Diffuse intrinsic pontine gliomas: A systematic update on clinical trials and biology

Palliative Care for Children and Adolescents with Non-curative Brain Tumors: A Scoping Review

Children with non-curative brain tumors have a predictable and burdensome neurological decline. Care provision for these children falls in the gap where the acute inpatient services intersect with community-based providers. These children commonly receive care in the community; however, their neurological decline often outpaces engagement with community-based providers. Children with non-curative brain tumors are commonly referred to specialist palliative care services and need timely availability and access to this support. The purpose of this scoping review was to explore the evidence related to standards, guidelines, and models of palliative care provision for children with non-curative brain tumors, and to examine the facilitators and barriers to the implementation of, and access to, these services. Using a narrative synthesis method, a scoping review was conducted according to the Joanna Briggs Institute methodology using six electronic databases (Medline, Embase, Web of Science, Pubmed, CINAHL, and Cochrane Database of Systematic Reviews) from January 2013 to May 2023. A total of 2404 studies were screened for eligibility and 31 were selected for data extraction. There are no international models or standards of care for providing palliative care for children with non-curative brain tumors. Instead, palliative care is delivered at an institutional level, potentially leading to variability in the care that is provided. This variability can threaten the quality of life of these children and their families. Variability in care provision could be minimized by development of standardized palliative care provision. Any proposed standard for palliative care provision for children with non-curative brain tumors should include early integration of palliative care, and allocation of resources to enable training to operationalize referrals to palliative care teams and multidisciplinary care provision across settings, especially home-based care.

Re-Irradiation for the Progressive Pediatric Diffuse Intrinsic Pontine Glioma: A Report on 109 Children From a Single Center

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is a challenging pediatric tumor that frequently progresses within the first year following local radiotherapy. However, several small studies have suggested that re-irradiation may improve quality of life and extend overall survival.

PATIENTS AND METHODS

This retrospective study included 109 children who experienced disease progression ≥3 months after their initial radiotherapy, and subsequently received re-irradiation at a single institution. These patients were compared with a cohort of 60 children, meeting the same criteria, who were treated before adopting the re-irradiation policy and received only the best supportive care (BSC). Most of the re-irradiated children (94%) received first radiation dose as hypofractionation (39 Gy/13 fractions).

RESULTS

The re-irradiation group demonstrated significantly higher overall survival (OS) rates after the first progression, with a 6-month OS of 42% (95% CI: 34%-53%) compared to 16% (95% CI: 8.9%-32%) in the BSC group (p < 0.001). Re-irradiation reduced the hazard of death by more than half (HR = 0.45, p < 0.001). Clinical response (p < 0.001) and radiological response (p = 0.016) were significant predictors of improved survival. While the time from initial radiotherapy to progression (p = 0.059) and higher re-irradiation doses (p = 0.074) were associated with improved OS, these factors did not reach statistical significance but may represent potential prognostic indicators.

CONCLUSION

Re-irradiation improved the OS in children with progression of DIPG and alleviated their signs and symptoms.

Paediatric strategy forum for medicinal product development in diffuse midline gliomas in children and adolescents ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

Fewer than 10 % of children with diffuse midline glioma (DMG) survive 2 years from diagnosis. Radiation therapy remains the cornerstone of treatment and there are no medicinal products with regulatory approval. Although the biology of DMG is better characterized, this has not yet translated into effective treatments. H3K27-alterations initiate the disease but additional drivers are required for malignant growth. Hence, there is an urgent unmet need to develop new multi-modality therapeutic strategies, including alternative methods of drug delivery. ONC201 (DRD2 antagonist and mitochondrial ClpP agonist) is the most widely evaluated investigational drug. Encouraging early data is emerging for CAR T-cells and oncolytic viruses. GD2, B7-H3 and PI3K signalling are ubiquitous targets across all subtypes and therapeutics directed to these targets would potentially benefit the largest number of children. PI3K, ACVR1, MAPK and PDGFRA pathways should be targeted in rational biological combinations. Drug discovery is a very high priority. New specific and potent epigenetic modifiers (PROTACS e.g. SMARCA4 degraders), with blood-brain penetrance are needed. Cancer neuroscience therapeutics are in early development. Overall survival is the preferred regulatory endpoint. However, the evaluation of this can be influenced by the use of re-irradiation at the time of progression. An efficient clinical trial design fit for regulatory purposes for the evaluation of new therapeutics would aid industry and facilitate more efficient therapy development. Challenges in conducting clinical trials such as the need for comparator data and defining endpoints, could be addressed through an international, first-in-child, randomised, complex innovative design trial. To achieve progress: i) drug discovery; ii) new multi-modality, efficient, collaborative, pre-clinical approaches, possibly including artificial intelligence and, iii) efficient clinical trial designs fit for regulatory purposes are required.

PRMT5 inhibition shows in vitro efficacy against H3K27M-altered diffuse midline glioma, but does not extend survival in vivo

H3K27-altered Diffuse Midline Glioma (DMG) is a universally fatal paediatric brainstem tumour. The prevalent driver mutation H3K27M creates a unique epigenetic landscape that may also establish therapeutic vulnerabilities to epigenetic inhibitors. However, while HDAC, EZH2 and BET inhibitors have proven somewhat effective in pre-clinical models, none have translated into clinical benefit due to either poor blood-brain barrier penetration, lack of efficacy or toxicity. Thus, there remains an urgent need for new DMG treatments. Here, we performed wider screening of an epigenetic inhibitor library and identified inhibitors of protein arginine methyltransferases (PRMTs) among the top hits reducing DMG cell viability. Two of the most effective inhibitors, LLY-283 and GSK591, were targeted against PRMT5 using distinct binding mechanisms and reduced the viability of a subset of DMG cells expressing wild-type TP53 and mutant ACVR1. RNA-sequencing and phenotypic analyses revealed that LLY-283 could reduce the viability, clonogenicity and invasion of DMG cells in vitro, representing three clinically important phenotypes, but failed to prolong survival in an orthotopic xenograft model. Together, these data show the challenges of DMG treatment and highlight PRMT5 inhibitors for consideration in future studies of combination treatments.

Phase I trial of panobinostat in children with diffuse intrinsic pontine glioma: A report from the Pediatric Brain Tumor Consortium (PBTC-047)

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is a lethal childhood cancer with median survival of less than 1 year. Panobinostat is an oral multihistone deacetylase inhibitor with preclinical activity in DIPG models. Study objectives were to determine safety, tolerability, maximum tolerated dose (MTD), toxicity profile, and pharmacokinetics of panobinostat in children with DIPG.

PATIENTS AND METHODS

In stratum 1, panobinostat was administered 3 days per week for 3 weeks on, 1 week off to children with progressive DIPG, with dose escalation following a two-stage continual reassessment method. After this MTD was determined, the study was amended to evaluate the MTD in children with nonprogressive DIPG/Diffuse midline glioma (DMG) (stratum 2) on an alternate schedule, 3 days a week every other week in an effort to escalate the dose.

RESULTS

For stratum 1, 19 subjects enrolled with 17/19 evaluable for dose-finding. The MTD was 10 mg/m2/dose. Dose-limiting toxicities included thrombocytopenia and neutropenia. Posterior reversible encephalopathy syndrome was reported in 1 patient. For stratum 2, 34 eligible subjects enrolled with 29/34 evaluable for dose finding. The MTD on this schedule was 22 mg/m2/dose. DLTs included thrombocytopenia, neutropenia, neutropenia with grade 4 thrombocytopenia, prolonged intolerable nausea, and increased ALT.

CONCLUSIONS

The MTD of panobinostat is 10 mg/m2/dose administered 3 times per week for 3 weeks on/1 week off in children with progressive DIPG/DMG and 22 mg/m2/dose administered 3 times per week for 1 week on/1 week off when administered in a similar population preprogression. The most common toxicity for both schedules was myelosuppression.

Advances in Treatment of Diffuse Midline Gliomas

PURPOSE OF REVIEW

Diffuse midline gliomas (DMGs) generally carry a poor prognosis, occur during childhood, and involve midline structures of the central nervous system, including the thalamus, pons, and spinal cord.

RECENT FINDINGS

To date, irradiation has been shown to be the only beneficial treatment for DMG. Various genetic modifications have been shown to play a role in the pathogenesis of this disease. Current treatment strategies span targeting epigenetic dysregulation, cell cycle, specific genetic alterations, and the immune microenvironment. Herein, we review the complex features of this disease as it relates to current and past therapeutic approaches.

Microtubule-Targeting Combined with HDAC Inhibition Is a Novel Therapeutic Strategy for Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine gliomas (DIPG) are an incurable childhood brain cancer for which novel treatments are needed. DIPGs are characterized by a mutation in the H3 histone (H3K27M), resulting in loss of H3K27 methylation and global gene dysregulation. TRX-E-009-1 is a novel anticancer agent with preclinical activity demonstrated against a range of cancers. We examined the antitumor activity of TRX-E-009-1 against DIPG neurosphere cultures and observed tumor-specific activity with IC50s ranging from 20 to 100 nmol/L, whereas no activity was observed against normal human astrocyte cells. TRX-E-009-1 exerted its anti-proliferative effect through the induction of apoptotic pathways, with marked increases in cleaved caspase 3 and cleaved PARP levels, while also restoring histone H3K27me3 methylation. Co-administration of TRX-E-009-1 and the histone deacetylase (HDAC) inhibitor SAHA extended survival in DIPG orthotopic animal models. This antitumor effect was further enhanced with irradiation. Our findings indicate that TRX-E-009-1, combined with HDAC inhibition, represents a novel, potent therapy for children with DIPG.

Rapid Peroxide Removal Limits the Radiosensitization of Diffuse Intrinsic Pontine Glioma (DIPG) Cells by Pharmacologic Ascorbate

Diffuse intrinsic pontine gliomas (DIPG) are an aggressive type of pediatric brain tumor with a very high mortality rate. Surgery has a limited role given the tumor's location. Palliative radiation therapy alleviates symptoms and prolongs survival, but median survival remains less than 1 year. There is no clear role for chemotherapy in DIPGs as trials adding chemotherapy to palliative radiation therapy have failed to improve survival compared to radiation alone. Thus, there is a critical need to identify tissue-specific radiosensitizers to improve clinical outcomes for patients with DIPGs. Pharmacologic (high dose) ascorbate (P-AscH-) is a promising anticancer therapy that sensitizes human tumors, including adult high-grade gliomas, to radiation by acting selectively as a generator of hydrogen peroxide (H2O2) in cancer cells. In this study we demonstrate that in contrast to adult glioma models, P-AscH- does not radiosensitize DIPG. DIPG cells were sensitive to bolus of H2O2 but have faster H2O2 removal rates than GBM models which are radiosensitized by P-AscH-. These data support the hypothesis that P-AscH- does not enhance DIPG radiosensitivity, likely due to a robust capacity to detoxify and remove hydroperoxides.

The Role of Reirradiation in Childhood Progressive Diffuse Intrinsic Pontine Glioma (DIPG): An Ongoing Challenge beyond Radiobiology

To investigate the clinical impact of multiple courses of irradiation on pediatric patients with progressive diffuse intrinsic pontine glioma (DIPG), we conducted a retrospective case series on three children treated at our institution from 2018 to 2022. All children were candidates to receive systemic therapy with vinorelbine and nimotuzumab. Radiotherapy was administered to a total dose of 54 Gy. At any disease progression, our local tumor board evaluated the possibility of offering a new course of radiotherapy. To determine feasibility and assess toxicity rates, all children underwent clinical and hematological evaluation both during and after the treatment. To assess efficacy, all children performed contrast-enhanced MRI almost quarterly after the end of the treatment. In all children, following any treatment course, neurological improvement (>80%) was associated with a radiological response (41.7-46%). The longest overall survival (24 months) was observed in the child who underwent three courses of radiotherapy, without experiencing significant side effects. Even though it goes beyond the understanding of conventional radiobiology, first and second reirradiation in pediatric patients with progressive DIPG may represent a feasible and safe approach, capable of increasing overall survival and disease-free survival in selected patients and improving their quality of life.

Human iPSCs as Model Systems for BMP-Related Rare Diseases

Disturbances in bone morphogenetic protein (BMP) signalling contribute to onset and development of a number of rare genetic diseases, including Fibrodysplasia ossificans progressiva (FOP), Pulmonary arterial hypertension (PAH), and Hereditary haemorrhagic telangiectasia (HHT). After decades of animal research to build a solid foundation in understanding the underlying molecular mechanisms, the progressive implementation of iPSC-based patient-derived models will improve drug development by addressing drug efficacy, specificity, and toxicity in a complex humanized environment. We will review the current state of literature on iPSC-derived model systems in this field, with special emphasis on the access to patient source material and the complications that may come with it. Given the essential role of BMPs during embryonic development and stem cell differentiation, gain- or loss-of-function mutations in the BMP signalling pathway may compromise iPSC generation, maintenance, and differentiation procedures. This review highlights the need for careful optimization of the protocols used. Finally, we will discuss recent developments towards complex in vitro culture models aiming to resemble specific tissue microenvironments with multi-faceted cellular inputs, such as cell mechanics and ECM together with organoids, organ-on-chip, and microfluidic technologies.

Epidemiology, Diagnostic Strategies, and Therapeutic Advances in Diffuse Midline Glioma

Object: Diffuse midline glioma (DMG) is a highly aggressive and lethal brain tumor predominantly affecting children and young adults. Previously known as diffuse intrinsic pontine glioma (DIPG) or grade IV brain stem glioma, DMG has recently been reclassified as "diffuse midline glioma" according to the WHO CNS5 nomenclature, expanding the DMG demographic. Limited therapeutic options result in a poor prognosis, despite advances in diagnosis and treatment. Radiotherapy has historically been the primary treatment modality to improve patient survival. Methods: This systematic literature review aims to comprehensively compile information on the diagnosis and treatment of DMG from 1 January 2012 to 31 July 2023. The review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and utilized databases such as PubMed, Cochrane Library, and SciELO. Results: Currently, molecular classification of DMG plays an increasingly vital role in determining prognosis and treatment options. Emerging therapeutic avenues, including immunomodulatory agents, anti-GD2 CAR T-cell and anti-GD2 CAR-NK therapies, techniques to increase blood-brain barrier permeability, isocitrate dehydrogenase inhibitors, oncolytic and peptide vaccines, are being explored based on the tumor's molecular composition. However, more clinical trials are required to establish solid guidelines for toxicity, dosage, and efficacy. Conclusions: The identification of the H3K27 genetic mutation has led to the reclassification of certain midline tumors, expanding the DMG demographic. The field of DMG research continues to evolve, with encouraging findings that underscore the importance of highly specific and tailored therapeutic strategies to achieve therapeutic success.

The neuropsychological profile of children with Diffuse Intrinsic Pontine Glioma (DIPG) before and after radiation therapy: A prospective longitudinal study

Children with Diffuse Intrinsic Pontine Gliomas (DIPG), a malignant brainstem tumor, experience poor prognosis. Because of the disease's rarity and highly aggressive course, there is a dearth of research on cognitive and psychosocial outcomes in this underserved, vulnerable population. However, evaluating effects of the disease and treatment on the cognitive and daily functioning of these patients is important to better understand their specific needs and improve their quality of life. The current longitudinal study administered prospective neuropsychological assessments to children diagnosed with CNS malignancies, including the largest sample of children with DIPG to date (n = 21, mean age = 7.86 years, range = 3-16) in neurocognitive, behavioral, social-emotional, and adaptive functioning at baseline, two weeks post-radiation, and six months later. The results describe population-based, cross-sectional characteristics and within-patient longitudinal changes. Prior to radiation, children with DIPG exhibited significant weaknesses compared to normative samples in both parent-report and performance-based measures of attention, and tests of processing speed and verbal learning/memory. Younger children demonstrated poorer inhibitory control on performance tests and worse parent-reported behavioral regulation, depression, and social withdrawal compared to older children. Six-months post-radiation, older children exhibited poorer socialization than younger children. Longitudinally, children with DIPG exhibited short-term improvements immediately post-radiation in performance-based attention tests and parent-reported behavior, including attention, hyperactivity, behavioral regulation, and executive function. However, these improvements did not persist and significant decline was documented on tests of attention by six months. Clinical implications for professionals working with children with DIPG and recommendations for cognitive remediation and quality of life interventions are provided.

Deep learning-based prediction of H3K27M alteration in diffuse midline gliomas based on whole-brain MRI

BACKGROUND

H3K27M mutation status significantly affects the prognosis of patients with diffuse midline gliomas (DMGs), but this tumor presents a high risk of pathological acquisition. We aimed to construct a fully automated model for predicting the H3K27M alteration status of DMGs based on deep learning using whole-brain MRI.

METHODS

DMG patients from West China Hospital of Sichuan University (WCHSU; n = 200) and Chengdu Shangjin Nanfu Hospital (CSNH; n = 35) who met the inclusion and exclusion criteria from February 2016 to April 2022 were enrolled as the training and external test sets, respectively. To adapt the model to the human head MRI scene, we use normal human head MR images to pretrain the model. The classification and tumor segmentation tasks are naturally related, so we conducted cotraining for the two tasks to enable information interaction between them and improve the accuracy of the classification task.

RESULTS

The average classification accuracies of our model on the training and external test sets was 90.5% and 85.1%, respectively. Ablation experiments showed that pretraining and cotraining could improve the prediction accuracy and generalization performance of the model. In the training and external test sets, the average areas under the receiver operating characteristic curve (AUROCs) were 94.18% and 87.64%, and the average areas under the precision-recall curve (AUPRC) were 93.26% and 85.4%.

CONCLUSIONS

The developed model achieved excellent performance in predicting the H3K27M alteration status in DMGs, and its good reproducibility and generalization were verified in the external dataset.

Glioblastoma modeling with 3D organoids: progress and challenges

Glioblastoma (GBM) is the most aggressive adult primary brain tumor with nearly universal treatment resistance and recurrence. The mainstay of therapy remains maximal safe surgical resection followed by concurrent radiation therapy and temozolomide chemotherapy. Despite intensive investigation, alternative treatment options, such as immunotherapy or targeted molecular therapy, have yielded limited success to achieve long-term remission. This difficulty is partly due to the lack of pre-clinical models that fully recapitulate the intratumoral and intertumoral heterogeneity of GBM and the complex tumor microenvironment. Recently, GBM 3D organoids originating from resected patient tumors, genetic manipulation of induced pluripotent stem cell (iPSC)-derived brain organoids and bio-printing or fusion with non-malignant tissues have emerged as novel culture systems to portray the biology of GBM. Here, we highlight several methodologies for generating GBM organoids and discuss insights gained using such organoid models compared to classic modeling approaches using cell lines and xenografts. We also outline limitations of current GBM 3D organoids, most notably the difficulty retaining the tumor microenvironment, and discuss current efforts for improvements. Finally, we propose potential applications of organoid models for a deeper mechanistic understanding of GBM and therapeutic development.

Bench-to-bedside investigations of H3 K27-altered diffuse midline glioma: drug targets and potential pharmacotherapies

INTRODUCTION

H3 K27-altered diffuse midline glioma (DMG) is the most common malignant brainstem tumor in the pediatric population. Despite enormous preclinical and clinical efforts, the prognosis remains dismal, with fewer than 10% of patients surviving for two years after diagnosis. Fractionated radiation remains the only standard treatment options for DMG. Developing novel treatments and therapeutic delivery methods is critical to improving outcomes in this devastating disease.

AREAS COVERED

This review addresses recent advances in molecularly targeted pharmacotherapy and immunotherapy in DMG. The clinical presentation, diagnostic workup, unique pathological challenges, and current clinical trials are highlighted throughout.

EXPERT OPINION

Promising pharmacotherapies targeting various components of DMG pathology and the application of immunotherapies have the potential to improve patient outcomes. However, novel approaches are needed to truly revolutionize treatment for this tumor. First, combinational therapy should be employed, as DMG can develop resistance to single-agent approaches and many therapies are susceptible to rapid clearance from the brain. Second, drug-tumor residence time, i.e. the time for which a therapeutic is present at efficacious concentrations within the tumor, must be maximized to facilitate a durable treatment response. Engineering extended drug delivery methods with minimal off-tumor toxicity should be a focus of future studies.

Engineered extracellular vesicles (EVs): Promising diagnostic/therapeutic tools for pediatric high-grade glioma

Diffuse intrinsic pontine glioma (DIPG) is a highly malignant brain tumor that mainly occurs in children with extremely low overall survival. Traditional therapeutic strategies, such as surgical resection and chemotherapy, are not feasible mostly due to the special location and highly diffused features. Radiotherapy turns out to be the standard treatment method but with limited benefits of overall survival. A broad search for novel and targeted therapies is in the progress of both preclinical investigations and clinical trials. Extracellular vesicles (EVs) emerged as a promising diagnostic and therapeutic candidate due to their distinct biocompatibility, excellent cargo-loading-delivery capacity, high biological barrier penetration efficiency, and ease of modification. The utilization of EVs in various diseases as biomarker diagnoses or therapeutic agents is revolutionizing modern medical research and practice. In this review, we will briefly talk about the research development of DIPG, and present a detailed description of EVs in medical applications, with a discussion on the application of engineered peptides on EVs. The possibility of applying EVs as a diagnostic tool and drug delivery system in DIPG is also discussed.

Radiotherapy for Diffuse Intrinsic Pontine Glioma: Insufficient but Indispensable

Diffuse intrinsic pontine gliomas (DIPGs) account for 10%-20% of all central nervous system tumors in children and are the leading cause of death in children with brain tumors. Although many clinical trials have been conducted over the past decades, the survival outcome has remained unchanged. Over 90% of children die within 2 years of the diagnosis, and radiotherapy remains the standard treatment to date. To improve the prognosis, hyperfractionated and hypofractionated radiotherapy and/or addition of radiosensitizers have been investigated. However, none of the radiotherapy approaches have shown a survival benefit, and the overall survival of patients with DIPG is approximately 11 months. Here, we comprehensively review the management of DIPG with focus on radiotherapy.

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.

11C-methionine PET imaging characteristics in children with diffuse intrinsic pontine gliomas and relationship to survival and H3 K27M mutation status

PURPOSE

This study aimed to describe ¹¹C-methionine (¹¹C-MET) PET imaging characteristics in patients with paediatric diffuse intrinsic pontine glioma (DIPG) and correlate them with survival and H3 K27M mutation status.

METHODS

We retrospectively analysed 98 children newly diagnosed with DIPG who underwent ¹¹C-MET PET. PET imaging characteristics evaluated included uptake intensity, uniformity, metabolic tumour volume (MTV), and total lesion methionine uptake (TLMU). The maximum, mean, and peak of the tumour-to-background ratio (TBR), calculated as the corresponding standardised uptake values (SUV) divided by the mean reference value, were also recorded. The associations between the PET imaging characteristics and clinical outcomes in terms of progression-free survival (PFS) and overall survival (OS) and H3 K27M mutation status were assessed, respectively.

RESULTS

In univariate analysis, imaging characteristics significantly associated with shorter PFS and OS included a higher uniformity grade, higher TBRs, larger MTV, and higher TLMU. In multivariate analysis, larger MTV at diagnosis, shorter symptom duration, and no treatment were significantly correlated with shorter PFS and OS. The PET imaging features were not correlated with H3 K27M mutation status.

CONCLUSION

Although several imaging features were significantly associated with PFS and OS, only MTV, indicating the size of the active tumour, was identified as a strong independent prognostic factor.

Advances and Clinical Trials Update in the Treatment of Diffuse Intrinsic Pontine Gliomas

BACKGROUND

Diffuse intrinsic pontine gliomas (DIPGs) are high-grade gliomas (HGGs) that occur primarily in children, and represent a leading cause of death in pediatric patients with brain tumors with a median overall survival of only 8-11 months.

SUMMARY

While these lesions were previously thought to behave similarly to adult HGG, emerging data have demonstrated that DIPG is a biologically distinct entity from adult HGG frequently driven by mutations in the histone genes H3.3 and H3.1 not found in adult glioma. While biopsy of DIPG was historically felt to confer unacceptable risk of morbidity and mortality, multiple studies have demonstrated that stereotactic biopsy of DIPG is safe, allowing not only for improved understanding of DIPG but also forming the basis for protocols for personalized medicine in DIPG. However, current options for personalized medicine in DIPG are limited by the lack of efficacious targeted therapies for the mutations commonly found in DIPG. Multiple treatment modalities including targeted therapies, immunotherapy, convection-enhanced delivery, and focused ultrasound are in various stages of investigation.

KEY MESSAGE

Increasing frequency of biopsy for DIPG has identified distinct driving mutations that may serve as therapeutic targets. Novel treatment modalities are under investigation.

Role of neuronavigation in the surgical management of brainstem gliomas

Objective

NeuroNavigation (NN) is a widely used intraoperative imaging guidance technique in neurosurgical operations; however, its value in brainstem glioma (BSG) surgery is inadequately reported and lacks objective proof. This study aims to investigate the applicational value of NN in BSG surgery.

Method

A retrospective analysis was performed on 155 patients with brainstem gliomas who received craniotomy from May 2019 to January 2022 at Beijing Tiantan Hospital. Eighty-four (54.2%) patients received surgery with NN. Preoperative and postoperative cranial nerve dysfunctions, muscle strength, and Karnofsky (KPS) were evaluated. Patients' radiological features, tumor volume, and extent of resection (EOR) were obtained from conventional MRI data. Patients' follow-up data were also collected. Comparative analyses on these variables were made between the NN group and the non-NN group.

Result

The usage of NN is independently related to a higher EOR in diffuse intrinsic pontine glioma (DIPG) (p=0.005) and non-DIPG group (p<0.001). It was observed that fewer patients in the NN group suffered from deterioration of KPS (p=0.032) and cranial nerve function (p=0.017) in non-DIPG group, and deterioration of muscle strength (p=0.040) and cranial nerve function (p=0.038) in DIPG group. Moreover, the usage of NN is an independent protective factor for the deterioration of KPS (p=0.04) and cranial nerve function (p=0.026) in non-DIPG patients and the deterioration of muscle strength (p=0.009) in DIPG patients. Furthermore, higher EOR subgroups were found to be independently related to better prognoses in DIPG patients (p=0.008).

Conclusion

NN has significant value in BSG surgery. With the assistance of NN, BSG surgery achieved higher EOR without deteriorating patients' functions. In addition, DIPG patients may benefit from the appropriate increase of EOR.

Immunotherapy for Pediatric Brain and Spine Tumors: Current State and Future Directions

BACKGROUND

Brain tumors are the most common solid tumors and the leading cause of cancer-related deaths in children. Incidence in the USA has been on the rise for the last 2 decades. While therapeutic advances in diagnosis and treatment have improved survival and quality of life in many children, prognosis remains poor and current treatments have significant long-term sequelae.

SUMMARY

There is a substantial need for the development of new therapeutic approaches, and since the introduction of immunotherapy by immune checkpoint inhibitors, there has been an exponential increase in clinical trials to adopt these and other immunotherapy approaches in children with brain tumors. In this review, we summarize the current immunotherapy landscape for various pediatric brain tumor types including choroid plexus tumors, embryonal tumors (medulloblastoma, AT/RT, PNETs), ependymoma, germ cell tumors, gliomas, glioneuronal and neuronal tumors, and mesenchymal tumors. We discuss the latest clinical trials and noteworthy preclinical studies to treat these pediatric brain tumors using checkpoint inhibitors, cellular therapies (CAR-T, NK, T cell), oncolytic virotherapy, radioimmunotherapy, tumor vaccines, immunomodulators, and other targeted therapies.

KEY MESSAGES

The current landscape for immunotherapy in pediatric brain tumors is still emerging, but results in certain tumors have been promising. In the age of targeted therapy, genetic tumor profiling, and many ongoing clinical trials, immunotherapy will likely become an increasingly effective tool in the neuro-oncologist armamentarium.

MRI comparative study of diffuse midline glioma, H3 K27-altered and glioma in the midline without H3 K27-altered

PURPOSE

The MRI features of Diffuse midline glioma, H3 K27-altered and glioma in the midline without H3 K27-altered were compared and analyzed, and the changes in the apparent diffusion coefficient (ADC) of the two groups were quantitatively analyzed.

METHODS

The MRI images of 35 patients with Diffuse midline gliomas, H3 K27-altered and gliomas in the midline without H3 K27-altered were analyzed retrospectively. The location, edge, signal, peritumoral edema and enhancement characteristics of the lesions were observed, and the changes in ADC values were analyzed.

RESULTS

In the H3 K27-altered group, 85.7% (12/14) of the tumors were located in the thalamus and brainstem compared with 28.6% (6/21) in the no H3 K27-altered group. In the H3 K27-altered group, for tumors only located in the midline area, only 14.3% (1/7) had irregular shapes and unclear boundaries, while for tumors also invaded the extramidline tissues 85.7% (6/7) had irregular shapes and unclear boundaries.The"basilar artery wrapped sign" was found in 6 patients with tumors located in the pons in the H3 K27-altered group, but none in the no H3 K27-altered group had this sign. In the H3 K27-altered group, only 14.3% (1/7) of the tumors confined to the midline area had small cystic degeneration and necrosis, while for tumors also invaded the extramidline tissues, 100% (7/7) of the tumors had cystic degeneration and necrosis, and the cystic degeneration and necrosis only located in the extramidline region of the tumor in 6 cases.A total of 78.6% (11/14) of tumors in the H3 K27-altered group showed mild to moderate enhancement, while 47.6% (10/21) of tumors in the no H3 K27-altered group showed mild to moderate enhancement. The average peritumoral edema index was 1.13 in the H3 K27-altered group and 1.75 in the no H3 K27-altered group. The average ADC value of tumor in the H3 K27-altered group was 7.83 × 10^- 4 mm²/s, and the ratio to normal brain tissue was 0.844, while the values in the no H3 K27-altered group were 13.5 × 10^- 4 mm²/s and 1.75, respectively.

CONCLUSION

Compared with gliomas in the midline without H3 K27-altered, The MRI findings and ADC value of Diffuse midline gliomas, H3K27-altered have some characteristics, which can help improve the diagnosis and differential diagnosis.

Targeted therapy for pediatric diffuse intrinsic pontine glioma: a single-center experience

Background:

Diffuse intrinsic pontine glioma (DIPG) is a fatal disease with a median overall survival (OS) of less than 12 months after diagnosis. Radiotherapy (RT) still remains the mainstay treatment. Several other therapeutic strategies have been attempted in the last years without a significant effect on OS. Although radiological imaging is the gold standard for DIPG diagnosis, the urgent need to improve the survival has led to the reconsideration of biopsy with the aim to better understand the molecular profile of DIPG and support personalized treatment.

Methods:

In this study, we present a single-center experience in treating DIPG patients at disease progression combining targeted therapies with standard of care. Biopsy was proposed to all patients at diagnosis or disease progression. First-line treatment included RT and nimotuzumab/vinorelbine or temozolomide. Immunohistochemistry-targeted research included study of mTOR/p-mTOR pathway and BRAFv600E. Molecular analyses included polymerase chain reaction, followed by Sanger sequences and/or next-generation sequencing.

Results:

Based on the molecular profile, targeted therapy was administered in 9 out of 25 patients, while the remaining 16 patients were treated with standard of care. Personalized treatment included inhibition of the PI3K/AKT/mTOR pathway (5/9), PI3K/AKT/mTOR pathway and BRAFv600E (1/9), ACVR1 (2/9) and PDGFRA (1/9); no severe side effects were reported during treatment. Response to treatment was evaluated according to Response Assessment in Pediatric Neuro-Oncology criteria, and the overall response rate within the cohort was 66%. Patients treated with targeted therapies were compared with the control cohort of 16 patients. Clinical and pathological characteristics of the two cohorts were homogeneous. Median OS in the personalized treatment and control cohort was 20.26 and 14.18 months, respectively (p = 0.032). In our experience, the treatment associated with the best OS was everolimus.

Conclusion:

Despite the small simple size of our study, our data suggest a prognostic advantage and a safe profile of targeted therapies in DIPG patients, and we strongly advocate to reconsider the role of biopsy for these patients.

A microRNA Prognostic Signature in Patients with Diffuse Intrinsic Pontine Gliomas through Non-Invasive Liquid Biopsy

Simple Summary

Diffuse intrinsic pontine glioma (DIPG) is a neuro-radiologically defined tumor of the brainstem, primarily affecting children, with most diagnoses occurring between 5 and 7 years of age. Surgical removal in DIPGs is not feasible. Subsequent tumor progression is almost universal and no biomarker for predicting the course of the disease has entered into clinical practice so far. Under these premises, it is essential to develop reliable biomarkers that are able to improve outcomes and stratify patients using non-invasive methods to determine tumor profiles. We designed a study assessing circulating miRNA expression by a high-throughput platform and divided patients into training and validation phases in order to disclose a potential signature with clinical impact. Our results for the first time have proved the usefulness of blood-circulating nucleic acids as powerful, easy-to-assay molecular markers of disease status in DIPG.

Abstract

Diffuse midline gliomas (DMGs) originate in the thalamus, brainstem, cerebellum and spine. This entity includes tumors that infiltrate the pons, called diffuse intrinsic pontine gliomas (DIPGs), with a rapid onset and devastating neurological symptoms. Since surgical removal in DIPGs is not feasible, the purpose of this study was to profile circulating miRNA expression in DIPG patients in an effort to identify a non-invasive prognostic signature with clinical impact. Using a high-throughput platform, miRNA expression was profiled in serum samples collected at the time of MRI diagnosis and prior to radiation and/or systemic therapy from 47 patients enrolled in clinical studies, combining nimotuzumab and vinorelbine with concomitant radiation. With progression-free survival as the primary endpoint, a semi-supervised learning approach was used to identify a signature that was also tested taking overall survival as the clinical endpoint. A signature comprising 13 circulating miRNAs was identified in the training set (n = 23) as being able to stratify patients by risk of disease progression (log-rank p = 0.00014; HR = 7.99, 95% CI 2.38–26.87). When challenged in a separate validation set (n = 24), it confirmed its ability to predict progression (log-rank p = 0.00026; HR = 5.51, 95% CI 2.03–14.9). The value of our signature was also confirmed when overall survival was considered (log-rank p = 0.0021, HR = 4.12, 95% CI 1.57–10.8). We have identified and validated a prognostic marker based on the expression of 13 circulating miRNAs that can shed light on a patient’s risk of progression. This is the first demonstration of the usefulness of nucleic acids circulating in the blood as powerful, easy-to-assay molecular markers of disease status in DIPG. This study provides Class II evidence that a signature based on 13 circulating miRNAs is associated with the risk of disease progression.

Compassionate use of Quantum Magnetic Resonance Therapy for treatment of children with Diffuse Brainstem Glioma in Mexico City: a single institutional experience

PURPOSE

Diffuse Brainstem Glioma (DBG) is a catastrophic brain tumor with a survival rate of less than 10% two years after diagnosis despite the existence of different treatment protocols. Among the devices that use magnetic fields generated by Magnetic Resonance Imaging is Quantum Magnetic Resonance Therapy (QMRT).

METHODS

Five children diagnosed with DBG in our institution in Mexico City underwent treatment of compassionate use with QMRT between December 2018 and July 2019. A survival analysis was performed with previously reported historical data (n = 15).

RESULTS

Two patients (40%) survived after three years of follow-up; the log-rank test showed a statistically significant difference in overall survival between both groups (p = 0.032). All patients tolerated the treatment adequately without reporting any severe clinical or neuroradiological adverse effects. Of the patients included, all showed a decrease in the tumor one month after the end of the treatment, although there was great variability in the response and the difference was not statistically significant (p = 0.06).

CONCLUSIONS

Although future investigations are needed to confirm the findings reported in the present study, the improvement in survival is promising for a group of patients whose prognosis has been catastrophic over the years. Trial registration NCT03577600.

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.

Palliative and end-of-life symptoms management for children with diffuse intrinsic pontine glioma

Background: This study aimed to investigate diffuse intrinsic pontine glioma-specific symptoms in the last 12 weeks before death and to describe current palliative care. Materials & methods: A retrospective study included 80 pediatric diffuse intrinsic pontine glioma patients diagnosed between January 2018 and December 2019. Results: The most frequently encountered symptoms were headache, gait disturbance, vomiting, dysphagia, sensory loss, seizures and constipation. Steroids were used in 96% of patients with a high success rate, as well as analgesics (67.5%), antiemetics (59%), neuropathic medication (42.5%) and anticonvulsants (37.5%). Re-irradiation improved symptoms in 50% of patients. Conclusion: Steroids were efficient in managing many symptoms, with tolerated side effects. The symptomatic treatment succeeded in relieving end-of-life symptoms. Re-irradiation should be considered a good palliative tool in addition to regular symptomatic treatment.

Chorioallantoic membrane (CAM) assay to study treatment effects in diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is a lethal pediatric brain tumor. While there are a number of in vivo rodent models for evaluating tumor biology and response to therapy, these models require significant time and resources. Here, we established the chick-embryo chorioallantoic (CAM) assay as an affordable and time efficient xenograft model for testing a variety of treatment approaches for DIPG. We found that patient-derived DIPG tumors develop in the CAM and maintain the same genetic and epigenetic characteristics of native DIPG tumors. We monitored tumor response to pharmaco- and radiation therapy by 3-D ultrasound volumetric and vasculature analysis. In this study, we established and validated the CAM model as a potential intermediate xenograft model for DIPG and its use for testing novel treatment approaches that include pharmacotherapy or radiation.

Stereotactic Biopsy for Brainstem Lesions: A Meta-analysis with Noncomparative Binary Data

Objectives

To evaluate the diagnostic yield and safety of brainstem stereotactic biopsy for brainstem lesions.

Methods

We performed a meta-analysis of English articles retrieved from the PubMed, Web of Science, Cochrane Library, and APA psycInfo databases up to May 12, 2021. A binary fixed-effect model, the inverse variance method, or a binary random-effect model, the Dersimonian Laird method, were utilized for pooling the data. This meta-analysis was registered with INPLASY, INPLASY202190034.

Findings

A total of 41 eligible studies with 2792 participants were included. The weighted average diagnostic yield was 97.0% (95% confidential interval [CI], 96.0-97.9%). The weighted average proportions of temporary complications, permanent deficits, and deaths were 6.2% (95% CI, 4.5–7.9%), .5% (95% CI, .2–.8%), and .3% (95% CI, .1–.5%), respectively. The subgroup analysis indicated a nearly identical weighted average diagnostic yield between MRI-guided stereotactic biopsy and CT-guided stereotactic biopsy (95.9% vs 95.8%) but slightly increased proportions of temporary complications (7.9% vs 6.0%), permanent deficits (1.9% vs .2%), and deaths (1.1% vs .4%) in the former compared to the latter. Moreover, a greater weighted average diagnostic yield (99.2% vs 97.6%) and lower proportions of temporary complications (5.1% vs 6.8%) and deaths (.7% vs 1.5%) were shown in the pediatric patient population than in the adult patient population.

Conclusions

Brainstem stereotactic biopsy demonstrates striking accuracy plus satisfying safety in the diagnosis of brainstem lesions. The diagnostic yield, morbidity, and mortality mildly vary based on the diversity of assistant techniques and subject populations.

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 brainstem tumors in children. Tumor biology and hope for a better outcome. Current state of the problem]

Diffuse brainstem tumor is a fatal disease and the main cause of child mortality from neoplasms of central nervous system. So far, no effective therapy has been found for this disease. The authors discuss the modern aspects of clinical data, biology, diagnosis and treatment of patients with diffuse brainstem tumors.

Retrospective study of diffuse intrinsic pontine glioma in the Belgian population: a 25 year experience

INTRODUCTION

Diffuse intrinsic pontine glioma is a rare disease with a high mortality. Our primary aim was to determine the incidence of this disease in Belgium. Secondly, we wanted to compare the treatment approach of Belgian pediatric oncology centres, to investigate possibilities for improvement.

METHODS

We retrospectively collected and analysed data on DIPG-patients diagnosed between 1994 and 2018 and recorded in the Belgian Cancer Registry. We included patients ≤ 18 years who were followed in one of the eight Belgian pediatric oncology centres.

RESULTS

We included 100 patients. Files were complete in 87 patients. We observed an increase in diagnoses with an incidence of 3.1 per 1,000,000 persons (aged 0-≤ 18) per year over the last 5 years compared to an overall incidence of 1.8. Biopsy was performed at diagnosis in 51.7% of patients. In one fifth this was study-related. Mutation analysis was known in eight patients, of which six showed the H3 K27M-mutation. 58.8% of patients received chemotherapy, without a significant survival benefit. 12.6% of patients were included in a clinical trial. Biopsy rate and the use of chemotherapy differed widely between centres. Mean OS and PFS were 10.49 and 4.87 months respectively. We observed an improved survival over time.

CONCLUSIONS

Over the past 25 years, we observed an increase of new DIPG-diagnoses. Outcome in our cohort is comparable with literature findings. We demonstrate an important heterogeneity in treatment approach between different centres and limited inclusion in clinical trials. Therefore, collaboration between centres and inclusion of patients in clinical trials is much needed.

A phase I/II study of veliparib (ABT-888) with radiation and temozolomide in newly diagnosed diffuse pontine glioma: a Pediatric Brain Tumor Consortium study

BACKGROUND

A Pediatric Brain Tumor Consortium (PBTC) phase I/II trial of veliparib and radiation followed by veliparib and temozolomide (TMZ) was conducted in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG). The objectives were to: (i) estimate the recommended phase II dose (RP2D) of veliparib with concurrent radiation; (ii) evaluate the pharmacokinetic parameters of veliparib during radiation; (iii) evaluate feasibility of intrapatient TMZ dose escalation; (iv) describe toxicities of protocol therapy; and (v) estimate the overall survival distribution compared with historical series.

METHODS

Veliparib was given Monday through Friday b.i.d. during radiation followed by a 4-week rest. Patients then received veliparib at 25 mg/m2 b.i.d. and TMZ 135 mg/m2 daily for 5 days every 28 days. Intrapatient dose escalation of TMZ was investigated for patients experiencing minimal toxicity.

RESULTS

Sixty-six patients (65 eligible) were enrolled. The RP2D of veliparib was 65 mg/m2 b.i.d. with radiation. Dose-limiting toxicities during radiation with veliparib therapy included: grade 2 intratumoral hemorrhage (n = 1), grade 3 maculopapular rash (n = 2), and grade 3 nervous system disorder (generalized neurologic deterioration) (n = 1). Intrapatient TMZ dose escalation during maintenance was not tolerated. Following a planned interim analysis, it was concluded that this treatment did not show a survival benefit compared with PBTC historical controls, and accrual was stopped for futility. The 1- and 2-year overall survival rates were 37.2% (SE 7%) and 5.3% (SE 3%), respectively.

CONCLUSION

Addition of veliparib to radiation followed by TMZ and veliparib was tolerated but did not improve survival for patients with newly diagnosed DIPG.

TRIAL REGISTRATION

NCT01514201.

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.

Advanced Spheroid, Tumouroid and 3D Bioprinted In-Vitro Models of Adult and Paediatric Glioblastoma

The life expectancy of patients with high-grade glioma (HGG) has not improved in decades. One of the crucial tools to enable future improvement is advanced models that faithfully recapitulate the tumour microenvironment; they can be used for high-throughput screening that in future may enable accurate personalised drug screens. Currently, advanced models are crucial for identifying and understanding potential new targets, assessing new chemotherapeutic compounds or other treatment modalities. Recently, various methodologies have come into use that have allowed the validation of complex models—namely, spheroids, tumouroids, hydrogel-embedded cultures (matrix-supported) and advanced bioengineered cultures assembled with bioprinting and microfluidics. This review is designed to present the state of advanced models of HGG, whilst focusing as much as is possible on the paediatric form of the disease. The reality remains, however, that paediatric HGG (pHGG) models are years behind those of adult HGG. Our goal is to bring this to light in the hope that pGBM models can be improved upon.

Mesenchymal Stem Cells Successfully Deliver Oncolytic Virotherapy to Diffuse Intrinsic Pontine Glioma

PURPOSE

Diffuse intrinsic pontine glioma (DIPG) is among the deadliest of pediatric brain tumors. Radiotherapy is the standard-of-care treatment for DIPG, but offers only transient relief of symptoms for patients with DIPG without providing significant survival benefit. Oncolytic virotherapy is an anticancer treatment that has been investigated for treating various types of brain tumors.

EXPERIMENTAL DESIGN

Here, we have explored the use of mesenchymal stem cells (MSC) for oncolytic virus (OV) delivery and evaluated treatment efficacy using preclinical models of DIPG. The survivin promoter drives the conditional replication of OV used in our studies. The efficiency of OV entry into the cells is mediated by fiber modification with seven lysine residues (CRAd.S.pK7). Patients' samples and cell lines were analyzed for the expression of viral entry proteins and survivin. The ability of MSCs to deliver OV to DIPG was studied in the context of a low dose of irradiation.

RESULTS

Our results show that DIPG cells and tumors exhibit robust expression of cell surface proteins and survivin that enable efficient OV entry and replication in DIPG cells. MSCs loaded with OV disseminate within a tumor and release OV throughout the DIPG brainstem xenografts in mice. Administration of OV-loaded MSCs with radiotherapy to mice bearing brainstem DIPG xenografts results in more prolonged survival relative to that conferred by either therapy alone (P < 0.01).

CONCLUSIONS

Our study supports OV, CRAd.S.pK7, encapsulated within MSCs as a therapeutic strategy that merits further investigation and potential translation for DIPG treatment.

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.

Dual targeting of polyamine synthesis and uptake in diffuse intrinsic pontine gliomas

Diffuse intrinsic pontine glioma (DIPG) is an incurable malignant childhood brain tumor, with no active systemic therapies and a 5-year survival of less than 1%. Polyamines are small organic polycations that are essential for DNA replication, translation and cell proliferation. Ornithine decarboxylase 1 (ODC1), the rate-limiting enzyme in polyamine synthesis, is irreversibly inhibited by difluoromethylornithine (DFMO). Herein we show that polyamine synthesis is upregulated in DIPG, leading to sensitivity to DFMO. DIPG cells compensate for ODC1 inhibition by upregulation of the polyamine transporter SLC3A2. Treatment with the polyamine transporter inhibitor AMXT 1501 reduces uptake of polyamines in DIPG cells, and co-administration of AMXT 1501 and DFMO leads to potent in vitro activity, and significant extension of survival in three aggressive DIPG orthotopic animal models. Collectively, these results demonstrate the potential of dual targeting of polyamine synthesis and uptake as a therapeutic strategy for incurable DIPG.

Exploiting Gangliosides for the Therapy of Ewing's Sarcoma and H3K27M-Mutant Diffuse Midline Glioma

Simple Summary

Osteosarcoma, Ewing’s sarcoma, and H3K27M-mutant diffuse midline glioma are rare but aggressive malignancies occurring mainly in children. Due to their rareness and often fatal course, drug development is challenging. Here, we repurposed the existing drugs dinutuximab and eliglustat and investigated their potential to directly target or indirectly modulate the tumor cell-specific ganglioside GD2. Our data suggest that targeting and/or modulating tumor cell-specific GD2 may offer a new therapeutic strategy for the above mentioned tumor entities.

Abstract

The ganglioside GD2 is an important target in childhood cancer. Nevertheless, the only therapy targeting GD2 that is approved to date is the monoclonal antibody dinutuximab, which is used in the therapy of neuroblastoma. The relevance of GD2 as a target in other tumor entities remains to be elucidated. Here, we analyzed the expression of GD2 in different pediatric tumor entities by flow cytometry and tested two approaches for targeting GD2. H3K27M-mutant diffuse midline glioma (H3K27M-mutant DMG) samples showed the highest expression of GD2 with all cells strongly positive for the antigen. Ewing’s sarcoma (ES) samples also showed high expression, but displayed intra- and intertumor heterogeneity. Osteosarcoma had low to intermediate expression with a high percentage of GD2-negative cells. Dinutuximab beta in combination with irinotecan and temozolomide was used to treat a five-year-old girl with refractory ES. Disease control lasted over 12 months until a single partially GD2-negative intracranial metastasis was detected. In order to target GD2 in H3K27M-mutant DMG, we blocked ganglioside synthesis via eliglustat, since dinutuximab cannot cross the blood–brain barrier. Eliglustat is an inhibitor of glucosylceramide synthase, and it is used for treating children with Gaucher’s disease. Eliglustat completely inhibited the proliferation of primary H3K27M-mutant DMG cells in vitro. In summary, our data provide evidence that dinutuximab might be effective in tumors with high GD2 expression. Moreover, disrupting the ganglioside metabolism in H3K27M-mutant DMG could open up a new therapeutic option for this highly fatal cancer.

Tumor genotype dictates radiosensitization after Atm deletion in primary brainstem glioma models

Diffuse intrinsic pontine glioma (DIPG) kills more children than any other type of brain tumor. Despite clinical trials testing many chemotherapeutic agents, palliative radiotherapy remains the standard treatment. Here, we utilized Cre/loxP technology to show that deleting Ataxia telangiectasia mutated (Atm) in primary mouse models of DIPG can enhance tumor radiosensitivity. Genetic deletion of Atm improved survival of mice with p53-deficient but not p53 wild-type gliomas after radiotherapy. Similar to patients with DIPG, mice with p53 wild-type tumors had improved survival after radiotherapy independent of Atm deletion. Primary p53 wild-type tumor cell lines induced proapoptotic genes after radiation and repressed the NRF2 target, NAD(P)H quinone dehydrogenase 1 (Nqo1). Tumors lacking p53 and Ink4a/Arf expressed the highest level of Nqo1 and were most resistant to radiation, but deletion of Atm enhanced the radiation response. These results suggest that tumor genotype may determine whether inhibition of ATM during radiotherapy will be an effective clinical approach to treat DIPGs.

Parents' experiences of postmortem tumor donation for high-grade gliomas: benefits and suggested improvements

BACKGROUND

Pediatric high-grade glioma is a devastating diagnosis. There has been no improvement in outcomes for several decades, with few children surviving 2 years postdiagnosis. Research progress has been hampered by a lack of tumor samples, which can be used to develop and test novel therapies. Postmortem tumor donations are therefore a valuable opportunity to collect tissue. In this study, we explored Australian parents' experiences of donating their child's tumor for research after their child had died.

METHODS

We collected qualitative data from 11 bereaved parents who consented to donate samples of their child's high-grade glioma for research postmortem. We asked parents about their perceived benefits/burdens of the autopsy, recommendations for improving consent discussions, and decision regret.

RESULTS

Parents hoped that their donation would help to find a cure for future children with high-grade glioma. They described feeling comforted knowing that their child's suffering may help others. Some parents also felt that the donation would help them better understand their child's tumor. Although some parents described discomfort about procedures leading up to the autopsy, parents reported minimal regret regarding their decision to donate their child's tumor. Parents provided recommendations to improve consent discussions, such as providing more information about the autopsy logistics and why the donation was needed.

CONCLUSION

Parents consented to autopsy for altruistic reasons, although donation may also assist parents in their grieving. There is a strong need to improve access to tumor donations for any family who wishes to donate.

Diffuse Intrinsic Pontine Glioma (DIPG): Breakthrough and Clinical Perspective

Diffuse intrinsic pontine glioma (DIPG) mainly affects children with a median age of 6-7 years old. It accounts for 10% of all pediatric tumors. Unfortunately, DIPG has a poor prognosis, and the median survival is generally less than 16-24 months independently from the treatment received. Up to now, children with DIPG are treated with focal radiotherapy alone or in combination with antitumor agents. In the last decade, ONC201 known as dopamine receptor antagonist was uncovered, by a high throughput screening of public libraries of compounds, to be endowed with cytotoxic activity against several cancer cell lines. Efforts were made to identify the real ONC201 target, responsible for its antiproliferative effect. The hypothesized targets were the Tumor necrosis factor-Related Apoptosis-Inducing Ligand stimulation (TRAIL), two oncogenic kinases (ERK/AKT system) that target the same tumor-suppressor gene (FOXO3a), dopamine receptors (DRD2 and DRD3 subtypes) and finally the mitochondrial Caseynolitic Protease P (ClpP). ONC201 structure-activity relationship is extensively discussed in this review, together with other two classes of compounds, namely ADEPs and D9, already known for their antibiotic activity but noteworthy to be discussed and studied as potential "leads" for the development of new drugs to be used in the treatment of DIPG. In this review, a detailed and critical description of ONC201, ADEPs, and D9 pro-apoptotic activity is made, with particular attention to the specific interactions established with its targets that also are intimately described. Pubmed published patents and clinical trial reports of the last ten years were used as the bibliographic source.

Canadian Pediatric Neuro-Oncology Standards of Practice

Primary CNS tumors are the leading cause of cancer-related death in pediatrics. It is essential to understand treatment trends to interpret national survival data. In Canada, children with CNS tumors are treated at one of 16 tertiary care centers. We surveyed pediatric neuro-oncologists to create a national standard of practice to be used in the absence of a clinical trial for seven of the most prevalent brain tumors in children. This allowed description of practice across the country, along with a consensus. This had a multitude of benefits, including understanding practice patterns, allowing for a basis to compare in future research and informing Health Canada of the current management of patients. This also allows all children in Canada to receive equivalent care, regardless of location.

OKlahoma Nitrone-007: novel treatment for diffuse intrinsic pontine glioma

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is the most common brainstem cancer in childhood. This rapidly progressing brainstem glioma holds a very dismal prognosis with median survival of less than 1 year. Despite extensive research, no significant therapeutic advancements have been made to improve overall survival in DIPG patients.

METHODS

Here, we used an orthotopic xenograft pediatric DIPG (HSJD-DIPG-007) mouse model to monitor the effects of anti-cancer agent, OKlahoma Nitrone-007 (OKN-007), as an inhibitor of tumor growth after 28 days of treatment. Using magnetic resonance imaging (MRI), we confirmed the previously described efficacy of LDN-193189, a known activin A receptor, type I (ACVR1) inhibitor, in decreasing tumor burden and found that OKN-007 was equally efficacious.

RESULTS

After 28 days of treatment, the tumor volumes were significantly decreased in OKN-007 treated mice (p < 0.01). The apparent diffusion coefficient (ADC), as a measure of tissue structural alterations, was significantly decreased in OKN-007 treated tumor-bearing mice (p < 0.0001). Histological analysis also showed a significant decrease in CD34 expression, essential for angiogenesis, of OKN-007 treated mice (p < 0.05) compared to LDN-193189 treated mice. OKN-007-treated mice also significantly decreased protein expression of the human nuclear antigen (HNA) (p < 0.001), ACVR1 (p < 0.0001), and c-MET (p < 0.05), as well as significantly increased expression of cleaved caspase 3 (p < 0.001) and histone H3 K27-trimethylation (p < 0.01), compared to untreated mouse tumors.

CONCLUSIONS

With the dismal prognosis and limited effective chemotherapy available for DIPG, there is significant room for continued research studies, and OKN-007 merits further exploration as a therapeutic agent.

Retrospective analysis of the clinical and radiological features of 94 consecutive DIPGs patients to investigate the factors determining the development of hydrocephalus and its impact on clinical status and survival

PURPOSE

There is no consensus in the literature about the impact of hydrocephalus on clinical course and overall survival of diffuse intrinsic pontine gliomas (DIPG) patients as well as about its specific treatment. Authors reviewed a series of DIPG patients to investigate factors related to the onset of hydrocephalus, its treatment, and its impact on clinical course and prognosis.

METHODS

A retrospective observational study was performed enrolling pediatric patients affected by DIPG from 2008 to 2018. Clinical and radiological charts were reviewed to find patients' demographic, pathologic and radiologic features in hydrocephalic and non-hydrocephalic patients. In the hydrocephalus cohort, treatment strategy and its effectiveness and complications were analyzed.

RESULTS

Ninety-four pediatric patients were enrolled in the study. Patients who developed hydrocephalus showed significantly lesser maximum axial tumor areas than patients without hydrocephalus (respectively 6.5 cm² vs 16.45 cm², p < 0.005). Hydrocephalus developed in 33 patients (35%) with an onset interval of 5.24 ± 1.21 months (range 3.2-7.3). The majority of hydrocephalic patients (28 cases, 90%) were treated by ventriculoperitoneal shunt, the remaining 3 patients being treated by endoscopic third ventriculostomy. Mean overall survival was 16.6 months ± 20 months without significative difference between the groups.

CONCLUSION

The onset of hydrocephalus occurs in the first moths of the disease story and found a negative correlation with tumor maximal axial diameter. Early treatment of hydrocephalus presents a very low complications rate with satisfying clinical outcome, as it allows the patients to continue the neurooncological therapies being a part of the treatment armamentarium instead of a palliative solution.

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.

A comparative study of brain tumor cells from different age and anatomical locations using 3D biomimetic hydrogels

Brain tumors exhibit vast genotypic and phenotypic diversity depending on patient age and anatomical location. Hydrogels hold great promise as 3D in vitro models for studying brain tumor biology and drug screening, yet previous studies were limited to adult glioblastoma cells, and most studies used immortalized cell lines. Here we report a hydrogel platform that supports the proliferation and invasion of patient-derived brain tumor cell cultures (PDCs) isolated from different patient age groups and anatomical locations. Hydrogel stiffness was tuned by varying poly(ethylene-glycol) concentration. Cell adhesive peptide (CGRDS), hyaluronic acid, and MMP-cleavable crosslinkers were incorporated to facilitate cell adhesion and cell-mediated degradation. Three PDC lines were compared including adult glioblastoma cells (aGBM), pediatric glioblastoma cells (pGBM), and diffuse pontine intrinsic glioma (DIPG). A commonly used immortalized adult glioblastoma cell line U87 was included as a control. PDCs displayed stiffness-dependent behavior, with 40 Pa hydrogel promoting faster tumor proliferation and invasion. Adult GBM cells exhibited faster proliferation than pediatric GBM, and DIPG showed slowest proliferation. These results suggest both patient age and tumor location affects brain tumor behaviors. Adult GBM PDCs also exhibited very different cell proliferation and morphology from U87. The hydrogel reported here can provide a useful tool for future studies to better understand how age and anatomical locations impacts brain tumor progression using 3D in vitro models.

High Prevalence of Developmental Venous Anomaly in Diffuse Intrinsic Pontine Gliomas: A Pediatric Control Study

BACKGROUND

No link has been demonstrated between diffuse intrinsic pontine glioma and developmental venous anomaly in pediatric patients.

OBJECTIVE

To determine the prevalence of developmental venous anomaly in a pediatric cohort of diffuse intrinsic pontine glioma.

METHODS

We performed a retrospective cohort study (1998-2017) of consecutive pediatric patients harboring a diffuse intrinsic pontine glioma (experimental set, n = 162) or a craniopharyngioma (control set, n = 142) in a tertiary pediatric neurosurgical center. The inclusion criteria were the following: age <18 yr at diagnosis; histopathological diagnosis of diffuse intrinsic pontine glioma or craniopharyngioma according to the 2016 World Health Organization classification of tumors of the central nervous system; no previous oncological treatment; and available preoperative magnetic resonance imaging performed with similar acquisition protocol.

RESULTS

We found a significantly higher prevalence of developmental venous anomaly in the experimental set of 162 diffuse intrinsic pontine gliomas (24.1%) than in the control set of 142 craniopharyngiomas (10.6%; P = .001). The prevalence of developmental venous anomalies was not significantly impacted by demographic data (sex, age at diagnosis, and underlying pathological condition), biomolecular analysis (H3-K27M-mutant subgroup, H3.1-K27M-mutant subgroup, and H3.3-K27M-mutant subgroup), or imaging findings (anatomic location, anatomic extension, side, and obstructive hydrocephalus) of the studied diffuse intrinsic pontine gliomas.

CONCLUSION

We report a higher prevalence of developmental venous anomaly in pediatric diffuse intrinsic pontine glioma patients than in control patients, which suggests a potential underlying common predisposition or a causal relationship that will require deeper investigations.

A phase I/II study of ribociclib following radiation therapy in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG)

PURPOSE

Cyclin-dependent kinase-retinoblastoma (CDK-RB) pathway is dysregulated in some diffuse intrinsic pontine gliomas (DIPG). We evaluated safety, feasibility, and early efficacy of the CDK4/6-inhibitor ribociclib, administered following radiotherapy in newly-diagnosed DIPG patients.

METHODS

Following radiotherapy, eligible patients received ribociclib in 28-day cycles (350 mg/m²; 21 days on/7 days off). Feasibility endpoints included tolerability for at least 6 courses, and a less than 2-week delay in restarting therapy after 1 dose reduction. Early efficacy was measured by 1-year and median overall survival (OS). Patient/parent-by-proxy reported outcomes measurement information system (PROMIS) assessments were completed prospectively.

RESULTS

The study included 10 evaluable patients, 9 DIPG and 1 diffuse midline glioma (DMG)-all 3.7 to 19.8 years of age. The median number of courses was 8 (range 3-14). Three patients required dose reduction for grade-4 neutropenia, and 1 discontinued therapy for hematological toxicity following course 4. The most common grade-3/4 toxicity was myelosuppression. After 2 courses, MRI evaluations in 4 patients revealed increased necrotic volume, associated with new neurological symptoms in 3 patients. The 1-year and median OS for DIPG was 89% and 16.1 months (range 10-30), respectively; the DMG patient died at 6 months post-diagnosis. Five patients donated brain tissue and tumor; 3 were RB+ .

CONCLUSIONS

Ribociclib administered following radiotherapy is feasible in DIPG and DMG. Increased tumor necrosis may represent a treatment effect. These data warrant further prospective volumetric analyses of tumors with necrosis. Feasibility and stabilization findings support further investigation of ribociclib in combination therapies.

TRIAL REGISTRATION

NCT02607124.