Eric Bouffet

Medulloblastoma Comprises Four Distinct Molecular Variants

PURPOSE Recent genomic approaches have suggested the existence of multiple distinct subtypes of medulloblastoma. We studied a large cohort of medulloblastomas to determine how many subgroups of the disease exist, how they differ, and the extent of overlap between subgroups. METHODS We determined gene expression profiles and DNA copy number aberrations for 103 primary medulloblastomas. Bioinformatic tools were used for class discovery of medulloblastoma subgroups based on the most informative genes in the data set. Immunohistochemistry for subgroup-specific signature genes was used to determine subgroup affiliation for 294 nonoverlapping medulloblastomas on two independent tissue microarrays. RESULTS Multiple unsupervised analyses of transcriptional profiles identified the following four distinct, nonoverlapping molecular variants: WNT, SHH, group C, and group D. Supervised analysis of these four subgroups revealed significant subgroup-specific demographics, histology, metastatic status, and DNA copy number aberrations. Immunohistochemistry for DKK1 (WNT), SFRP1 (SHH), NPR3 (group C), and KCNA1 (group D) could reliably and uniquely classify formalin-fixed medulloblastomas in approximately 98% of patients. Group C patients (NPR3-positive tumors) exhibited a significantly diminished progression-free and overall survival irrespective of their metastatic status. CONCLUSION Our integrative genomics approach to a large cohort of medulloblastomas has identified four disparate subgroups with distinct demographics, clinical presentation, transcriptional profiles, genetic abnormalities, and clinical outcome. Medulloblastomas can be reliably assigned to subgroups through immunohistochemistry, thereby making medulloblastoma subclassification widely available. Future research on medulloblastoma and the development of clinical trials should take into consideration these four distinct types of medulloblastoma.

Central nervous system atypical teratoid rhabdoid tumours: The Canadian Paediatric Brain Tumour Consortium experience

BACKGROUND Atypical teratoid rhabdoid tumours (ATRT) are aggressive brain tumours mostly occurring in early childhood. Largest published series arise from registries and institutional experiences (1-4). The aim of this report is to provide population-based data to further characterise this rare entity and to delineate prognostic factors. PATIENTS AND METHODS A national retrospective study of children ⩽18years diagnosed with a central nervous system (CNS) ATRT between 1995 and 2007 was undertaken. All cases underwent central pathology review. RESULTS There were 50 patients (31 males; median age at diagnosis of 16.7months). Twelve patients were >36months. Infratentorial location accounted for 52% of all cases. Nineteen patients (38%) had metastatic disease. Fifteen (30%) underwent gross total resection (GTR). Ten patients (20%) underwent palliation. Among the 40 remaining patients, 22 received conventional chemotherapy and 18 received high dose chemotherapy regimens (HDC); nine received intrathecal chemotherapy and 15 received adjuvant radiation. Thirty of the 40 treated patients relapsed/progressed at a median time of 5.5months (0-32). The median survival time of the entire cohort was 13.5months (1-117.5months). Age, tumour location and metastatic status were not prognostic. Patients with GTR had a better survival (2years overall survival (OS): 60%±12.6 versus 21.7%±8.5, p=0.03). HDC conferred better outcome (2years OS 47.9%±12.1 versus 27.3%±9.5, p=0.036). Upfront radiation did not provide survival benefit. Six of the 12 survivors (50%) did not receive radiation. CONCLUSION The outcome of CNS ATRT remains poor. However, the use of HDC provides encouraging results. GTR is a significant prognostic factor. The role of adjuvant radiation remains unclear.

Conventional MRI cannot predict survival in childhood diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) of childhood has a dismal prognosis. Clinical trials of new agents are vital and it is essential that the correct endpoints and disease assessments are chosen. A retrospective review of magnetic resonance imaging (MRI) scanning in a pure population of DIPG was undertaken. Baseline diagnostic MRI findings included; local tumour extension in upper medulla (74%) or midbrain (62%), metastatic disease (3%), basilar artery encasement (82%), necrosis (33%), intratumoural haemorrhage (26%), hydrocephalus (23%) and dorsal exophytic component (18%). Post-treatment MRI scans demonstrated increases in; leptomeningeal metastatic disease (16%), cystic change/necrosis (48%), enhancement (72%) and intratumoural haemorrhage (32%). Response rates were calculated according to both RECIST (4%) and WHO (24%) criteria. No MRI parameter in either the diagnostic or response scans had prognostic significance. We recommend that currently primary endpoints for DIPG clinical trials should be overall or possibly progression free survival and that new advanced functional imaging techniques should be explored as possible surrogate markers for novel therapy activity rather than conventional MRI response criteria.

Medulloblastoma subgroups remain stable across primary and metastatic compartments

Medulloblastoma comprises four distinct molecular variants with distinct genetics, transcriptomes, and outcomes. Subgroup affiliation has been previously shown to remain stable at the time of recurrence, which likely reflects their distinct cells of origin. However, a therapeutically relevant question that remains unanswered is subgroup stability in the metastatic compartment. We assembled a cohort of 12-paired primary-metastatic tumors collected in the MAGIC consortium, and established their molecular subgroup affiliation by performing integrative gene expression and DNA methylation analysis. Frozen tissues were collected and profiled using Affymetrix gene expression arrays and Illumina methylation arrays. Class prediction and hierarchical clustering were performed using existing published datasets. Our molecular analysis, using consensus integrative genomic data, establishes the unequivocal maintenance of molecular subgroup affiliation in metastatic medulloblastoma. We further validated these findings by interrogating a non-overlapping cohort of 19 pairs of primary-metastatic tumors from the Burdenko Neurosurgical Institute using an orthogonal technique of immunohistochemical staining. This investigation represents the largest reported primary-metastatic paired cohort profiled to date and provides a unique opportunity to evaluate subgroup-specific molecular aberrations within the metastatic compartment. Our findings further support the hypothesis that medulloblastoma subgroups arise from distinct cells of origin, which are carried forward from ontogeny to oncology.

Pituitary stalk thickening and primary central nervous system lymphoma.

We report a 14-year-old girl in whom a diagnosis of primary central nervous system lymphoma was confirmed while receiving growth hormone (GH) for GH deficiency, detected after presenting with short stature. MRI revealed an enhancing and thickened pituitary stalk with absence of the normal bright signal in the posterior pituitary. Regular MRI surveillance detected progression of the neurohypophyseal changes 13 months into GH treatment. Biopsy confirmed this to be B-cell large cell lymphoma. This case highlights the diagnostic and management challenges inherent in treating such children.

Pathological laughter and behavioural change in childhood pontine glioma

SummaryChildren with pontine glioma usually present classically with ataxia, motor deficits and cranial nerve palsies. The pons has generally not been regarded as a structure that mediates complex affective behaviour. However, we report nine children who either at the time of presentation or progression demonstrated marked behavioural changes manifesting as either ȁ8pathological laughterȁ9 or separation anxiety in the form of school refusal. A mechanism of how pontine lesions can cause such complex affective and cognitive behaviour has been suggested to consist of the disruption of a network of cerebro-ponto-cerebellar pathways and the evidence for this mechanism is discussed.

Challenges in management of patients with intracranial germ cell tumor and diabetes insipidus treated with cisplatin and/or ifosfamide based chemotherapy

Patients with intracranial germ cell tumor (IGCT) often present with pituitary dysfunction, including diabetes insipidus (DI). Recent protocols have used pre-radiation chemotherapy with combinations of etoposide, carboplatin and/or cisplatin, and ifosfamide. Management of DI in these patients requires monitoring of electrolytes and fluids during chemotherapy and hyperhydration. All consecutive patients treated with chemotherapy for an IGCT during the period 1990–2007 at the Hospital for Sick Children, Toronto were reviewed. Out of 32 patients who received chemotherapy, 21 had DI. Only cycles containing cisplatin and/or ifosfamide and hyperhydration were considered. DI and non-DI patients were compared for each cycle of chemotherapy. Patients were studied for number of days in hospital per chemotherapy course, daily fluid input and output, changes in dose, schedule and route of administration of desmopressin (DDAVP) during chemotherapy, daily variations in sodium level, electrolyte monitoring requirements per day, and complications related to fluid and electrolyte disturbances. Fifty-four cycles of chemotherapy in DI patients were compared to 25 cycles in non DI patients. All 21 patients with DI required daily change in dosage and schedule of DDAVP. Marked variations in daily sodium level were observed in the DI group. Seventeen courses required prolonged admission in the DI group (one in non DI patients) and 6 patients experienced serious complications. In conclusion, DI is a risk factor for complications when cisplatin and/or ifosfamide based protocols are used. The role of these agents in the management of ICGT should be carefully evaluated and guidelines for management of DI established.

Therapeutic targeting of ependymoma as informed by oncogenic enhancer profiling

Genomic sequencing has driven precision-based oncology therapy; however, the genetic drivers of many malignancies remain unknown or non-targetable, so alternative approaches to the identification of therapeutic leads are necessary. Ependymomas are chemotherapy-resistant brain tumours, which, despite genomic sequencing, lack effective molecular targets. Intracranial ependymomas are segregated on the basis of anatomical location (supratentorial region or posterior fossa) and further divided into distinct molecular subgroups that reflect differences in the age of onset, gender predominance and response to therapy. The most common and aggressive subgroup, posterior fossa ependymoma group A (PF-EPN-A), occurs in young children and appears to lack recurrent somatic mutations. Conversely, posterior fossa ependymoma group B (PF-EPN-B) tumours display frequent large-scale copy number gains and losses but have favourable clinical outcomes. More than 70% of supratentorial ependymomas are defined by highly recurrent gene fusions in the NF-κB subunit gene RELA (ST-EPN-RELA), and a smaller number involve fusion of the gene encoding the transcriptional activator YAP1 (ST-EPN-YAP1). Subependymomas, a distinct histologic variant, can also be found within the supratetorial and posterior fossa compartments, and account for the majority of tumours in the molecular subgroups ST-EPN-SE and PF-EPN-SE. Here we describe mapping of active chromatin landscapes in 42 primary ependymomas in two non-overlapping primary ependymoma cohorts, with the goal of identifying essential super-enhancer-associated genes on which tumour cells depend. Enhancer regions revealed putative oncogenes, molecular targets and pathways; inhibition of these targets with small molecule inhibitors or short hairpin RNA diminished the proliferation of patient-derived neurospheres and increased survival in mouse models of ependymomas. Through profiling of transcriptional enhancers, our study provides a framework for target and drug discovery in other cancers that lack known genetic drivers and are therefore difficult to treat.

Hepatic Sinusoidal Obstruction Syndrome in a child after chemotherapy for medulloblastoma

Hepatic Sinusoidal Obstruction Syndrome (HSOS), the new name given to veno-occlusive disease (VOD) of the liver, is a well-known complication of high-dose chemotherapy employed with hematopoietic stem cell transplantation, but it has rarely been observed in children who receive conventional chemotherapy. HSOS following standard chemotherapy has been reported in patients receiving vincristine, actinomycin D, and cyclophosphamide for the treatment of Wilms tumor and more rarely rhabdomyosarcoma. We report a 14-year-old boy with high risk medulloblastoma treated with craniospinal radiation followed by chemotherapy, who experienced severe HSOS after only one course of chemotherapy including carboplatin, vincristine, and cyclophosphamide. To our knowledge, this is the second report of HSOS after standard dose chemotherapy for brain tumor in childhood.

Long-term neuropsychological follow-up of young children with medulloblastoma treated with sequential high-dose chemotherapy and irradiation sparing approach

High-dose chemotherapy (HDC) strategies were developed in brain tumor protocols for young children to prevent neuropsychological (NP) impairments associated with radiotherapy. However, comprehensive NP evaluations of these children treated with such strategies remain limited. We examined the long-term neurocognitive outcomes of young children (<6 years) with medulloblastoma, treated similarly, with a HDC strategy “according to” the chemotherapy regimen of the protocol CCG 99703. This retrospective study included young children less than 6 years of age at diagnosis of medulloblastoma treated from 1998 to 2011 at 7 North American institutions. Twenty-four patients who had at least one NP assessment post-treatment are the focus of the current study. Of 24 patients in this review, 15 (63%) were male and the mean age at diagnosis was 29.4 months (SD = 13.5). Posterior fossa syndrome (PFs) was reported in five patients (21%). Nine (37.5%) received radiotherapy (5 focal, 4 craniospinal). On average, children were assessed 3.5 years (SD = 1.8) post-diagnosis, and full-scale intellectual quotient (FSIQ) scores ranged from 56 to 119 (