High-grade Pediatric Brain Tumors Research Articles

Treatment Strategies in Diffuse Midline Gliomas With the H3K27M Mutation: The Role of Convection-Enhanced Delivery in Overcoming Anatomic Challenges.

Diffuse midline gliomas harboring the H3 K27M mutation—including the previously named diffuse intrinsic pontine glioma (DIPG)—are lethal high-grade pediatric brain tumors that are inoperable and without cure. Despite numerous clinical trials, the prognosis remains poor, with a median survival of ~1 year from diagnosis. Systemic administration of chemotherapeutic agents is often hindered by the blood brain barrier (BBB), and even drugs that successfully cross the barrier may suffer from unpredictable distributions. The challenge in treating this deadly disease relies on effective delivery of a therapeutic agent to the bulk tumor as well as infiltrating cells. Therefore, methods that can enhance drug delivery to the brain are of great interest. Convection-enhanced delivery (CED) is a strategy that bypasses the BBB entirely and enhances drug distribution by applying hydraulic pressure to deliver agents directly and evenly into a target region. This technique reliably distributes infusate homogenously through the interstitial space of the target region and achieves high local drug concentrations in the brain. Moreover, recent studies have also shown that continuous delivery of drug over an extended period of time is safe, feasible, and more efficacious than standard single session CED. Therefore, CED represents a promising technique for treating midline tumors with the H3K27M mutation.

Arterial spin labelling and diffusion-weighted imaging in paediatric brain tumours.

BackgroundDiffusion- and perfusion-weighted MRI are valuable tools for measuring the cellular and vascular properties of brain tumours. This has been well studied in adult patients, however, the biological features of childhood brain tumours are unique, and paediatric-focused studies are less common. We aimed to assess the diagnostic utility of apparent diffusion coefficient (ADC) values derived from diffusion-weighted imaging (DWI) and cerebral blood flow (CBF) values derived from arterial spin labelling (ASL) in paediatric brain tumours.MethodsWe performed a meta-analysis of published studies reporting ADC and ASL-derived CBF values in paediatric brain tumours. Data were combined using a random effects model in order to define typical parameter ranges for different histological tumour subtypes and WHO grades. New data were also acquired in a ‘validation cohort’ at our institution, in which ADC and CBF values in treatment naïve paediatric brain tumour patients were measured, in order to test the validity of the findings from the literature in an un-seen cohort. ADC and CBF quantification was performed by two radiologists via manual placement of tumour regions of interest (ROIs), in addition to an automated approach to tumour ROI placement.ResultsA total of 14 studies met the inclusion criteria for the meta-analysis, constituting data acquired in 542 paediatric patients. Parameters of interest were based on measurements from ROIs placed within the tumour, including mean and minimum ADC values (ADCROI-mean, ADCROI-min) and the maximum CBF value normalised to grey matter (nCBFROI-max). After combination of the literature data, a number of histological tumour subtype groups showed significant differences in ADC values, which were confirmed, where possible, in our validation cohort of 32 patients. In both the meta-analysis and our cohort, diffuse midline glioma was found to be an outlier among high-grade tumour subtypes, with ADC and CBF values more similar to the low-grade tumours. After grouping patients by WHO grade, significant differences in grade groups were found in ADCROI-mean, ADCROI-min, and nCBFROI-max, in both the meta-analysis and our validation cohort. After excluding diffuse midline glioma, optimum thresholds (derived from ROC analysis) for separating low/high-grade tumours were 0.95 × 10−3 mm2/s (ADCROI-mean), 0.82 × 10−3 mm2/s (ADCROI-min) and 1.45 (nCBFROI-max). These thresholds were able to identify low/high-grade tumours with 96%, 83%, and 83% accuracy respectively in our validation cohort, and agreed well with the results from the meta-analysis. Diagnostic power was improved by combining ADC and CBF measurements from the same tumour, after which 100% of tumours in our cohort were correctly classified as either low- or high-grade (excluding diffuse midline glioma).ConclusionADC and CBF values are useful for differentiating certain histological subtypes, and separating low- and high-grade paediatric brain tumours. The threshold values presented here are in agreement with previously published studies, as well as a new patient cohort. If ADC and CBF values acquired in the same tumour are combined, the diagnostic accuracy is optimised.

Surveillance imaging for high-grade childhood brain tumors: What to do 10 years after completion of treatment?

Brain tumors are the second most common childhood cancer. Treatment protocols for high-grade pediatric brain tumors recommend regular follow-up imaging for up to 10 years. We review maximal time to recurrence and minimal time to radiologically detectable long-term sequelae such as secondary malignancies, vascular complications, and white matter disease. No tumors recurred after the 10-year point, but radiological long-term sequelae grew more common as the treatment completion date receded. We do not recommend regular imaging more than 10 years after treatment has ended, unless there are clinical symptoms.

Abstract 4637: Tumor treating fields (TTFields) have antiproliferative effects on high-grade pediatric brain tumor cell lines

Abstract Introduction Approximately 400 children in the UK are diagnosed with a CNS tumor each year, which represents a quarter of childhood cancer cases in the UK. The 5-year survival rate of paediatric brain tumor patients is approximately 75%, but survival remains much worse for some brain tumor patients, particularly high-grade gliomas. Pre-clinical and clinical studies have demonstrated efficacy of TTFields as a treatment for high-grade glioma leading to the approval of TTFields for adult Glioblastoma multiforme (GBM) patients. The lack of overlapping toxicities associated with TTFields has made electric field therapy an attractive treatment strategy for poor prognosis paediatric brain tumors.Methods The inovitro is the laboratory based testing system used to deliver TTFields to cell cultures. inovitro was used to deliver TTFields over 72 hours at a range of clinically relevant frequencies (100-400kHz) to our panel of paediatric GBM, Medulloblastoma and Ependymoma cell lines. The effects of TTFields on cell viability and cell cycle was assessed using Resazurin based metabolic viability tests and flow cytometry. The determined optimal frequency for each cell line was also combined with a mitotic inhibitor to explore synergistic effects. Gene expression changes of TTFields treated cells was investigated. Results TTFields treatment reduces cell viability of all cell lines tested within the frequency panel. The optimum frequencies were between 100 and 400kHz for all cell lines tested. TTFields treatment had effects on cell cycling with increased G2 accumulation of treated cells being observed. Combining TTFields with mitotic inhibitors increased efficacy in an additive fashion. Conclusions This preliminary study has demonstrated efficacy of TTFields on paediatric brain tumor cell lines. The optimal frequencies for all the paediatric GBM cell lines used did not match the 200kHz as previously reported for U-87 MG cells. This report warrants further study into the potential for TTFields therapy for paediatric brain tumor patients. Citation Format: Joshua Branter, Maria Estevez-Cebrero, Richard Grundy, Surajit Basu, Stuart Smith. Tumor treating fields (TTFields) have antiproliferative effects on high-grade pediatric brain tumor cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4637.

Multiparametric Analysis of Permeability and ADC Histogram Metrics for Classification of Pediatric Brain Tumors by Tumor Grade

Accurate tumor grading is essential for treatment planning of pediatric brain tumors. We hypothesized that multiparametric analyses of a combination of permeability metrics and ADC histogram metrics would differentiate high- and low-grade tumors with high accuracy. DTI and dynamic contrast-enhanced MR imaging using T1-mapping with flip angles of 2°, 5°, 10°, and 15°, followed by a 0.1-mmol/kg body weight gadolinium-based bolus was performed on all patients in addition to standard MR imaging. Permeability data were processed and transfer constant from the blood plasma into the extracellular extravascular space, rate constant from the extracellular extravascular space back into blood plasma, extravascular extracellular volume fraction, and fractional blood plasma volume were calculated from 3D tumor volumes. Apparent diffusion coefficient histogram metrics were calculated for 3 separate tumor volumes derived from T2-FLAIR sequences, T1 contrast-enhanced sequences, and permeability maps, respectively. Results from 41 patients (0.3-16.76 years of age; mean, 6.22 years) with newly diagnosed contrast-enhancing brain tumors (16 low-grade; 25 high-grade) were included in the institutional review board-approved retrospective analysis. Wilcoxon tests showed a higher transfer constant from blood plasma into extracellular extravascular space and rate constant from extracellular extravascular space back into blood plasma, and lower extracellular extravascular volume fraction (P < .001) in high-grade tumors. The mean ADCs of FLAIR and enhancing tumor volumes were significantly lower in high-grade tumors (P < .001). ROC analysis showed that a combination of extravascular volume fraction and mean ADC of FLAIR volume differentiated high- and low-grade tumors with high accuracy (area under receiver operating characteristic curve = 0.918). ADC histogram metrics combined with permeability metrics differentiate low- and high-grade pediatric brain tumors with high accuracy.

Probing the Function of Oncohistones Using Mutant Transgenes and Knock-In Mutations.

Recently, frequent somatic mutations at histone genes have been detected in high grade pediatric brain tumor, chondroblastoma, and giant cell tumor of bone. These mutant histones are also termed oncohistones. Since oncohistone proteins co-exist with wild type histone proteins in cells, it is critically important to understand how they promote tumorigenesis. Here, we describe two methods to analyze the impact of these oncohistones on histone modification and epigenome, including the expression of oncohistone from a transgene and the utilization of CRISPR/Cas9 system to knock-in specific oncohistone mutations. The methods described are useful for the initial characterization of oncohistones. Other methods such as ChIP-seq and RNA-seq, which analyze the effect of oncohistone mutations genome wide, are not detailed in this protocol.

137 Novel Genome-wide CRISPR Screen for Glioblastoma Invasion

Abstract INTRODUCTION Among high-grade pediatric brain tumors, glioblastoma multiforme (GBM) is particularly difficult to treat. Invasion of GBM cells into normal brain parenchyma renders malignant cells inaccessible to surgical intervention and poised to drive tumor recurrence. In order to better understand the molecular mechanisms and signaling pathways underlying pediatric GBM cell invasion we performed a genome-wide CRISPR/Cas9 loss of function screen for genes that inhibit invasion. METHODS CRISPR/Cas9 is an emerging technology for genome editing that can be used to knock out genes that are targeted by short RNA guide sequences (sgRNAs). First, we made an immortalized human glioma line that stably expresses the RNA-guided DNA endonuclease, Cas9, and showed that Cas9 is functional in these cells. We then used a pooled approach to knock-out individual genes on a genome-wide scale in the Cas9 GBM cell line. Pooled cells were subjected to a Boyden chamber invasion assay which separated the cell populations based on invasive phenotype. To determine which genes were enriched in the invasive cell fraction compared to the noninvasive cell population we used next generation sequencing of the sgRNAs isolated and amplified from each group. RESULTS &gt;Analysis of sgRNA enrichment in invasive compared to noninvasive cell populations identified specific genes expected to be altered in migration, such as those involved with actin based cell projections, as well as novel candidate genes. We are currently testing the necessity and sufficiency of these genes for glioma invasion in vitro and in vivo using a xenograft mouse model. CONCLUSION In this study, we identified critical genes necessary for GBM invasion using a novel genome-wide knock-out approach. Once validated, the genes of interest may serve as prognostic surveillance markers or targets for therapeutic intervention in pediatric glioblastoma.

Automated Processing of Dynamic Contrast-Enhanced MRI: Correlation of Advanced Pharmacokinetic Metrics with Tumor Grade in Pediatric Brain Tumors.

Pharmacokinetic parameters from dynamic contrast-enhanced MR imaging have proved useful for differentiating brain tumor grades in adults. In this study, we retrospectively reviewed dynamic contrast-enhanced perfusion data from children with newly diagnosed brain tumors and analyzed the pharmacokinetic parameters correlating with tumor grade. Dynamic contrast-enhanced MR imaging data from 38 patients were analyzed by using commercially available software. Subjects were categorized into 2 groups based on pathologic analyses consisting of low-grade (World Health Organization I and II) and high-grade (World Health Organization III and IV) tumors. Pharmacokinetic parameters were compared between the 2 groups by using linear regression models. For parameters that were statistically distinct between the 2 groups, sensitivity and specificity were also estimated. Eighteen tumors were classified as low-grade, and 20, as high-grade. Transfer constant from the blood plasma into the extracellular extravascular space (Ktrans), rate constant from extracellular extravascular space back into blood plasma (Kep), and extracellular extravascular volume fraction (Ve) were all significantly correlated with tumor grade; high-grade tumors showed higher Ktrans, higher Kep, and lower Ve. Although all 3 parameters had high specificity (range, 82%-100%), Kep had the highest specificity for both grades. Optimal sensitivity was achieved for Ve, with a combined sensitivity of 76% (compared with 71% for Ktrans and Kep). Pharmacokinetic parameters derived from dynamic contrast-enhanced MR imaging can effectively discriminate low- and high-grade pediatric brain tumors.

A fractional motion diffusion model for grading pediatric brain tumors.

ObjectivesTo demonstrate the feasibility of a novel fractional motion (FM) diffusion model for distinguishing low- versus high-grade pediatric brain tumors; and to investigate its possible advantage over apparent diffusion coefficient (ADC) and/or a previously reported continuous-time random-walk (CTRW) diffusion model.Materials and methodsWith approval from the institutional review board and written informed consents from the legal guardians of all participating patients, this study involved 70 children with histopathologically-proven brain tumors (30 low-grade and 40 high-grade). Multi-b-value diffusion images were acquired and analyzed using the FM, CTRW, and mono-exponential diffusion models. The FM parameters, Dfm, φ, ψ (non-Gaussian diffusion statistical measures), and the CTRW parameters, Dm, α, β (non-Gaussian temporal and spatial diffusion heterogeneity measures) were compared between the low- and high-grade tumor groups by using a Mann-Whitney-Wilcoxon U test. The performance of the FM model for differentiating between low- and high-grade tumors was evaluated and compared with that of the CTRW and the mono-exponential models using a receiver operating characteristic (ROC) analysis.ResultsThe FM parameters were significantly lower (p < 0.0001) in the high-grade (Dfm: 0.81 ± 0.26, φ: 1.40 ± 0.10, ψ: 0.42 ± 0.11) than in the low-grade (Dfm: 1.52 ± 0.52, φ: 1.64 ± 0.13, ψ: 0.67 ± 0.13) tumor groups. The ROC analysis showed that the FM parameters offered better specificity (88% versus 73%), sensitivity (90% versus 82%), accuracy (88% versus 78%), and area under the curve (AUC, 93% versus 80%) in discriminating tumor malignancy compared to the conventional ADC. The performance of the FM model was similar to that of the CTRW model.ConclusionsSimilar to the CTRW model, the FM model can improve differentiation between low- and high-grade pediatric brain tumors over ADC.

Differentiating low‐ and high‐grade pediatric brain tumors using a continuous‐time random‐walk diffusion model at high b‐values

To demonstrate that a continuous-time random-walk (CTRW) diffusion model can improve diagnostic accuracy of differentiating low- and high-grade pediatric brain tumors. Fifty-four children with histopathologically confirmed brain tumors underwent diffusion MRI scans at 3Twith 12 b-values (0-4000 s/mm(2) ). The diffusion imageswere fit to a simplified CTRW model to extract anomalous diffusion coefficient, Dm , and temporal and spatial heterogeneity parameters, α and β, respectively. Using histopathology results as reference, a k-means clustering algorithm and a receiver operating characteristic (ROC) analysis were employed to determine the sensitivity, specificity, and diagnostic accuracy of the CTRW parameters in differentiating tumor grades. Significant differences between the low- and high-grade tumors were observed in the CTRW parameters (p-values<0.001). The k-means analysis showed that the combination of three CTRW parameters produced higher diagnostic accuracy (85% vs. 75%) and specificity (83% vs. 54%) than the apparent diffusion coefficient (ADC) from a mono-exponential model. The ROC analysis revealed that any combination of the CTRW parameters gave a larger area under the curve (0.90-0.96) than using ADC (0.80). With its sensitivity to intravoxel heterogeneity, the simplified CTRW model is useful for non-invasive grading of pediatric brain tumors, particularly when surgical biopsy is not feasible. Magn Reson Med 76:1149-1157, 2016. © 2015 Wiley Periodicals, Inc.

Analysis of T2 signal intensity helps in the differentiation between high and low-grade brain tumours in paediatric patients

Previous studies hypothesized that the analysis of magnetic resonance intensity of the solid portion in paediatric tumours can provide pre-surgical information about the histopathology. Classically, high signal-intensity in T2weighted (T2w) images identifies low-grade tumours, while anaplasia is characterized by T2 hypointensity. We aimed to investigate if T2w signal intensities can pre-operatively distinguish between low-grade and high-grade brain tumours in paediatric patients. Two raters, blinded to the histological diagnosis, rated the signal intensity of MR images (T2w) from 36 children with newly diagnosed brain tumours, 17 children with low-grade brain tumours and 19 children with high-grade brain tumours were included in this study. Relative T2 values were obtained by dividing the T2w values of the solid portion of the tumour by the T2w values of the vitreous humour. The best cut-off point to distinguish low and high-grade paediatric brain tumours was 0.8. If the signal intensity was less than or equal to 0.8 the tumour was expected to be a high-grade tumour with a sensitivity of 100%. Prediction of a low-grade tumour was more uncertain with a sensitivity of 70.5%. Overall, 86% of the tumours would have been predicted correctly. Our data suggest that T2w signal intensities of the solid portion of brain tumours in paediatrics can pre-operatively differentiate between low-grade and high-grade tumours. In addition, T2 hypointensity may be helpful in targeting stereotactic biopsy.

Differentiation of Low- and High-Grade Pediatric Brain Tumors with High b-Value Diffusion-weighted MR Imaging and a Fractional Order Calculus Model.

To demonstrate that a new set of parameters (D, β, and μ) from a fractional order calculus (FROC) diffusion model can be used to improve the accuracy of MR imaging for differentiating among low- and high-grade pediatric brain tumors. The institutional review board of the performing hospital approved this study, and written informed consent was obtained from the legal guardians of pediatric patients. Multi-b-value diffusion-weighted magnetic resonance (MR) imaging was performed in 67 pediatric patients with brain tumors. Diffusion coefficient D, fractional order parameter β (which correlates with tissue heterogeneity), and a microstructural quantity μ were calculated by fitting the multi-b-value diffusion-weighted images to an FROC model. D, β, and μ values were measured in solid tumor regions, as well as in normal-appearing gray matter as a control. These values were compared between the low- and high-grade tumor groups by using the Mann-Whitney U test. The performance of FROC parameters for differentiating among patient groups was evaluated with receiver operating characteristic (ROC) analysis. None of the FROC parameters exhibited significant differences in normal-appearing gray matter (P ≥ .24), but all showed a significant difference (P < .002) between low- (D, 1.53 μm(2)/msec ± 0.47; β, 0.87 ± 0.06; μ, 8.67 μm ± 0.95) and high-grade (D, 0.86 μm(2)/msec ± 0.23; β, 0.73 ± 0.06; μ, 7.8 μm ± 0.70) brain tumor groups. The combination of D and β produced the largest area under the ROC curve (0.962) in the ROC analysis compared with individual parameters (β, 0.943; D,0.910; and μ, 0.763), indicating an improved performance for tumor differentiation. The FROC parameters can be used to differentiate between low- and high-grade pediatric brain tumor groups. The combination of FROC parameters or individual parameters may serve as in vivo, noninvasive, and quantitative imaging markers for classifying pediatric brain tumors.

HG-15 * TARGETED NEXT GENERATION SEQUENCING IN MALIGNANT SUPRATENTORIAL PEDIATRIC BRAIN TUMORS REVEALS ACTIONABLE MUTATIONS

BACKGROUND: Pediatric supratentorial brain tumors have been difficult to appropriately categorize using standard clinical and pathological criteria. Next generation sequencing (NGS) is a promising tool to evaluate many genes simultaneously; genomic alterations identified using NGS could improve diagnosis and identify actionable alterations. Currently, there is no data on the clinical utility of NGS in pediatric brain tumors. METHODS: Twelve formalin-fixed paraffin embedded tumor samples were retrieved from 9 patients with high-grade supratentorial pediatric brain tumors resected between 2008 and 2012. Original and relapse samples were obtained from 3 patients. DNA was extracted and analyzed on a 194 gene NGS platform that has been validated clinically for use in adult malignancies with emphasis on detection of drug targets. Genetic findings were correlated with histology and immunohistochemistry. RESULTS: We found one or more pathologic genetic variant (mutation, amplification, or deletion) in 8 of 9 (89%) of patients studied, including alterations in multiple subjects of EGFR (n = 3), PDGFRA (n = 2), CDK4 (n = 2) and CDKN2A (n = 2). An identical EGFR exon 20 insertion was identified in 2 subjects, which has not been previously described in pediatric malignancy. In addition, NGS identified mutations in genes associated with familial cancer predisposition syndromes in 5 patients, including TP53 (n = 2), PTEN, CHEK2, and MSH2. Comparison of primary to relapse samples showed additional mutations and amplifications in PDGFRA and EGFR detected solely in latter relapse samples. The single patient without actionable mutations was in one of only two long-term survivors. CONCLUSIONS: Targeted deep sequencing may be useful in rare pediatric brain tumors to identify driver mutations, suggest constitutional and familial testing for cancer predisposition syndromes, and select molecular targets worthy of further study.

OT-01 * EFFECTIVENESS OF PERFUSION AND DIFFUSION IMAGING FOR GRADING PEDIATRIC BRAIN TUMORS

PURPOSE: To prospectively evaluate the effectiveness of perfusion MRI (pMRI) and diffusion MRI (DWI/ADC) measurements in distinguishing slow-growing low-grade (LG) from fast-growing high-grade (HG) pediatric brain tumors. Brain tumors in children differ significantly from adult. Therefore, testing the utility of pMRI and DWI values as biomarkers for grading pediatric brain tumors is essential. MATERIALS AND METHODS: Following IRB approval, 40 children with new brain tumors who had signed consent and assent were prospectively recruited. MRI exams with severe artifact, lesions too small for accurate diagnosis or those that did not fall under a WHO category were excluded. Thirty-four children with untreated tumors remained (16M/18F, ages 0-23yrs). Perfusion imaging was added to the routine clinical MRI. DWI and ADC images were part of the routine clinical exam. Surgically resected tumors were classified as LG (WHO I/II) or HG (WHO III/IV). Pilocytic astrocytomas (PA) and pilocytic optic-pathway gliomas (OPG) were grouped together because they behave differently than other LG lesions. Non-tumor (NT) lesions were also evaluated. Using serial imaging, stable and non-resectable lesions were classified as LG, whereas rapidly enlarging lesions were classified as HG. Based on these criteria there were HG (n = 4), LG (n = 18), PA + OPG (n = 8), and NT (n = 4). Perfusion normalized (nRCBV) and standardized (sRCBV) relative cerebral blood volume and normalized cerebral blood flow (nRCBF) were calculated. RESULTS: The sRCBV is statistically different for HG vs LG (p = 0.022), but not for nRCBV or nRCBF. ADC can distinguish HG from PA + OPG (p = 0.012) and HG from LG (p = 0.035); however, when sRCBV and ADC are combined, there is greater statistical power for distinguishing these tumor categories (HG vs LG: p = 0.0029; HG vs PA + OPG: p = 0.0095). CONCLUSIONS: The results of this study represent the first step toward developing an imaging biomarker that will allow us to subclassify pediatric brain tumors and tailor therapy to each child.

Natural Killer Cells: A Potential Therapy for Paediatric Brain Tumours

Natural killer cells are innate immune cells that are naturally involved in tumour immunosurveillance. These cells have direct cytotoxic activity and also secrete proinflammatory cytokines upon activation. The activation of natural killer cells’ cytolytic activity is dependent on a balance between inhibitory signals and activating signals provided by the host cells. Natural killer cells do not exert their activity on healthy cells, due to interactions of inhibitory receptors with self major histocompatibility class I. Inhibition may be overcome when the cell binds tumour-associated antigens on the surface of tumour cells, resulting in the polarized release of cytolytic granules toward the target cell. Natural killer cells demonstrate particular promise for cellular therapy, as they can identify and eliminate tumours that have altered major histocompatibility class I expression. Central nervous system tumours are the second most common paediatric cancer and are associated with a high mortality rate. Many of these high-grade paediatric brain tumours have very dismal prognoses, despite standard treatment regimens, and patients would substantially benefit from a novel type of therapy. Natural killer cells have been shown to be effective against many human malignancies; however, less is known about their efficacy against brain tumours. Treatment of medulloblastoma and adult glioblastoma with natural killer cells has been investigated previously and yielded promising results. Natural killer cells represent a small fraction of peripheral blood, which poses a limitation for their widespread use in adoptive cell therapy. Current research is focussed on establishing an optimal protocol for the ex vivo expansion and activation of natural killer cells. In the future, paediatric brain tumours such as glioblastoma multiforme, ependymoma and atypical teratoid/rhabdoid tumours should be examined for their susceptibility to natural killer cells.

Immunohistochemical Expression of Glypican-3 in Pediatric Tumors: An Analysis of 414 Cases

Glypican-3 (GPC3) is a proteoglycan thought to play an important role during development. Germline GPC3 mutations are seen in the rare Simpson-Golabi-Behmel syndrome (SGBS), which predisposes patients to Wilms tumor, hepatoblastoma, and neuroblastoma. While numerous adult tumors have been evaluated by immunohistochemistry for GPC3, no comprehensive assessment has been done in pediatric tumors. We therefore investigated GPC3 expression in 143 pediatric central nervous system (CNS) tumors and 271 non-CNS tumors. Among non-CNS tumors, GPC3 expression was seen in 9/9 (100%) hepatoblastomas, 4/6 (67%) malignant rhabdoid tumors, 5/13 (38%) Wilms tumors, 11/37 (30%) alveolar rhabdomyosarcomas, and 8/45 (18%) embryonal rhabdomyosarcomas. All 136 neuroblastomas, 14 Ewing sarcoma/primitive neuroectodermal tumors, and 11 synovial sarcomas were immunonegative for GPC3. Among CNS tumors, GPC3 had restricted expression, with positivity in 6/6 (100%) atypical teratoid rhabdoid tumors and 1/4 (25%) craniopharyngiomas. The remaining 136 CNS tumors-23 medulloblastomas, 21 pilocytic astrocytomas, 13 gangliogliomas, 12 ependymomas, 12 glioblastomas, 11 choroid plexus neoplasms, 10 diffuse astrocytomas (grade II/III), 10 meningiomas, 8 dysembryoplastic neuroepithelial tumors, 8 oligodendrogliomas, 3 craniopharyngiomas, 3 germinomas, and 2 neurocytomas-were entirely negative for GPC3. These results showed GPC3 positivity in a number of non-CNS tumors, with no consistent discrimination between tumors that were or were not associated with SGBS. Within the CNS, GPC3 positivity was limited to a small subset of CNS neoplasms and may thus serve as a useful positive diagnostic biomarker (P < 0.0001) in addition to negative INI1/BAF47/SMARCB1 staining to differentiate atypical teratoid rhabdoid tumors from other high-grade pediatric brain tumors.

Serial MR diffusion to predict treatment response in high-grade pediatric brain tumors: a comparison of regional and voxel-based diffusion change metrics

BackgroundAssessment of treatment response by measuring tumor size is known to be a late and potentially confounded response index. Serial diffusion MRI has shown potential for allowing earlier and possibly more reliable response assessment in adult patients, with limited experience in clinical settings and in pediatric brain cancer. We present a retrospective study of clinical MRI data in children with high-grade brain tumors to assess and compare the values of several diffusion change metrics to predict treatment response.MethodsEighteen patients (age range, 1.9–20.6 years) with high-grade brain tumors and serial diffusion MRI (pre- and posttreatment interval range, 1–16 weeks posttreatment) were identified after obtaining parental consent. The following diffusion change metrics were compared with the clinical response status assessed at 6 months: (1) regional change in absolute and normalized apparent diffusivity coefficient (ADC), (2) voxel-based fractional volume of increased (fiADC) and decreased ADC (fdADC), and (3) a new metric based on the slope of the first principal component of functional diffusion maps (fDM).ResultsResponders (n = 12) differed significantly from nonresponders (n = 6) in all 3 diffusional change metrics demonstrating higher regional ADC increase, larger fiADC, and steeper slopes (P < .05). The slope method allowed the best response prediction (P < .01, η2 = 0.78) with a classification accuracy of 83% for a slope of 58° using receiver operating characteristic (ROC) analysis.ConclusionsWe demonstrate that diffusion change metrics are suitable response predictors for high-grade pediatric tumors, even in the presence of variable clinical diffusion imaging protocols.

Differentiation between high and low grade tumours in paediatric patients by using apparent diffusion coefficients

ObjectiveThis study was performed to confirm the hypothesis that pre-operative apparent diffusion coefficient (ADC) can be used to distinguish between “low grade” and “high grade” tumours in paediatric patients. Material and methodsADC values were retrospectively evaluated in thirty-six paediatric brain tumours. Twenty-one children with low grade brain tumours (12 WHO I astrocytomas, 1 giant cell tumour, 1 pilomyxoid astrocytoma, 4 WHO II astrocytomas, 2 craniopharyngiomas and 1 ganglioglioma) and 15 children with high grade brain tumours (6 medulloblastomas, 3 WHO III ependymomas, 1 PNET, 1 malignant rhabdoid tumour, 1 malignant germ cell tumour, 1 WHO III astrocytoma, 1 WHO IV astrocytoma, 1 rhabdomyosarcoma metastasis) were included in this study. Minimum and mean ADC values were compared between low grade and high grade tumours and cut-off values were evaluated. ResultsThe cut-off values to differentiate low and high grade paediatric brain tumours were 0.7 × 10−3 mm2/s and 1.0 × 10−3 mm2/s for minimum ADC and average ADC values respectively. All but one high grade infratentorial ependymoma showed significantly lower ADC values than low grade brain tumours in children. ConclusionCombining the information obtained from conventional MR imaging with the ADC values may increase the accuracy of pre-operative differentiation between low grade and high grade paediatric tumours. Cut-off values can help to discern low from high grade tumours. However, it has to be considered that there is a substantial overlap between tumour types previously described in the literature.

Atypical Teratoid Rhabdoid Tumors (ATRTs): The British Columbia's Children's Hospital's Experience, 1986–2006

As "atypical teratoid rhabdoid tumors" (ATRTs) may mimic "small round blue cell tumors" (SRBCT), we reexamined our ATRT experience focusing upon INI-1 immunohistochemistry (IHC). All high-grade pediatric brain tumors occurring from 1986-2006 at our institution underwent INI-1 IHC. Clinicopathologic data from each INI-1 immunonegative case were reviewed. Additional genetic, epigenetic and IHC analyses (including interrogation of INI-1 and CLDN6) were performed on a subset of the INI-1 immunonegative cases. Twelve INI-1 IHC negative tumors were identified retrospectively, of which only two previously carried the diagnosis of ATRT. Overall, the clinicopathologic and genetic data supported the assertion that all 12 cases represented ATRT. Unexpectedly, three long-term survivors (4.2, 7.0 and 8.5 years) were identified. As hypothesized, "teratoid" and "rhabdoid" histologic features were relatively infrequent despite gross total resections in some cases. Methylation specific polymer chain reaction (PCR) (MSP) revealed a uniform methylation pattern across all cases and gene promoters tested (ie, MGMT, HIC1, MLH3 and RASSF1); notably, all cases demonstrated unmethylated MGMT promoters. Our data demonstate that a primitive non-rhabdoid histophenotype is common among ATRTs and highlights the diagnostic importance of INI-1 IHC. Epigenetically, the MGMT promoter is usually unmethylated in ATRT, suggesting that potential temozolomide-based chemotherapy may be of limited efficacy.

The Role of Telomere Maintenance in the Spontaneous Growth Arrest of Pediatric Low-Grade Gliomas

Spontaneous tumor regression is a unique feature of pediatric low-grade gliomas (PLGG). We speculated that lack of telomere maintenance is responsible for this behavior. We first looked for evidence of telomerase activity and alternative-lengthening telomeres (ALT) in 56 PLGG. Telomerase activity was observed in 0 of 11 PLGG in contrast to 10 of 13 high-grade pediatric brain tumors. There was no ALT in 45 of 45 samples. We applied Q-FISH to eight patients whose indolent PLGG underwent two metachronous biopsies over a lag of several years. Telomere shortening was observed in the second biopsy in all tumors but not in a normal brain control (P < .0001), indicating that lack of telomere maintenance is associated with continuous telomere erosion. Based on these observations, we observed that younger PLGG patients who exhibit more aggressive and frequently recurrent tumors had significantly longer telomeres than older ones (P = .00014). Tumors with a terminal restriction fragment length of <7.5 did not recur, whereas the presence of longer telomeres (>8.0) conferred a high likelihood of late recurrences in PLGG. Our findings provide a plausible biological mechanism to explain the tendency of PLGG to exhibit growth arrest and spontaneous regression. Telomere maintenance may therefore represent the first known biologic prognostic marker in PLGG.