present with anaplastic features, including an unexpected high mitotic/proliferative index, thus posing a diagnostic and therapeutic challenge. Based on small histomolecular series and case reports, such tumors arising at the time of diagnosis or recurrence have been designated by many names including pilocytic astrocytoma with anaplastic features (PAAF). Recent DNA methylation-profiling studies performed mainly on adult cases have revealed that PAAF exhibit a specific methylation signature, thus constituting a distinct methylation class from typical PA [methylation class anaplastic astrocytoma with piloid features-(MC-AAP)]. However, the diagnostic and prognostic significance of MC-AAP remains to be determined in children. We performed an integrative work on the largest pediatric cohort of PAAF, defined according to strict criteria: morphology compatible with the diagnosis of PA, with or without necrosis, ≥ 4 mitoses for 2.3 mm2, and MAPK pathway alteration. We subjected 31 tumors to clinical, imaging, morphological and molecular analyses, including DNA methylation profiling. We identified only one tumor belonging to the MC-AAP (3%), the others exhibiting a methylation profile typical for PA (77%), IDH-wild-type glioblastoma (7%), and diffuse leptomeningeal glioneuronal tumor (3%), while three cases (10%) did not match to a known DNA methylation class. No significant outcome differences were observed between PAAF with necrosis versus no necrosis (p = 0.07), or with 4-6 mitoses versus 7 or more mitoses (p = 0.857). Our findings argue that the diagnostic histomolecular criteria established for anaplasia in adult PA are not of diagnostic or prognostic value in a pediatric setting. Further extensive and comprehensive integrative studies are necessary to accurately define this exceptional entity in children.

Pineoblastoma segregates into molecular sub-groups with distinct clinico-pathologic features: a Rare Brain Tumor Consortium registry study.

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.

New dosing nomogram and population pharmacokinetic model for young and very young children receiving busulfan for hematopoietic stem cell transplantation conditioning.

BACKGROUND: Busulfan (Bu) is the cornerstone of conditioning regimens prior to hematopoietic stem cell transplantation, widely used in both adults and children for the treatment of malignant and nonmalignant diseases. Despite an intravenous formulation, interindividual variability (IIV) remains high and optimal exposure difficult to achieve, especially in neonates and infants. PROCEDURE: To ensure both efficacy and safety, we set up in 2005 an observational study designed for children not fully assessed during the drug registration procedure. From a large cohort of 540 patients, we developed a Bu population pharmacokinetic model based on body weight (BW) and maturation concepts to reduce IIV and optimize exposure. A new dosing nomogram was evaluated to better fit the population pharmacokinetic model. RESULTS: Bu clearance IIV was significantly decreased from 61.3% (covariate-free model) to 28.6% when combining BW and maturation function. Median Bu area under the curve (AUC) was 1179 µmol/L × min compared to 1025 with the EMA dosing nomogram for children <9 kg. The target AUC was reached for each BW strata, significantly increasing the percentages of patients achieving reaching the targeted AUC as compared to FDA schedule. CONCLUSION: This new model made it possible to propose a novel dosing nomogram that better considered children below 16 kg of BW and allowed better initial exposure as compared to existing dosing schedules. This nomogram, which would be easy to use to determine an optimal dosing schedule in daily practice, will need to be validated in clinical routine. Therapeutic drug monitoring remains strongly advisable for small children and those with specific diseases.

Phase II study of temozolomide and topotecan (TOTEM) in children with relapsed or refractory extracranial and central nervous system tumors including medulloblastoma with post hoc Bayesian analysis: A European ITCC study.

AIM: To assess objective response after two cycles of temozolomide and topotecan (TOTEM) in children with refractory or relapsed miscellaneous extracranial solid and central nervous system (CNS) tumors, including medulloblastoma and primitive neuroectodermal tumors (PNET). PROCEDURE: Multicenter, nonrandomized, phase 2 basket trial including children with solid tumors, completed by a one-stage design confirmatory cohort for medulloblastoma, and an exploratory cohort for PNET. Main eligibility criteria were refractory/relapsed measurable disease and no more than two prior treatment lines. Temozolomide was administered orally at 150 mg/m2 /day followed by topotecan at 0.75 mg/m2 /day intravenously for five consecutive days every 28 days. Tumor response was assessed every two cycles according to WHO criteria and reviewed independently. RESULTS: Thirty-two patients were enrolled and treated in the miscellaneous solid tumor and 33 in the CNS strata; 20 patients with medulloblastoma and six with PNET were included in the expansion cohorts. The median age at inclusion was 10.0 years (range, 0.9-20.9). In the basket cohorts, confirmed complete and partial responses were observed in one glioma, four medulloblastoma, and one PNET, leading to the extension. The overall objective response rate (ORR) in medulloblastoma was 28% (95% CI, 12.7-47.2) with 1/29 complete and 7/29 partial responses, those for PNET 10% (95% CI, 0.3-44.5). Post hoc Bayesian analysis estimates that the true ORR in medulloblastoma is probably between 20% and 30% and below 20% in PNET. The most common treatment-related toxicities of the combination therapy were hematologic. CONCLUSIONS: Temozolomide-topotecan results in significant ORR in children with recurrent and refractory medulloblastoma with a favorable toxicity profile.