Proceedings of the diffuse intrinsic pontine glioma (DIPG) Toronto Think Tank: advancing basic and translational research and cooperation in DIPG

Communicating with families of young people with hard-to-treat cancers: Healthcare professionals' perspectives on challenges, skills, and training

OBJECTIVES

Hard-to-treat childhood cancers are those where standard treatment options do not exist and the prognosis is poor. Healthcare professionals (HCPs) are responsible for communicating with families about prognosis and complex experimental treatments. We aimed to identify HCPs' key challenges and skills required when communicating with families about hard-to-treat cancers and their perceptions of communication-related training.

METHODS

We interviewed Australian HCPs who had direct responsibilities in managing children/adolescents with hard-to-treat cancer within the past 24 months. Interviews were analyzed using qualitative content analysis.

RESULTS

We interviewed 10 oncologists, 7 nurses, and 3 social workers. HCPs identified several challenges for communication with families including: balancing information provision while maintaining realistic hope; managing their own uncertainty; and nurses and social workers being underutilized during conversations with families, despite widespread preferences for multidisciplinary teamwork. HCPs perceived that making themselves available to families, empowering them to ask questions, and repeating information helped to establish and maintain trusting relationships with families. Half the HCPs reported receiving no formal training for communicating prognosis and treatment options with families of children with hard-to-treat cancers. Nurses, social workers, and less experienced oncologists supported the development of communication training resources, more so than more experienced oncologists.

SIGNIFICANCE OF RESULTS

Resources are needed which support HCPs to communicate with families of children with hard-to-treat cancers. Such resources may be particularly beneficial for junior oncologists and other HCPs during their training, and they should aim to prepare them for common challenges and foster greater multidisciplinary collaboration.

Usefulness of magnetic resonance imaging characteristics in discriminating H3 K27M-mutant gliomas from wildtype gliomas in spinal cord

AIM

The aim of this study was to determine the usefulness of magnetic resonance imaging (MRI) characteristics in discriminating H3 K27M-mutant gliomas from wildtype gliomas in the spinal cord.

MATERIALS AND METHODS

Fifty-eight patients with spinal cord gliomas were enrolled in this study. The H3 K27 gene status was identified by Sanger sequencing or immunohistochemistry test of resection tumor specimens. The MR imaging characteristics were evaluated and compared between H3 K27M-mutant and wildtype gliomas using the χ2 test and the Mann-Whitney U test.

RESULTS

Of 58 recruited patients, 23 (39.7%) were diagnosed with H3 K27M-mutant glioma. The H3 K27M-mutant gliomas were found to more likely occur in men compared with wildtype gliomas (87.0% vs. 42.9%, p = 0.001). On T2-weighted MR images, the signal-to-noise ratio (SNR) of H3 K27M-mutant gliomas was significantly lower than that of wildtype gliomas (103.9 ± 72.0 vs. 168.9 ± 86.8, p < 0.001). Of 35 wildtype tumors, 60% showed well-defined margin but this feature was not found in all mutant tumors (p < 0.001). The SNR of tumors on contrast-enhanced T1-weighted images of the H3 K27M-mutant gliomas was significantly lower than that of wildtype gliomas (187.7 ± 160.4 vs. 295.1 ± 207.8, p = 0.006). Receiver operating-characteristic analysis revealed that area under curve (AUC) of combination of 1/SNR on T2-weighted images, 1/SNR on contrast-enhanced T1-weighted images, ill-defined margin, and sex reached 0.937 (95% CI, 0.873-1.000) in discriminating H3 K27M-mutant gliomas.

CONCLUSIONS

The MR imaging characteristics are valuable in discriminating H3 K27M-mutant from wildtype gliomas in the spinal cord and the combination of these imaging features with sex had a high strength in this discrimination.

Co-design of a paediatric oncology medicines database (ProCure) to support complex care provision for children with a hard-to-treat cancer

Objectives

Paediatric oncologists often encounter challenges when seeking compassionate access to off-label therapies for their patients. This study employed implementation science and co-design techniques to develop the ProCure medicines database, with the goal of streamlining the application process and addressing identified barriers in paediatric oncology.

Methods

This study utilised an exploratory qualitative research design. Seventeen healthcare providers, including oncologists, nurse consultants, and allied health professionals, participated in semi-structured interviews guided by the Consolidated Framework for Implementation Research (CFIR) and a visual process map aid. Deductive qualitative data analysis, according to the CFIR constructs, identified key barriers and facilitators. Collaborative design sessions engaged multidisciplinary teams to develop the ProCure beta version.

Results

Barriers to off-label therapy access included resource-intensive applications, time sensitive decision-making, and complex pharmaceutical information. Facilitators included Drug Access Navigators, Molecular Tumour Boards, and a multi-disciplinary approach. ProCure addressed end-user needs by centralising medicines information. Additional features suggested by healthcare providers included blood-brain-barrier penetrability data and successful application examples.

Conclusion

ProCure represents a promising solution to the challenges paediatric oncologists face in accessing off-label therapies. By centralising information, it simplifies the application process, aids decision-making, and promotes a collaborative approach to patient care. The potential of the database to stream and enhance off-label therapy access underscores its relevance in improving paediatric oncology practise. Further research and implementation efforts are warranted to assess ProCure's real-world impact and refine its features based on user feedback.

A multimodal imaging-based classification for pediatric diffuse intrinsic pontine gliomas

OBJECT

Pediatric diffuse intrinsic pontine glioma (DIPG) is a radiologically heterogeneous disease entity, here we aim to establish a multimodal imaging-based radiological classification and evaluate the outcome of different treatment strategies under this classification frame.

METHODS

This retrospective study included 103 children diagnosed with DIPGs between January 2015 and August 2018 in Beijing Tiantan Hospital (Beijing, China). Multimodal radiological characteristics, including conventional magnetic resonance imaging (MRI), diffuse tensor imaging/diffuse tensor tractography (DTI/DTT), and positron emission tomography (PET) were reviewed to construct the classification. The outcome of different treatment strategies was compared in each DIPG subgroup using Kaplan-Meier method (log-rank test) to determine the optimal treatment for specific DIPGs.

RESULTS

Four radiological DIPG types were identified: Type A ("homocentric", n=13), Type B ("ventral", n=41), Type C ("eccentric", n=37), and Type D ("dorsal", n=12). Their treatment modalities were grouped as observation (43.7%), cytoreductive surgery (CRS) plus radiotherapy (RT) (24.3%), RT alone (11.7%), and CRS alone (20.4%). CRS+RT mainly fell into type C (29.7%), followed by type B1 (21.9%) and type D (50%). Overall, CRS+RT exhibited a potential survival advantage compared to RT alone, which was more pronounced in specific type, but this did not reach statistical significance, due to limited sample size and unbalanced distribution.

CONCLUSION

We proposed a multimodality imaging-based radiological classification for pediatric DIPG, which was useful for selecting optimal treatment strategies, especially for identifying candidates who may benefit from CRS plus RT. This classification opened a window into image-guided integrated treatment for pediatric DIPG.

Radiomic Features Based on MRI Predict Progression-Free Survival in Pediatric Diffuse Midline Glioma/Diffuse Intrinsic Pontine Glioma

Purpose: Biopsy-based assessment of H3 K27 M status helps in predicting survival, but biopsy is usually limited to unusual presentations and clinical trials. We aimed to evaluate whether radiomics can serve as prognostic marker to stratify diffuse intrinsic pontine glioma (DIPG) subsets. Methods: In this retrospective study, diagnostic brain MRIs of children with DIPG were analyzed. Radiomic features were extracted from tumor segmentations and data were split into training/testing sets (80:20). A conditional survival forest model was applied to predict progression-free survival (PFS) using training data. The trained model was validated on the test data, and concordances were calculated for PFS. Experiments were repeated 100 times using randomized versions of the respective percentage of the training/test data. Results: A total of 89 patients were identified (48 females, 53.9%). Median age at time of diagnosis was 6.64 years (range: 1-16.9 years) and median PFS was 8 months (range: 1-84 months). Molecular data were available for 26 patients (29.2%) (1 wild type, 3 K27M-H3.1, 22 K27M-H3.3). Radiomic features of FLAIR and nonenhanced T1-weighted sequences were predictive of PFS. The best FLAIR radiomics model yielded a concordance of .87 [95% CI: .86-.88] at 4 months PFS. The best T1-weighted radiomics model yielded a concordance of .82 [95% CI: .8-.84] at 4 months PFS. The best combined FLAIR + T1-weighted radiomics model yielded a concordance of .74 [95% CI: .71-.77] at 3 months PFS. The predominant predictive radiomic feature matrix was gray-level size-zone. Conclusion: MRI-based radiomics may predict progression-free survival in pediatric diffuse midline glioma/diffuse intrinsic pontine glioma.

Venetoclax cooperates with ionizing radiation to attenuate Diffuse Midline Glioma tumor growth

PURPOSE

Tumor relapse after radiation therapy (RT) is a major hurdle in treating pediatric H3K27M-mutant diffuse midline gliomas (DMGs). RT-induced stress increases association of BCL2 family of proteins with BH3 pro-apoptotic activators preventing apoptosis. We hypothesized that inhibition of RT-induced BCL2 with a clinically relevant inhibitor, venetoclax, will block BCL2 activity leading to increased apoptosis. BCL2 has never been implicated in DMG as a RT-induced resistant mechanism.

EXPERIMENTAL DESIGN

We performed an integrated genomic analysis to determine genes responsible for radioresistance and a targeted drug screen to identify drugs that synergize with radiation in DMG. Effect of venetoclax on radiation-na�ve and 6Gy radiation on cells was evaluated by studying cell death, changes in BCL2 phosphorylation, reactive oxygen species (ROS), and apoptosis, as well as BCL2 association with BH3 apoptosis initiators. The efficacy of combining venetoclax with radiation was evaluated in vivo using orthotopic xenograft models.

RESULTS

BCL2 was identified as a key regulator of tumor growth after radiation in DMGs. Radiation sensitizes DMGs to venetoclax treatment independent of p53 status. Venetoclax as a monotherapy was not cytotoxic to DMG cells. Post-radiation venetoclax treatment significantly increased cell death, reduced BCL2-BIM association and augmented mitochondrial ROS leading to increased apoptosis. Combining venetoclax with RT significantly enhanced the survival of mice with DMG tumors.

CONCLUSIONS

This study shows that venetoclax impedes the anti-apoptotic function of radiation-induced BCL2 in DMG leading to increased apoptosis. Results from these pre-clinical studies demonstrate the potential use of the BCL2 inhibitor, venetoclax, combined with RT for pediatric DMG.

New Developments in the Pathogenesis, Therapeutic Targeting, and Treatment of H3K27M-Mutant Diffuse Midline Glioma

H3K27M-mutant diffuse midline gliomas (DMGs) are rare childhood central nervous system tumors that carry a dismal prognosis. Thus, innovative treatment approaches are greatly needed to improve clinical outcomes for these patients. Here, we discuss current trends in research of H3K27M-mutant diffuse midline glioma. This review highlights new developments of molecular pathophysiology for these tumors, as they relate to epigenetics and therapeutic targeting. We focus our discussion on combinatorial therapies addressing the inherent complexity of treating H3K27M-mutant diffuse midline gliomas and incorporating recent advances in immunotherapy, molecular biology, genetics, radiation, and stereotaxic surgical diagnostics.

Emerging Advances in Combinatorial Treatments of Epigenetically Altered Pediatric High-Grade H3K27M Gliomas

Somatic mutations in histone encoding genes result in gross alterations in the epigenetic landscape. Diffuse intrinsic pontine glioma (DIPG) is a pediatric high-grade glioma (pHGG) and one of the most challenging cancers to treat, with only 1% surviving for 5 years. Due to the location in the brainstem, DIPGs are difficult to resect and rapidly turn into a fatal disease. Over 80% of DIPGs confer mutations in genes coding for histone 3 variants (H3.3 or H3.1/H3.2), with lysine to methionine substitution at position 27 (H3K27M). This results in a global decrease in H3K27 trimethylation, increased H3K27 acetylation, and widespread oncogenic changes in gene expression. Epigenetic modifying drugs emerge as promising candidates to treat DIPG, with histone deacetylase (HDAC) inhibitors taking the lead in preclinical and clinical studies. However, some data show the evolving resistance of DIPGs to the most studied HDAC inhibitor panobinostat and highlight the need to further investigate its mechanism of action. A new forceful line of research explores the simultaneous use of multiple inhibitors that could target epigenetically induced changes in DIPG chromatin and enhance the anticancer response of single agents. In this review, we summarize the therapeutic approaches against H3K27M-expressing pHGGs focused on targeting epigenetic dysregulation and highlight promising combinatorial drug treatments. We assessed the effectiveness of the epigenetic drugs that are already in clinical trials in pHGGs. The constantly expanding understanding of the epigenetic vulnerabilities of H3K27M-expressing pHGGs provides new tumor-specific targets, opens new possibilities of therapy, and gives hope to find a cure for this deadly disease.

Diffuse Gliomas of the Brainstem and Cerebellum in Adults Show Molecular Heterogeneity

Posterior fossa (PF) diffuse gliomas in pediatric patients frequently harbor the H3 K27M mutation. Among adults, PF diffuse gliomas are rare, with limited data regarding molecular features and clinical outcomes. We identified 28 adult PF diffuse glioma patients (17 males; median: 50 y, range: 19 to 78 y), with surgery performed at our institution (13 brainstem; 15 cerebellum). Histologic subtypes included anaplastic astrocytoma (n=21), glioblastoma (n=6), and diffuse astrocytoma (n=1). Immunohistochemistry was performed for H3 K27M (n=26), IDH1-R132H (n=28), and ATRX (n=28). A 150-gene neuro-oncology-targeted next-generation sequencing panel was attempted in 24/28, with sufficient informative material in 15 (51.7%). Tumors comprised 4 distinct groups: driver mutations in H3F3A (brainstem=4; cerebellum=2), IDH1 (brainstem=4; cerebellum=4), TERT promotor mutation (brainstem=0; cerebellum=3), and none of these (n=5), with the latter harboring mutations of TP53, PDGFRA, ATRX, NF1, and RB1. All TERT promoter-mutant cases were IDH-wild-type and arose within the cerebellum. To date, 20 patients have died of disease, with a median survival of 16.3 months, 1-year survival of 67.5%. Median survival within the subgroups included: H3F3A=16.4 months, IDH mutant=113.4 months, and TERT promoter mutant=12.9 months. These findings suggest that PF diffuse gliomas affecting adults show molecular heterogeneity, which may be associated with patient outcomes and possible response to therapy, and supports the utility of molecular testing in these tumors.

NTRK Fusions Can Co-Occur With H3K27M Mutations and May Define Druggable Subclones Within Diffuse Midline Gliomas

Diffuse midline gliomas (DMGs) are incurable pediatric tumors with extraordinarily limited treatment options. Decades of clinical trials combining conventional chemotherapies with radiation therapy have failed to improve these outcomes, demonstrating the need to identify and validate druggable biologic targets within this disease. NTRK1/2/3 fusions are found in a broad range of pediatric cancers, including high-grade gliomas and a subset of DMGs. Phase 1/2 studies of TRK inhibitors have demonstrated good tolerability, effective CNS penetration, and promising objective responses across all patients with TRK fusion-positive cancers, but their use has not been explored in TRK fusion-positive DMG. Here, we report 3 cases of NTRK fusions co-occurring within H3K27M-positive pontine diffuse midline gliomas. We employ a combination of single-cell and bulk transcriptome sequencing from TRK fusion-positive DMG to describe the phenotypic consequences of this co-occurring alteration. We then use ex vivo short-culture assays to evaluate the potential response to TRK inhibition in this disease. Together, these data highlight the importance of routine molecular characterization of these highly aggressive tumors and identify a small subset of patients that may benefit from currently available targeted therapies.

Standardization of the liquid biopsy for pediatric diffuse midline glioma using ddPCR

Diffuse midline glioma (DMG) is a highly morbid pediatric brain tumor. Up to 80% of DMGs harbor mutations in histone H3-encoding genes, associated with poor prognosis. We previously showed the feasibility of detecting H3 mutations in circulating tumor DNA (ctDNA) in the liquid biome of children diagnosed with DMG. However, detection of low levels of ctDNA is highly dependent on platform sensitivity and sample type. To address this, we optimized ctDNA detection sensitivity and specificity across two commonly used digital droplet PCR (ddPCR) platforms (RainDance and BioRad), and validated methods for detecting H3F3A c.83A > T (H3.3K27M) mutations in DMG CSF, plasma, and primary tumor specimens across three different institutions. DNA was extracted from H3.3K27M mutant and H3 wildtype (H3WT) specimens, including H3.3K27M tumor tissue (n = 4), CSF (n = 6), plasma (n = 4), and human primary pediatric glioma cells (H3.3K27M, n = 2; H3WT, n = 1). ctDNA detection was enhanced via PCR pre-amplification and use of distinct custom primers and fluorescent LNA probes for c.83 A > T H3F3A mutation detection. Mutation allelic frequency (MAF) was determined and validated through parallel analysis of matched H3.3K27M tissue specimens (n = 3). We determined technical nuances between ddPCR instruments, and optimized sample preparation and sequencing protocols for H3.3K27M mutation detection and quantification. We observed 100% sensitivity and specificity for mutation detection in matched DMG tissue and CSF across assays, platforms and institutions. ctDNA is reliably and reproducibly detected in the liquid biome using ddPCR, representing a clinically feasible, reproducible, and minimally invasive approach for DMG diagnosis, molecular subtyping and therapeutic monitoring.

Blood-brain barrier disruption with low-intensity pulsed ultrasound for the treatment of pediatric brain tumors: a review and perspectives

Pediatric brain tumors are the most common solid tumor and the first cause of cancer death in childhood, adolescence, and young adulthood. Current treatments are far from optimal in most of these tumors and the prognosis remains dismal for many of them. One of the main causes of the failure of current medical treatments is in part due to the existence of the blood-brain barrier (BBB), which limits drug delivery to tumors. Opening of the BBB with low-intensity pulsed ultrasound (LIPU) has emerged during the last 2 decades as a promising technique for enhancing drug delivery to the brain. In preclinical models, enhanced delivery of a wide range of therapeutic agents, from low-molecular-weight drugs, to antibodies and immune cells, has been observed as well as tumor control and increased survival. This technique has recently entered clinical trials with extracranial and intracranial devices. The safety and feasibility of this technique has furthermore been shown in patients treated monthly for recurrent glioblastoma receiving carboplatin chemotherapy. In this review, the characteristics of the BBB in the most common pediatric brain tumors are reviewed. Then, principles and mechanisms of BBB disruption with ultrasound (US) are summarized and described at the histological and biological levels. Lastly, preclinical studies that have used US-induced BBB opening in tumor models, recent clinical trials, and the potential use of this technology in pediatrics are provided.

The Prognostic Impact of Radiotherapy in Conjunction with Temozolomide in Diffuse Intrinsic Pontine Glioma: A Systematic Review and Meta-Analysis

OBJECTIVE

Diffuse intrinsic pontine glioma (DIPG) is a rare and devastating brainstem glioma that occurs predominately in children. To date, the prognostic impact of radiotherapy (RT) in conjunction with temozolomide (TMZ) in DIPG has not been thoroughly analyzed. The aim of this meta-analysis was to analyze the effectiveness of RT quantitatively and precisely in conjunction with TMZ in improving the prognosis of DIPG.

METHODS

A systematic search of 8 electronic databases was conducted. Articles mainly discussing the prognostic impact of RT in conjunction with TMZ in DIPG were selected. The pooled 1- and 2-year overall survival (OS) and progression-free survival (PFS) were calculated.

RESULTS

A total of 14 studies fulfilled our inclusion criteria, involving 283 cases of patients with DIPG who were treated with RT in conjunction with TMZ. The pooled 1- and 2-year OS of this treatment was 43% and 11%, respectively. The pooled 1- and 2-year PFS was 20% and 2%, respectively. Subgroup analysis revealed that the heterogeneity remained almost the same in all stratum. Egger's test demonstrated that the possibility of publication bias was low.

CONCLUSIONS

Requirements of up-to-date evidence on evaluating the prognostic impact of this therapy are urgent.

Safety and efficacy of brainstem biopsy in children and young adults

OBJECTIVE

Biopsies of brainstem lesions are performed to establish a diagnosis in the setting of an atypical clinical or radiological presentation, or to facilitate molecular studies. A better understanding of the safety and diagnostic yield of brainstem biopsies would help guide appropriate patient selection.

METHODS

All patients who underwent biopsy of a brainstem lesion during the period from January 2011 to June 2019 were reviewed. Demographic, radiological, surgical, and outcome data were collected.

RESULTS

A total of 58 patients underwent 65 brainstem biopsies during the study period. Overall, the median age was 7.6 years (IQR 3.9-14.2 years). Twenty-two of the 65 biopsies (34%) were open, 42 (65%) were stereotactic, and 1 was endoscopic. In 3 cases (5%), a ventriculoperitoneal shunt was placed, and in 9 cases (14%), a posterior fossa decompression was performed during the same operative session as the biopsy. An intraoperative MRI (iMRI) was performed in 28 cases (43%). In 3 of these cases (11%), the biopsy was off target and additional samples were obtained during the same procedure. New neurological deficits were noted in 5 cases (8%), including sensory deficits, ophthalmoparesis/nystagmus, facial weakness, and hearing loss; these deficits persisted in 2 cases and were transient in 3 cases. A pseudomeningocele occurred in 1 patient; no patients developed a CSF leak or infection. In 8 cases (13%) an additional procedure was needed to obtain a diagnosis.

CONCLUSIONS

Brainstem biopsies are safe and effective. Target selection and approach should be a collaborative effort. iMRI can be used to assess biopsy accuracy in real time, thereby allowing any adjustment if necessary.

Senescence Induced by BMI1 Inhibition Is a Therapeutic Vulnerability in H3K27M-Mutant DIPG

Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.

Noncoding RNAs as potential biomarkers for DIPG diagnosis and prognosis: XIST and XIST-210 involvement

PURPOSE

Diffuse intrinsic pontine gliomas (DIPGs) are the most fatal primary brainstem tumors in pediatric patients. The identification of new molecular features, mediating their formation and progression, as non-coding RNAs (ncRNAs), would be of great importance for the development of effective treatments.

METHODS

We analyzed the DIPGs transcriptome with the HTA2.0 array and it was compared with pediatric non-brainstem astrocytoma expression profiles (GSE72269).

RESULTS

More than 50% of the differentially expressed transcripts were ncRNAs and based on this, we proposed a DIPGs ncRNA signature. LncRNAs XIST and XIST-210, and the HBII-52 and HBII-85 snoRNA clusters were markedly downregulated in DIPGs. qPCR assays demonstrated XIST downregulation in all non-brainstem astrocytomas, in a gender, age, and brain location-independent manner, as well as in DIPGs affecting boys; however, DIPGs affecting girls showed both downregulation and upregulation of XIST. Girls' with longer survival positively correlated with XIST expression.

CONCLUSIONS

The involvement of ncRNAs in DIPGs is imminent and their expression profile is useful to differentiate them from non-neoplastic tissues and non-brain stem astrocytomas, which suggests their potential use as DIPG biomarkers. In fact, XIST and XIST-210 are potential DIPG prognostic biomarkers.

Impact of histological diagnosis on the treatment of atypical brainstem lesions

For atypical brainstem lesions, histological diagnosis can have an impact on treatment, especially in cases where diffuse glioma is not found. Since radiotherapy is the only therapeutic modality that has shown clinical and radiographic improvement in patients with diffuse glioma, the misdiagnosis of diffuse glioma can have drastic consequences, particularly in patients with nontumorous lesions. Thus, the purpose of this study was to evaluate the impact of histological diagnosis on the treatment of atypical brainstem lesions. This was a retrospective study of 31 patients who underwent biopsy of atypical brainstem lesions. The procedures were performed between January 2008 and December 2018 at the Life Center Hospital and Santa Casa de Belo Horizonte, MG, Brazil. A diagnosis was obtained in 26 (83.9%) cases. Three patients presented complications: one presented bleeding with no clinical repercussions and two showed worsening of neurological deficit, only one of which was definitive. No mortality occurred due to the procedure. The histological diagnosis was diffuse glioma in seven cases (22.6%) and not diffuse glioma in 19 cases (61.3%). Thus, the histological diagnosis had an impact on the treatment of 19 patients (treatment impact rate: 61.3%). The histological diagnosis of intrinsic brainstem lesions is a safe, efficient procedure with a high diagnosis rate, and as such, it should be considered in the management of atypical lesions.

ALK2: A Therapeutic Target for Fibrodysplasia Ossificans Progressiva and Diffuse Intrinsic Pontine Glioma

Fibrodysplasia ossificans progressiva (FOP) and diffuse intrinsic pontine glioma (DIPG) are diseases that typically manifest in childhood and are associated with severely reduced life expectancy. However, there are currently no effective therapies for these diseases, which remain incurable. Activin receptor-like kinase-2 (ALK2), encoded by the ACVR1 gene, is a bone morphogenetic protein (BMP) type-I receptor subtype that plays an important physiological role in the development of bones, muscles, brain, and other organs. Constitutively active mutants of ALK2 have been identified as causative of FOP and involved in the tumorigenesis of DIPG owing to abnormal activation of BMP signaling, and therefore have emerged as promising treatment targets. Here, we describe these two diseases, along with the link to ALK2 signal transduction, and highlight potential ALK2 inhibitors that are under development to offer new hope for patients with FOP and DIPG.

Super Elongation Complex as a Targetable Dependency in Diffuse Midline Glioma

Histone 3 gene mutations are the eponymous drivers in diffuse midline gliomas (DMGs), aggressive pediatric brain cancers for which no curative therapy currently exists. These recurrent oncohistones induce a global loss of repressive H3K27me3 residues and broad epigenetic dysregulation. In order to identify therapeutically targetable dependencies within this disease context, we performed an RNAi screen targeting epigenetic/chromatin-associated genes in patient-derived DMG cultures. This identified AFF4, the scaffold protein of the super elongation complex (SEC), as a molecular dependency in DMG. Interrogation of SEC function demonstrates a key role for maintaining clonogenic potential while promoting self-renewal of tumor stem cells. Small-molecule inhibition of SEC using clinically relevant CDK9 inhibitors restores regulatory RNA polymerase II pausing, promotes cellular differentiation, and leads to potent anti-tumor effect both in vitro and in patient-derived xenograft models. These studies present a rationale for further exploration of SEC inhibition as a promising therapeutic approach to this intractable disease.

Ultrasound-induced blood-brain barrier disruption for the treatment of gliomas and other primary CNS tumors

The treatment of primary brain tumors, especially malignant gliomas, remains challenging. The failure of most treatments for this disease is partially explained by the blood-brain barrier (BBB), which prevents circulating molecules from entering the brain parenchyma. Ultrasound-induced BBB disruption (US-BBBD) has recently emerged as a promising strategy to improve the delivery of therapeutic agents to brain tumors. A large body of preclinical studies has demonstrated that the association of low-intensity pulsed ultrasound with intravenous microbubbles can transiently open the BBB in a localized manner. The safety of this technique has been assessed in numerous preclinical studies in both small and large animal models. A large panel of therapeutic agents have been delivered to the brain in preclinical models, demonstrating both tumor control and increased survival. This technique has recently entered clinical trials with encouraging preliminary data. In this review, we describe the mechanisms and histological effects of US-BBBD and summarize the preclinical studies published to date. We furthermore provide an overview of the current clinical development and future potential of this promising technology.

Pediatric diffuse intrinsic pontine glioma: where do we stand?

Pediatric diffuse intrinsic pontine glioma (DIPG) represents approximately 20% of all pediatric CNS tumors. However, disease outcomes are dismal with a median survival of less than 1 year and a 2-year overall survival rate of less than 10%. Despite extensive efforts to improve survival outcomes, progress towards clinical improvement has been largely stagnant throughout the last 4 decades. Focal radiotherapy remains the standard of care with no promising single-agent alternatives and no evidence for improvement with the addition of a long list of systemic therapies. A better understanding of the biology of DIPG, though not easy due to obstacles in obtaining pathological material to study, is promising for the development of specific individualized treatment for this fatal disease. Recent studies have found epigenetic mutations to be successful predictors and prognostic factors for developing future management policies. The aim of this review is to give a global overview about the epidemiology, diagnosis, and treatment of DIPG. We further examine the controversial biopsy and autopsy issue that is unique to DIPG and assess the subsequent impact this issue has on the research efforts and clinical management of DIPG.

Ventricular Cerebrospinal Fluid Sampling in Pediatric Diffuse Midline Glioma Patients: Institutional Experience and Review of the Literature

Purpose: Increasing evidence suggests that circulating biomarkers may serve diagnostic and longitudinal monitoring purposes in pediatric neuro-oncology. Mutant tumor DNA is detectable in the cerebrospinal fluid (CSF) of pediatric diffuse midline glioma (DMG) patients and quantity can reflect disease burden. CSF sampling ("liquid biopsy") via a CSF access device could therefore play a role in DMG management. Therefore, we set to evaluate the incidence of hydrocephalus (HCP) in DMG patients, and to characterize ventricular reservoir placement and access practices. Methods: A single institution retrospective review of DMG patients ≤21-years-old was performed (1984-2019). MEDLINE searches for reports of ventricular reservoir or shunt placement in DMG, and reservoir access for intraventricular chemotherapy (IVC) were performed. Results: At our institution, 62.6% of DMG patients (67/108) required intervention for HCP: 19.4% provided transient CSF access (ETV alone n = 3, EVD n = 8, unspecified n = 2), and 80.6% permanent CSF access (ETV + reservoir n = 13, shunt n = 41). Further, 22/34 patients with initially transient CSF devices required conversion to a permanent device. Five devices were revised for malfunction, one for infection. Seventeen articles cited HCP in 22 to 100% of DMG patients. IVC administration was described in 632 patients (seven articles), with 42 infectious and 63 non-infectious complications. Conclusions: Management of HCP is often necessary in children with DMG. Given the low rate of clinical risk associated with VAD placement and access, and the potential utility of longitudinal disease monitoring via CSF analysis, VAD placement could be considered in future clinical trials to guide DMG treatment.

A machine learning-based prediction model of H3K27M mutations in brainstem gliomas using conventional MRI and clinical features

BACKGROUND

H3K27M is the most frequent mutation in brainstem gliomas (BSGs), and it has great significance in the differential diagnosis, prognostic prediction and treatment strategy selection of BSGs. There has been a lack of reliable noninvasive methods capable of accurately predicting H3K27M mutations in BSGs.

METHODS

A total of 151 patients with newly diagnosed BSGs were included in this retrospective study. The H3K27M mutation status was obtained by whole-exome, whole-genome or Sanger's sequencing. A total of 1697 features, including 6 clinical parameters and 1691 imaging features, were extracted from pre- and post-contrast T1-weighted and T2-weighted images. Using a random forest algorithm, 36 selected MR image features were integrated with 3 selected clinical features to generate a model that was predictive of H3K27M mutations. Additionally, a simplified prediction model comprising the Karnofsky Performance Status (KPS) at diagnosis, symptom duration at diagnosis and edge sharpness on T2 was established for practical clinical utility using the least squares estimation method.

RESULTS

H3K27M mutation was an independent prognostic factor that conferred a worse prognosis (p = 0.01, hazard ratio = 3.0, 95% confidence interval [CI], 1.57-5.74). The machine learning-based model achieved an accuracy of 84.44% (area under the curve [AUC] = 0.8298) in the test cohort. The simplified model achieved an AUC of 0.7839 in the test cohort.

CONCLUSIONS

Using conventional MRI and clinical features, we established a machine learning-based model with high accuracy and a simplified model with improved clinical utility to predict H3K27M mutations in BSGs.

Diffuse Intrinsic Pontine Glioma : Clinical Features, Molecular Genetics, and Novel Targeted Therapeutics

Diffuse intrinsic pontine glioma (DIPG) is a deadly paediatric brain cancer. Transient response to radiation, ineffective chemotherapeutic agents and aggressive biology result in rapid progression of symptoms and a dismal prognosis. Increased availability of tumour tissue has enabled the identification of histone gene aberrations, genetic driver mutations and methylation changes, which have resulted in molecular and phenotypic subgrouping. However, many of the underlying mechanisms of DIPG oncogenesis remain unexplained. It is hoped that more representative in vitro and preclinical models–using both xenografted material and genetically engineered mice–will enable the development of novel chemotherapeutic agents and strategies for targeted drug delivery. This review provides a clinical overview of DIPG, the barriers to progress in developing effective treatment, updates on drug development and preclinical models, and an introduction to new technologies aimed at enhancing drug delivery.

Effective Drug Delivery in Diffuse Intrinsic Pontine Glioma: A Theoretical Model to Identify Potential Candidates

Despite decades of clinical trials for diffuse intrinsic pontine glioma (DIPG), patient survival does not exceed 10% at two years post-diagnosis. Lack of benefit from systemic chemotherapy may be attributed to an intact bloodbrain barrier (BBB). We aim to develop a theoretical model including relevant physicochemical properties in order to review whether applied chemotherapeutics are suitable for passive diffusion through an intact BBB or whether local administration via convection-enhanced delivery (CED) may increase their therapeutic potential. Physicochemical properties (lipophilicity, molecular weight, and charge in physiological environment) of anticancer drugs historically and currently administered to DIPG patients, that affect passive diffusion over the BBB, were included in the model. Subsequently, the likelihood of BBB passage of these drugs was ascertained, as well as their potential for intratumoral administration via CED. As only non-molecularly charged, lipophilic, and relatively small sized drugs are likely to passively diffuse through the BBB, out of 51 drugs modeled, only 8 (15%)-carmustine, lomustine, erlotinib, vismodegib, lenalomide, thalidomide, vorinostat, and mebendazole-are theoretically qualified for systemic administration in DIPG. Local administration via CED might create more therapeutic options, excluding only positively charged drugs and drugs that are either prodrugs and/or only available as oral formulation. A wide variety of drugs have been administered systemically to DIPG patients. Our model shows that only few are likely to penetrate the BBB via passive diffusion, which may partly explain the lack of efficacy. Drug distribution via CED is less dependent on physicochemical properties and may increase the therapeutic options for DIPG.

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy with infiltration into other regions of the brainstem. Although large numbers of specific targeted therapies have been tested, no significant progress has been made in treating these high-grade gliomas. Therefore, the identification of new therapeutic approaches is of great importance for the development of more effective treatments. This article reviews the conventional therapies and new potential therapeutic approaches for DIPG, including epigenetic therapy, immunotherapy, and the combination of stem cells with nanoparticle delivery systems.

External validation of the diffuse intrinsic pontine glioma survival prediction model: a collaborative report from the International DIPG Registry and the SIOPE DIPG Registry

We aimed to perform external validation of the recently developed survival prediction model for diffuse intrinsic pontine glioma (DIPG), and discuss its utility. The DIPG survival prediction model was developed in a cohort of patients from the Netherlands, United Kingdom and Germany, registered in the SIOPE DIPG Registry, and includes age <3 years, longer symptom duration and receipt of chemotherapy as favorable predictors, and presence of ring-enhancement on MRI as unfavorable predictor. Model performance was evaluated by analyzing the discrimination and calibration abilities. External validation was performed using an unselected cohort from the International DIPG Registry, including patients from United States, Canada, Australia and New Zealand. Basic comparison with the results of the original study was performed using descriptive statistics, and univariate- and multivariable regression analyses in the validation cohort. External validation was assessed following a variety of analyses described previously. Baseline patient characteristics and results from the regression analyses were largely comparable. Kaplan-Meier curves of the validation cohort reproduced separated groups of standard (n = 39), intermediate (n = 125), and high-risk (n = 78) patients. This discriminative ability was confirmed by similar values for the hazard ratios across these risk groups. The calibration curve in the validation cohort showed a symmetric underestimation of the predicted survival probabilities. In this external validation study, we demonstrate that the DIPG survival prediction model has acceptable cross-cohort calibration and is able to discriminate patients with short, average, and increased survival. We discuss how this clinico-radiological model may serve a useful role in current clinical practice.

Progressive multifocal exophytic pontine glioblastoma: a case report with literature review

Multifocal pontine glioblastoma exhibiting an exophytic growth pattern in the cerebello-pontine angle (CPA) is rare. We present a case of a 5-year-old girl with consecutive neurological imaging and other clinical findings indicating progressive multifocal exophytic pontine glioblastoma. Three lesions were reported, of which two were initially presented, and one was developed 2 months later. One lesion demonstrated a progressing exophytic extension in the cistern of the left side of the CPA. The other two lesions were located and confined within the pons. Initial magnetic resonance imaging and positron emission tomography–computed tomography indicated low-grade glioma or inflammatory disease. However, 2 and 3 months later, subsequent magnetic resonance spectroscopy (MRS) displayed elevated choline and depressed N-acetyl aspartate peaks compared with the peaks on the initial MRS, indicating a high-grade glioma. Subtotal resection was performed for the CPA lesion. Histopathologic examination showed discrepant features of different parts of the CPA lesion. The patient received no further chemotherapy or radiotherapy and died 2 months after surgery. The multifocal and exophytic features of this case and the heterogeneous manifestations on neurological images were rare and confusing for both diagnosis and surgical decision-making. Our case report may contribute knowledge and helpful guidance for other medical doctors.

Brainstem Glioma in Adults

Brainstem gliomas are not nearly as common in adults as they are in children. They are likely the final common consequence not of a single disease process but of several. They can be difficult to diagnose, and are challenging to treat. Clinical studies of this diagnosis are few and generally small. Because of these factors, our understanding of the biology of adult brainstem glioma is incomplete. However, the knowledge base is growing and progress is being made. In this article, we review the current state of knowledge for brainstem glioma in adults and identify key areas for which additional information is required.

Biopsy in a series of 130 pediatric diffuse intrinsic Pontine gliomas

PURPOSE

Diffuse intrinsic pontine glioma (DIPG) is the most severe pediatric solid tumor, with no significant improvement in the past 50 years. Possible reasons for failure to make therapeutic progress include poor understanding of the underlying molecular biology due to lack of tumor material.

METHODS

We performed a prospective analysis of children with typical appearance of DIPG who had a stereotactic biopsy in our unit since 2002. Technical approach, complications, histopathological results, and samples processing are exposed. The literature on this subject is discussed.

RESULTS

Reviewing our own 130 cases of DIPG biopsies and previous published data, these procedures appear to have a diagnostic yield and morbidity rates similar to those reported for other brain locations (3.9 % of transient morbidity in our series). In addition, the quality and the quantity of the material obtained allow to (1) confirm the diagnosis, (2) reveal that WHO grading was useless to predict outcome, and (3) perform an extended molecular screen, including biomarkers study and the development of preclinical models. Recent studies reveal that DIPG may comprise more than one biological entity and a unique oncogenesis involving mutations never described in other types of cancers, i.e., histones H3 K27M and activin receptor ACVR1.

CONCLUSION

Stereotactic biopsies of DIPG can be considered as a safe procedure in well-trained neurosurgical teams and could be incorporated in protocols. It is a unique opportunity to integrate DIPG biopsies in clinical practice and use the biology at diagnosis to drive the introduction of innovative targeted therapies, in combination with radiotherapy.

Disrupting NOTCH Slows Diffuse Intrinsic Pontine Glioma Growth, Enhances Radiation Sensitivity, and Shows Combinatorial Efficacy With Bromodomain Inhibition

NOTCH regulates stem cells during normal development and stemlike cells in cancer, but the roles of NOTCH in the lethal pediatric brain tumor diffuse intrinsic pontine glioma (DIPG) remain unknown. Because DIPGs express stem cell factors such as SOX2 and MYCN, we hypothesized that NOTCH activity would be critical for DIPG growth. We determined that primary DIPGs expressed high levels of NOTCH receptors, ligands, and downstream effectors. Treatment of the DIPG cell lines JHH-DIPG1 and SF7761 with the γ-secretase inhibitor MRK003 suppressed the level of the NOTCH effectors HES1, HES4, and HES5; inhibited DIPG growth by 75%; and caused a 3-fold induction of apoptosis. Short hairpin RNAs targeting the canonical NOTCH pathway caused similar effects. Pretreatment of DIPG cells with MRK003 suppressed clonogenic growth by more than 90% and enhanced the efficacy of radiation therapy. The high level of MYCN in DIPG led us to test sequential therapy with the bromodomain inhibitor JQ1 and MRK003, and we found that JQ1 and MRK003 inhibited DIPG growth and induced apoptosis. Together, these results suggest that dual targeting of NOTCH and MYCN in DIPG may be an effective therapeutic strategy in DIPG and that adding a γ-secretase inhibitor during radiation therapy may be efficacious initially or during reirradiation.

Clinicopathology of diffuse intrinsic pontine glioma and its redefined genomic and epigenomic landscape

Diffuse intrinsic pontine glioma (DIPG) is one of the most lethal pediatric central nervous system (CNS) cancers. Recently, a surge in molecular studies of DIPG has occurred, in large part due to the increased availability of tumor tissue through donation of post-mortem specimens. These new discoveries have established DIPGs as biologically distinct from adult gliomas, harboring unique genomic aberrations. Mutations in histone encoding genes are shown to be associated with >70% of DIPG cases. However, the exact molecular mechanisms of the tumorigenicity of these mutations remain elusive. Understanding the driving mutations and genomic landscape of DIPGs can now guide the development of targeted therapies for this incurable childhood cancer.

A twenty-year review of diagnosing and treating children with diffuse intrinsic pontine glioma in The Netherlands

INTRODUCTION

Children with diffuse intrinsic pontine glioma (DIPG) face a dismal prognosis, with a median overall survival of 9 months. Our aims are to determine the incidence of DIPG in the Netherlands and to identify points for improvement in clinical research, a prerequisite for increasing the chance to find a cure.

METHODS

We performed a population-based retrospective cohort study by evaluating all children diagnosed with DIPG in the Netherlands between 1990 and 2010.

RESULTS

The incidence of DIPG in the Netherlands corresponds with international literature. Between 1990 and 2010, a large heterogeneity of treatment schedules was applied and only a minority of patients was included in clinical trials.

DISCUSSION

Given the rarity of DIPG, we emphasize the need for (inter-)national trials to facilitate the identification of potentially effective therapeutics in the future. This can be supported by the recent development of a European DIPG registry enabling international study collaborations.

Superselective intracerebral catheterization for administration of oncolytic virotherapy in a case of diffuse intrinsic pontine glioma

New therapies are needed to improve current results in diffuse intrinsic pontine glioma. We present here the initial experience of administering Celyvir, autologous mesenchymal stem cells infected with ICOVIR-5, an oncolytic adenovirus that selectively replicates in cancer cells, by means of superselective intra-arterial delivery, in a patient diagnosed of diffuse intrinsic pontine glioma. Feasibility, safety, and morbidity rates of the superselective catheterization technique are comparable with those of diagnostic angiography. The intra-arterial approach warrants a greater contact of the mesenchymal stem cells with the tumor mass, and minimizes hemorrhages or vascular disruption. The tolerance to the 2 administrations was excellent, with no acute or delayed adverse effect, underscoring the feasibility of this technique for the delivery of virotherapies and/or cellular therapies in this location.

Convection enhanced delivery of carmustine to the murine brainstem: a feasibility study

BACKGROUND

Systemic delivery of therapeutic agents remains ineffective against diffuse intrinsic pontine glioma (DIPG), possibly due to an intact blood-brain-barrier (BBB) and to dose-limiting toxicity of systemic chemotherapeutic agents. Convection-enhanced delivery (CED) into the brainstem may provide an effective local delivery alternative for DIPG patients.

NEW METHOD

The aim of this study is to develop a method to perform CED into the murine brainstem and to test this method using the chemotherapeutic agent carmustine (BiCNU). To this end, a newly designed murine CED catheter was tested in vitro and in vivo. After determination of safety and distribution, mice bearing VUMC-DIPG-3 and E98FM-DIPG brainstem tumors were treated with carmustine dissolved in DW 5% or carmustine dissolved in 10% ethanol.

RESULTS

Our results show that CED into the murine brainstem is feasible and well tolerated by mice with and without brainstem tumors. CED of carmustine dissolved in 5% DW increased median survival of mice with VUMC-DIPG-3 and E98FM-DIPG tumors with 35% and 25% respectively. Dissolving carmustine in 10% ethanol further improved survival to 45% in mice with E98FM-DIPG tumors.

COMPARISON WITH EXISTING METHODS

Since genetically engineered and primary DIPG models are currently only available in mice, murine CED studies have clear advantages over CED studies in other animals.

CONCLUSION

CED in the murine brainstem can be performed safely, is well tolerated and can be used to study efficacy of chemotherapeutic agents orthotopically. These results set the foundation for more CED studies in murine DIPG models.

Phase 2 study of safety and efficacy of nimotuzumab in pediatric patients with progressive diffuse intrinsic pontine glioma

BACKGROUND

The prognosis of diffuse intrinsic pontine glioma (DIPG) remains poor, with no drug proven to be effective.

METHODS

Patients with clinically and radiologically confirmed, centrally reviewed DIPG, who had failed standard first-line therapy were eligible for this multicenter phase II trial. The anti-epidermal growth factor receptor (EGFR) antibody, nimotuzumab (150 mg/m(2)), was administered intravenously once weekly from weeks 1 to 7 and once every 2 weeks from weeks 8 to 18. Response evaluation was based on clinical and MRI assessments. Patients with partial response (PR) or stable disease (SD) were allowed to continue nimotuzumab.

RESULTS

Forty-four patients received at least one dose of nimotuzumab (male/female, 20/24; median age, 6.0 years; range, 3.0-17.0 years). All had received prior radiotherapy. Treatment was well tolerated. Eighteen children experienced serious adverse events (SAEs). The majority of SAEs were associated with disease progression. Nineteen patients completed 8 weeks (W8) of treatment: There were 2 PRs, 6 SDs, and 11 progressions. Five patients completed 18 weeks (W18) of treatment: 1 of 2 patients with PR at W8 remained in PR at W18, and 3 of 6 children with SD at W8 maintained SD at W18. Time to progression following initiation of nimotuzumab for the 4 patients with SD or better at W18 was 119, 157, 182 and 335 days, respectively. Median survival time was 3.2 months. Two patients lived 663 and 481 days from the start of nimotuzumab.

CONCLUSIONS

Modest activity of nimotuzumab in DIPG, which has been shown previously, was confirmed: A small subset of DIPG patients appeared to benefit from anti-EGFR antibody treatment.

The expressions of Wnt/β-catenin pathway-related components in brainstem gliomas

BACKGROUND

The overall prognosis of brainstem gliomas is very poor, and the current treatment cannot significantly prolong the overall survival of these patients; therefore, studying the molecular biological mechanisms of the occurrence and development of brainstem gliomas has important significance for their treatment. The Wnt/β-catenin signaling pathway is closely associated with the occurrence and development of tumors, but its relationship with brainstem gliomas remains unclear.

METHODS

This study used Western blot and immunohistochemistry methods to detect the expressions of Wnt/β-catenin signaling pathway-related components such as Wnt-1, Wnt-2, β-catenin and C-myc in six cases of normal brain tissues and 24 cases of brainstem gliomas and analyzed the relationship between their expressions and clinicopathological characteristics.

RESULTS

Wnt-1 had no obvious expression in normal brain tissues and did not show any significant difference between high- and low-grade brainstem gliomas; the expressions of Wnt-2, β-catenin and C-myc in high-grade brainstem gliomas were significantly higher than that in low-grade brainstem gliomas and normal brain tissues and were positively correlated with the expression of Ki-67. Moreover, the expressions of Wnt-2 and C-myc were significantly associated with the prognosis of brainstem glioma patients; additionally, there was a trend toward increased β-catenin expression with shorter survival, but there was no statistical difference.

CONCLUSIONS

Wnt/β-catenin signaling pathway might be abnormally activated and plays an important role in the occurrence and development of brainstem gliomas. Wnt-2, β-catenin and C-myc may be potential targets for brainstem glioma treatment.

Diagnostic value and safety of stereotactic biopsy for brainstem tumors: a systematic review and meta-analysis of 1480 cases

BACKGROUND

The feasibility and safety of stereotactic biopsy for brainstem tumors (BSTs) are controversial. Although magnetic resonance imaging (MRI) has been reported as the preferred diagnostic tool, histopathological analysis is frequently necessary to establish a definitive diagnosis. Recent advances in molecular characterization of brainstem gliomas-accounting for the majority of BSTs-have revealed several potential targets for molecular-based therapies. Hence, a molecular stereotactic biopsy that combines histopathological diagnosis with molecular-genetic analysis will become increasingly important for patients with BSTs.

OBJECTIVE

We conducted a systemic review and meta-analysis to determine the risks and benefits of stereotactic biopsy for BSTs.

METHODS

A systematic search in PubMed, Embase, and the Web of Science yielded 3766 potentially eligible abstracts. Meta-analysis was conducted on 38 studies describing 1480 biopsy procedures for BSTs. Primary outcome measures were diagnostic success and procedure-related complications. Data were analyzed according to standard meta-analytic techniques.

RESULTS

The weighted average proportions across the analyzed studies were: 96.2% (95% confidence interval [CI]: 94.5%-97.6%) for diagnostic success, 7.8% (95% CI: 5.6%-10.2%) for overall morbidity, 1.7% (95% CI: 0.9%-2.7%) for permanent morbidity, and 0.9% (95% CI: 0.5%-1.4%) for mortality. Meta-regression revealed a significant correlation between diagnostic success rates and the number of biopsy procedures performed annually in each center (P = .011). Other factors did not affect the outcome measures.

CONCLUSION

Stereotactic biopsy of BSTs is safe. It allows exact histopathological diagnosis as a prerequisite for adequate treatment and opens new perspectives for the molecular characterization of these tumors as a crucial first step toward more individualized treatment concepts.

ABBREVIATIONS

: BST, brainstem tumorCI, confidence intervalD-BSG, diffuse brainstem gliomaHGG, high-grade gliomaLGG, low-grade gliomasTC, transcerebellarTF, transfrontal.

Comparative multidimensional molecular analyses of pediatric diffuse intrinsic pontine glioma reveals distinct molecular subtypes

Diffuse intrinsic pontine glioma (DIPG) is a highly morbid form of pediatric brainstem glioma. Here, we present the first comprehensive protein, mRNA, and methylation profiles of fresh-frozen DIPG specimens (n = 14), normal brain tissue (n = 10), and other pediatric brain tumors (n = 17). Protein profiling identified 2,305 unique proteins indicating distinct DIPG protein expression patterns compared to other pediatric brain tumors. Western blot and immunohistochemistry validated upregulation of Clusterin (CLU), Elongation Factor 2 (EF2), and Talin-1 (TLN1) in DIPGs studied. Comparisons to mRNA expression profiles generated from tumor and adjacent normal brain tissue indicated two DIPG subgroups, characterized by upregulation of Myc (N-Myc) or Hedgehog (Hh) signaling. We validated upregulation of PTCH, a membrane receptor in the Hh signaling pathway, in a subgroup of DIPG specimens. DNA methylation analysis indicated global hypomethylation of DIPG compared to adjacent normal tissue specimens, with differential methylation of 24 genes involved in Hh and Myc pathways, correlating with protein and mRNA expression patterns. Sequencing analysis showed c.83A>T mutations in the H3F3A or HIST1H3B gene in 77 % of our DIPG cohort. Supervised analysis revealed a unique methylation pattern in mutated specimens compared to the wild-type DIPG samples. This study presents the first comprehensive multidimensional protein, mRNA, and methylation profiling of pediatric brain tumor specimens, detecting the presence of two subgroups within our DIPG cohort. This multidimensional analysis of DIPG provides increased analytical power to more fully explore molecular signatures of DIPGs, with implications for evaluating potential molecular subtypes and biomarker discovery for assessing response to therapy.

Implementation of a multi-institutional diffuse intrinsic pontine glioma autopsy protocol and characterization of a primary cell culture

AIMS

Diffuse intrinsic pontine glioma (DIPG) is a fatal paediatric malignancy. Tumour resection is not possible without serious morbidity and biopsies are rarely performed. The resulting lack of primary DIPG material has made preclinical research practically impossible and has hindered the development of new therapies for this disease. The aim of the current study was to address the lack of primary DIPG material and preclinical models by developing a multi-institutional autopsy protocol.

METHODS

An autopsy protocol was implemented in the Netherlands to obtain tumour material within a brief post mortem interval. A team of neuropathologists and researchers was available at any time to perform the autopsy and process the material harvested. Whole brain autopsy was performed and primary DIPG material and healthy tissue were collected from all affected brain areas. Finally, the study included systematic evaluation by parents.

RESULTS

Five autopsies were performed. The mean time interval between death and time of autopsy was 3 h (range 2-4). All tumours were graded as glioblastoma. None of the parents regretted their choice to participate, and they all derived comfort in donating tissue of their child in the hope to help future DIPG patients. In addition, we developed and characterized one of the first DIPG cell cultures from post mortem material.

CONCLUSION

Here we show that obtaining post mortem DIPG tumour tissue for research purposes is feasible with short delay, and that the autopsy procedure is satisfying for participating parents and can be suitable for the development of preclinical DIPG models.

Brainstem glioma: a review

Brainstem gliomas (BGs) are a heterogenous group of gliomas that occur predominately in children. They can be separated into groups on the basis of anatomy and clinical behavior: diffuse intrinsic pontine glioma (DIPG), exophytic medullary glioma, and tectal glioma. DIPG is the commonest BG. Median age at onset is 6.5 years and median survival is less than 1 year. Adults with DIPG survive longer, suggesting a less aggressive and biologically different tumor from that in children. Patients present with cranial nerve dysfunction, long tract signs, or ataxia, either in isolation or in combination. Magnetic resonance imaging shows an infiltrative lesion occupying most of the pons and contrast enhancement is usually not prominent. Standard treatment is fractionated radiotherapy. Platelet-derived growth factor receptor alpha and epidermal growth factor receptor mutations have been identified. Inhibitors of these growth factor receptors are being evaluated in clinical trials. Exophytic medullary and tectal gliomas are relatively indolent tumors that can often be followed closely without treatment.

K27M mutation in histone H3.3 defines clinically and biologically distinct subgroups of pediatric diffuse intrinsic pontine gliomas

Pediatric glioblastomas (GBM) including diffuse intrinsic pontine gliomas (DIPG) are devastating brain tumors with no effective therapy. Here, we investigated clinical and biological impacts of histone H3.3 mutations. Forty-two DIPGs were tested for H3.3 mutations. Wild-type versus mutated (K27M-H3.3) subgroups were compared for HIST1H3B, IDH, ATRX and TP53 mutations, copy number alterations and clinical outcome. K27M-H3.3 occurred in 71 %, TP53 mutations in 77 % and ATRX mutations in 9 % of DIPGs. ATRX mutations were more frequent in older children (p < 0.0001). No G34V/R-H3.3, IDH1/2 or H3.1 mutations were identified. K27M-H3.3 DIPGs showed specific copy number changes, including all gains/amplifications of PDGFRA and MYC/PVT1 loci. Notably, all long-term survivors were H3.3 wild type and this group of patients had better overall survival. K27M-H3.3 mutation defines clinically and biologically distinct subgroups and is prevalent in DIPG, which will impact future therapeutic trial design. K27M- and G34V-H3.3 have location-based incidence (brainstem/cortex) and potentially play distinct roles in pediatric GBM pathogenesis. K27M-H3.3 is universally associated with short survival in DIPG, while patients wild-type for H3.3 show improved survival. Based on prognostic and therapeutic implications, our findings argue for H3.3-mutation testing at diagnosis, which should be rapidly integrated into the clinical decision-making algorithm, particularly in atypical DIPG.

Hypofractionation vs conventional radiation therapy for newly diagnosed diffuse intrinsic pontine glioma: a matched-cohort analysis

PURPOSE

Despite conventional radiation therapy, 54 Gy in single doses of 1.8 Gy (54/1.8 Gy) over 6 weeks, most children with diffuse intrinsic pontine glioma (DIPG) will die within 1 year after diagnosis. To reduce patient burden, we investigated the role of hypofractionation radiation therapy given over 3 to 4 weeks. A 1:1 matched-cohort analysis with conventional radiation therapy was performed to assess response and survival.

METHODS AND MATERIALS

Twenty-seven children, aged 3 to 14, were treated according to 1 of 2 hypofractionation regimens over 3 to 4 weeks (39/3 Gy, n=16 or 44.8/2.8 Gy, n=11). All patients had symptoms for ≤3 months, ≥2 signs of the neurologic triad (cranial nerve deficit, ataxia, long tract signs), and characteristic features of DIPG on magnetic resonance imaging. Twenty-seven patients fulfilling the same diagnostic criteria and receiving at least 50/1.8 to 2.0 Gy were eligible for the matched-cohort analysis.

RESULTS

With hypofractionation radiation therapy, the overall survival at 6, 9, and 12 months was 74%, 44%, and 22%, respectively. Progression-free survival at 3, 6, and 9 months was 77%, 43%, and 12%, respectively. Temporary discontinuation of steroids was observed in 21 of 27 (78%) patients. No significant difference in median overall survival (9.0 vs 9.4 months; P=.84) and time to progression (5.0 vs 7.6 months; P=.24) was observed between hypofractionation vs conventional radiation therapy, respectively.

CONCLUSIONS

For patients with newly diagnosed DIPG, a hypofractionation regimen, given over 3 to 4 weeks, offers equal overall survival with less treatment burden compared with a conventional regimen of 6 weeks.