Feasibility, safety, and indications for surgical biopsy of intrinsic brainstem tumors in children

Safety and Technical Efficacy of Pediatric Brainstem Biopsies: An Updated Meta-Analysis of 1000+ Children

BACKGROUND

Brainstem tumors represent ∼10% of pediatric brain tumors, ∼80% of these are diffuse midline glioma. Given invariably poor prognosis in diffuse midline glioma, there continues to be immense variation worldwide in performing biopsy of these lesions. Several contemporary studies in recent years have provided new data to elucidate the safety profile of biopsy and an updated meta-analysis is thus indicated.

METHODS

We found 29 studies of pediatric brainstem biopsy in the last 20 years (2003-2023, 1002 children). We applied meta-analysis of proportions using a random-effects model to generate point estimates, confidence intervals, and measures of heterogeneity.

RESULTS

Eighty-seven percent of procedures were stereotactic needle biopsies (of these, 62% with a frame, 14% without frame, and 24% robotic.) Biopsy resulted in a histological diagnosis ("technical yield") in 96.8% of cases (95% CI 95.4-98.2). Temporary complications were seen in 6% (95 CI 4-8), with the most common neurological complications being 1) cranial nerve dysfunction, 2) worsening or new ataxia, and 3) limb weakness. Permanent complications (excluding death) were seen in 1% (95% CI 0.5-2), most commonly including cranial nerve dysfunction and limb weakness. Five deaths were reported in the entire pooled cohort of 1002 children (0.5%).

CONCLUSIONS

When counseling families on the merits of brainstem biopsy in children, it is reasonable to state that permanent morbidity is rare (<2%). If biopsy is performed specifically to facilitate enrollment in clinical trials requiring a molecular diagnosis, the risks of biopsy outlined here should be weighed against potential benefits of trial enrollment.

The Landscape of Pediatric High-Grade Gliomas: The Virtues and Pitfalls of Pre-Clinical Models

Pediatric high-grade gliomas (pHGG) are malignant and usually fatal central nervous system (CNS) WHO Grade 4 tumors. The majority of pHGG consist of diffuse midline gliomas (DMG), H3.3 or H3.1 K27 altered, or diffuse hemispheric gliomas (DHG) (H3.3 G34-mutant). Due to diffuse tumor infiltration of eloquent brain areas, especially for DMG, surgery has often been limited and chemotherapy has not been effective, leaving fractionated radiation to the involved field as the current standard of care. pHGG has only been classified as molecularly distinct from adult HGG since 2012 through Next-Generation sequencing approaches, which have shown pHGG to be epigenetically regulated and specific tumor sub-types to be representative of dysregulated differentiating cells. To translate discovery research into novel therapies, improved pre-clinical models that more adequately represent the tumor biology of pHGG are required. This review will summarize the molecular characteristics of different pHGG sub-types, with a specific focus on histone K27M mutations and the dysregulated gene expression profiles arising from these mutations. Current and emerging pre-clinical models for pHGG will be discussed, including commonly used patient-derived cell lines and in vivo modeling techniques, encompassing patient-derived xenograft murine models and genetically engineered mouse models (GEMMs). Lastly, emerging techniques to model CNS tumors within a human brain environment using brain organoids through co-culture will be explored. As models that more reliably represent pHGG continue to be developed, targetable biological and genetic vulnerabilities in the disease will be more rapidly identified, leading to better treatments and improved clinical outcomes.

Clinical protocol: Feasibility of evaluating abemaciclib neuropharmacokinetics of diffuse midline glioma using intratumoral microdialysis

Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates <10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment responsivity. This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are >10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. Trial registration: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis.

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.

Therapeutic avenues for targeting treatment challenges of diffuse midline gliomas

Diffuse midline glioma (DMG) is the leading cause of brain tumor-related deaths in children. DMG typically presents with variable neurologic symptoms between ages 3 and 10. Currently, radiation remains the standard therapy for DMG to halt progression and reduce tumor bulk to minimize symptoms. However, tumors recur in almost 100% of patients and thus, DMG is still considered an incurable cancer with a median survival of 9-12 months. Surgery is generally contraindicated due to the delicate organization of the brainstem, where DMG is located. Despite extensive research efforts, no chemotherapeutic agents, immune therapies, or molecularly targeted therapies have been approved to provide survival benefit. Furthermore, the efficacy of therapies is limited by poor blood-brain barrier penetration and inherent resistance mechanisms of the tumor. However, novel drug delivery approaches, along with recent advances in molecularly targeted therapies and immunotherapies, have advanced to clinical trials and may provide viable future treatment options for DMG patients. This review seeks to evaluate current therapeutics at the preclinical stage and those that have advanced to clinical trials and to discuss the challenges of drug delivery and inherent resistance to these therapies.

Pediatric Glioma Models Provide Insights into Tumor Development and Future Therapeutic Strategies

In depth study of pediatric gliomas has been hampered due to difficulties in accessing patient tissue and a lack of clinically representative tumor models. Over the last decade, however, profiling of carefully curated cohorts of pediatric tumors has identified genetic drivers that molecularly segregate pediatric gliomas from adult gliomas. This information has inspired the development of a new set of powerful in vitro and in vivo tumor models that can aid in identifying pediatric-specific oncogenic mechanisms and tumor microenvironment interactions. Single-cell analyses of both human tumors and these newly developed models have revealed that pediatric gliomas arise from spatiotemporally discrete neural progenitor populations in which developmental programs have become dysregulated. Pediatric high-grade gliomas also harbor distinct sets of co-segregating genetic and epigenetic alterations, often accompanied by unique features within the tumor microenvironment. The development of these novel tools and data resources has led to insights into the biology and heterogeneity of these tumors, including identification of distinctive sets of driver mutations, developmentally restricted cells of origin, recognizable patterns of tumor progression, characteristic immune environments, and tumor hijacking of normal microenvironmental and neural programs. As concerted efforts have broadened our understanding of these tumors, new therapeutic vulnerabilities have been identified, and for the first time, promising new strategies are being evaluated in the preclinical and clinical settings. Even so, dedicated and sustained collaborative efforts are necessary to refine our knowledge and bring these new strategies into general clinical use. In this review, we will discuss the range of currently available glioma models, the way in which they have each contributed to recent developments in the field, their benefits and drawbacks for addressing specific research questions, and their future utility in advancing biological understanding and treatment of pediatric glioma.

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.

Pediatric diffuse midline glioma H3K27- altered: A complex clinical and biological landscape behind a neatly defined tumor type

The 2021 World Health Organization Classification of Tumors of the Central Nervous System, Fifth Edition (WHO-CNS5), has strengthened the concept of tumor grade as a combination of histologic features and molecular alterations. The WHO-CNS5 tumor type "Diffuse midline glioma, H3K27-altered," classified within the family of "Pediatric-type diffuse high-grade gliomas," incarnates an ideally perfect integrated diagnosis in which location, histology, and genetics clearly define a specific tumor entity. It tries to evenly characterize a group of neoplasms that occur primarily in children and midline structures and that have a dismal prognosis. Such a well-defined pathological categorization has strongly influenced the pediatric oncology community, leading to the uniform treatment of most cases of H3K27-altered diffuse midline gliomas (DMG), based on the simplification that the mutation overrides the histological, radiological, and clinical characteristics of such tumors. Indeed, multiple studies have described pediatric H3K27-altered DMG as incurable tumors. However, in biology and clinical practice, exceptions are frequent and complexity is the rule. First of all, H3K27 mutations have also been found in non-diffuse gliomas. On the other hand, a minority of DMGs are H3K27 wild-type but have a similarly poor prognosis. Furthermore, adult-type tumors may rarely occur in children, and differences in prognosis have emerged between adult and pediatric H3K27-altered DMGs. As well, tumor location can determine differences in the outcome: patients with thalamic and spinal DMG have significantly better survival. Finally, other concomitant molecular alterations in H3K27 gliomas have been shown to influence prognosis. So, when such additional mutations are found, which one should we focus on in order to make the correct clinical decision? Our review of the current literature on pediatric diffuse midline H3K27-altered DMG tries to address such questions. Indeed, H3K27 status has become a fundamental supplement to the histological grading of pediatric gliomas; however, it might not be sufficient alone to exhaustively define the complex biological behavior of DMG in children and might not represent an indication for a unique treatment strategy across all patients, irrespective of age, additional molecular alterations, and tumor location.

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.

Brainstem Surgery: Functional Surgical Anatomy with the Use of an Advanced Modern Intraoperative Neurophysiological Procedure

Intraoperative neurophysiology (ION) in brainstem surgery evolved as brainstem surgery advanced.The original idea of brainstem mapping (BSM) is a neurophysiological procedure to locate cranial nerve motor nuclei (CNMN) on the floor of the fourth ventricle. With the introduction of various skull base approaches to the brainstem, BSM is carried out on any surface of the brainstem to expose the safe entry zone to the intrinsic brainstem lesion. It is the modern concept of BSM, a broader definition of BSM. BSM enables to avoid direct damage to the CNMN when approaching the brainstem through the negative mapping region.The corticobulbar tract (CBT) motor evoked potential (MEP) is another ION procedure in brainstem surgery. It enables monitoring of the functional integrity of the whole cranial motor pathway without interrupting surgical procedures. Combined application of both BSM and CBT-MEP monitoring is indispensable for the functional preservation of the CNMN and their supranuclear innervation during the brainstem surgery.In this paper, the neurophysiological aspect of BSM and the CBT-MEP was fully described. Normal anatomical background of the floor of the fourth ventricle and the detail of the CBT anatomy were demonstrated to better understand their clinical usefulness, limitations, and surgical implications derived from ION procedures. Finally, a future perspective in the role of ION procedures in brainstem surgery was presented. The latest magnetic resonance imaging (MRI) technology can allow surgeons to find an "on the image" safe entry zone to the brainstem. However, the role of BSM and the CBT-MEP monitoring in terms of safe brainstem surgery stays unshakable. Special attention was paid for the recent trend of management in diffuse intrinsic pontine gliomas. A new role of BSM during a stereotactic biopsy was discussed.It is the authors' expectation that the paper enhances the clinical application of a contemporary standard of the ION in brainstem surgery and supports safer brainstem surgery more than ever and in the future.

Structural variants shape driver combinations and outcomes in pediatric high-grade glioma

We analyzed the contributions of structural variants (SVs) to gliomagenesis across 179 pediatric high-grade gliomas (pHGGs). The most recurrent SVs targeted MYC isoforms and receptor tyrosine kinases (RTKs), including an SV amplifying a MYC enhancer in 12% of diffuse midline gliomas (DMG), indicating an underappreciated role for MYC in pHGG. SV signature analysis revealed that tumors with simple signatures were TP53 wild type (TP53WT) but showed alterations in TP53 pathway members PPM1D and MDM4. Complex signatures were associated with direct aberrations in TP53, CDKN2A and RB1 early in tumor evolution and with later-occurring extrachromosomal amplicons. All pHGGs exhibited at least one simple-SV signature, but complex-SV signatures were primarily restricted to subsets of H3.3K27M DMGs and hemispheric pHGGs. Importantly, DMGs with complex-SV signatures were associated with shorter overall survival independent of histone mutation and TP53 status. These data provide insight into the impact of SVs on gliomagenesis and the mechanisms that shape them.

Treatment Limitations for Pediatric Diffuse Intrinsic Pontine Gliomas in a Middle-Income Country

Objectives To evaluate the surgical management outcomes in pediatric patients with diffuse intrinsic pontine gliomas (DIPGs) who underwent intended biopsies and partial resections in a middle-income country, highlighting the barriers and challenges of these procedures for further investigation.

Methods A retrospective review of a prospective acquired series of patients who underwent biopsy or resection for DIPG between January 2012 and June 2018 at our institution was performed.

Results A total of 43 patients with posterior fossa tumors were identified. From these, seven pediatric DIPG cases were enrolled. Five were males. The median age was 5 years (range: 1–12 years). Only one patient (14.3%) had a ganglioglioma, while the others presented pilocytic and diffuse astrocytomas. Two (28.6%) patients had an intentional biopsy, and the other five (71.4%) had a partial resection. In the three (28.6%) patients who presented with associated hydrocephalus, the endoscopic third ventriculostomy was performed in the same surgical time. The median preoperative Lansky play-performance scale (LPPS) was 80 (range: 60–100), while the median postoperative LPPS was 23 (range: 7–52).

Conclusion A decrease in overall survival was noted compared with data reported in other series. Multifactorial barriers were discussed including the social, geographic, and economic features that may influence on final outcomes.

Diffuse Intrinsic Pontine Glioma: Molecular Landscape, Evolving Treatment Strategies and Emerging Clinical Trials

Diffuse intrinsic pontine glioma (DIPG) is a type of intrinsic brainstem glial tumor that occurs primarily in the pediatric population. DIPG is initially diagnosed based on clinical symptoms and the characteristic location on imaging. Histologically, these tumors are characterized by a heterogenous population of cells with multiple genetic mutations and high infiltrative capacity. The most common mutation seen in this group is a lysine to methionine point mutation seen at position 27 (K27M) within histone 3 (H3). Tumors with the H3 K27M mutation, are considered grade 4 and are now categorized within the H3 K27-altered diffuse midline glioma category by World Health Organization classification. Due to its critical location and aggressive nature, DIPG is resistant to the most eradicative treatment and is universally fatal; however, modern advances in the surgical techniques resulting in safe biopsy of the lesion have significantly improved our understanding of this disease at the molecular level. Genomic analysis has shown several mutations that play a role in the pathophysiology of the disease and can be targeted therapeutically. In this review, we will elaborate on DIPG from general aspects and the evolving molecular landscape. We will also review innovative therapeutic options that have been trialed along with new promising treatments on the horizon.

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 pilot radiogenomic study of DIPG reveals distinct subgroups with unique clinical trajectories and therapeutic targets

An adequate understanding of the relationships between radiographic and genomic features in diffuse intrinsic pontine glioma (DIPG) is essential, especially in the absence of universal biopsy, to further characterize the molecular heterogeneity of this disease and determine which patients are most likely to respond to biologically-driven therapies. Here, a radiogenomics analytic approach was applied to a cohort of 28 patients with DIPG. Tumor size and imaging characteristics from all available serial MRIs were evaluated by a neuro-radiologist, and patients were divided into three radiographic response groups (partial response [PR], stable disease [SD], progressive disease [PD]) based on MRI within 2 months of radiotherapy (RT) completion. Whole genome and RNA sequencing were performed on autopsy tumor specimens. We report several key, therapeutically-relevant findings: (1) Certain radiologic features on first and subsequent post-RT MRIs are associated with worse overall survival, including PD following irradiation as well as present, new, and/or increasing peripheral ring enhancement, necrosis, and diffusion restriction. (2) Upregulation of EMT-related genes and distant tumor spread at autopsy are observed in a subset of DIPG patients who exhibit poorer radiographic response to irradiation and/or higher likelihood of harboring H3F3A mutations, suggesting possible benefit of upfront craniospinal irradiation. (3) Additional genetic aberrations were identified, including DYNC1LI1 mutations in a subgroup of patients with PR on post-RT MRI; further investigation into potential roles in DIPG tumorigenesis and/or treatment sensitivity is necessary. (4) Whereas most DIPG tumors have an immunologically “cold” microenvironment, there appears to be a subset which harbor a more inflammatory genomic profile and/or higher mutational burden, with a trend toward improved overall survival and more favorable radiographic response to irradiation, in whom immunotherapy should be considered. This study has begun elucidating relationships between post-RT radiographic response with DIPG molecular profiles, revealing radiogenomically distinct subgroups with unique clinical trajectories and therapeutic targets.

A Protocol for the Generation of Treatment-naïve Biopsy-derived Diffuse Intrinsic Pontine Glioma and Diffuse Midline Glioma Models

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal tumor of the brainstem, most commonly affecting young children. Due to its location, surgical resection is not achievable, but consideration of a biopsy has become standard practice at children’s hospitals with the appropriate neurosurgical expertise. While the decision to obtain a biopsy should be directed by the presence of atypical radiographic features that call the diagnosis of DIPG into question or the requirement of biopsy tissue for clinical trial enrollment, once this precious tissue is available its use for research should be considered. The majority of DIPG and diffuse midline glioma, H3 K27M-mutant (DMG) models are autopsy-derived or genetically-engineered, each of which has limitations for translational studies, so the use of biopsy tissue for laboratory model development provides an opportunity to create unique model systems. Here, we present a detailed laboratory protocol for the generation of treatment-naïve biopsy-derived DIPG/DMG models.

Diffuse infiltrative pontine glioma biopsy in children with neuronavigation, frameless procedure: A single center experience of 10 cases

INTRODUCTION

This study presented pediatric DIPG 's biopsy with frameless Neuronavigation.

PATIENTS AND METHODS

We report our experience about 10 patients who had Diffuse Intrinsic Pontine Glioma between 2014 and 2018. All patients were biopsied with BrainLab Varioguide Neuronavigation®. We always used fusion between specific CT Scan and MRI to selected target, made planning and biopsies. All patients were included in BIOMEDE after scientific and ethic discussions. We always selected a trans-cerebellar trajectory and made same procedure (lot of biopsies at one level). All patients have MRI at J1 to verify site of biopsy and to eliminate complication.

RESULTS

The average age was 8.1 years. Symptoms were common with principally headaches and nystagmus. All biopsies were contributive for histopathological diagnosis and establish molecular profile for molecular study. We have no definitive morbidity and procedure duration was 93minutes in average. All MRI didn't showed intracranial complication after procedure and showed great precision of biopsy compared with the selected target.

DISCUSSION

We reviewed the literature and compare our results with series of DIPG biopsies using stereotactic frame or robotic assisted frameless. It was a safe, accuracy and easiness procedure. We always have histopathological and molecular result to proceed next step of treatment. This modality is an alternative possibility to biopsy very young patients with low morbidity.

Variations in attitudes towards stereotactic biopsy of adult diffuse midline glioma patients: a survey of members of the AANS/CNS Tumor Section

Purpose

Diffuse midline gliomas are rare midline CNS malignancies that primarily affect children but can also affect adults. While radiation is standard treatment, prognosis remains fatal. Furthermore, due to its sensitive anatomic location, many physicians have been reluctant to perform biopsies without potential for improved prognosis. However, recent advancements in molecular-targeted therapeutics have encouraged greater tissue sampling. While the literature reflects this progress, the landscape of how clinicians actually manage these patients remains unclear. Our goal was to assess the attitudes of current practicing neurosurgical oncologists towards management of adult diffuse midline gliomas, reasons behind their practices, and factors that might influence these practices.

Methods

We created and distributed a survey with 16 multiple choice and open-ended questions to members of the Tumor Section of the Congress of Neurological Surgeons.

Results

A total of 81 physicians responded to the survey. Although time since training and volume of glioma patients did not significantly affect the decision to consider clinical trials or to offer biopsy, those that operated on fewer gliomas (< 25/year) were more likely to cite surgical morbidity as the primary reason not to biopsy these midline locations. Further, surgeons with access to more advanced molecular testing were significantly more likely to consider clinical trial eligibility when offering biopsies.

Conclusion

Factors that affect the management of diffuse midline gliomas and the role of biopsy are relatively uniform across the field, however, there were a few notable differences that reflect the changes within the neuro-oncology field in response to clinical trials.

Electronic supplementary material

The online version of this article (10.1007/s11060-020-03585-7) contains supplementary material, which is available to authorized users.

Convection Enhanced Delivery for Diffuse Intrinsic Pontine Glioma: Review of a Single Institution Experience

Diffuse intrinsic pontine gliomas (DIPGs) are a pontine subtype of diffuse midline gliomas (DMGs), primary central nervous system (CNS) tumors of childhood that carry a terrible prognosis. Because of the highly infiltrative growth pattern and the anatomical position, cytoreductive surgery is not an option. An initial response to radiation therapy is invariably followed by recurrence; mortality occurs approximately 11 months after diagnosis. The development of novel therapeutics with great preclinical promise has been hindered by the tightly regulated blood-brain barrier (BBB), which segregates the tumor comportment from the systemic circulation. One possible solution to this obstacle is the use of convection enhanced delivery (CED), a local delivery strategy that bypasses the BBB by direct infusion into the tumor through a small caliber cannula. We have recently shown CED to be safe in children with DIPG (NCT01502917). In this review, we discuss our experience with CED, its advantages, and technical advancements that are occurring in the field. We also highlight hurdles that will likely need to be overcome in demonstrating clinical benefit with this therapeutic strategy.

Pontine gliomas a 10-year population-based study: a report from The Canadian Paediatric Brain Tumour Consortium (CPBTC)

BACKGROUND

Diffuse intrinsic pontine gliomas (DIPG) are midline gliomas that arise from the pons and the majority are lethal within a few months after diagnosis. Due to the lack of histological diagnosis the epidemiology of DIPG is not completely understood. The aim of this report is to provide population-based data to characterize the descriptive epidemiology of this condition in Canadian children.

PATIENTS AND METHODS

A national retrospective study of children and adolescents diagnosed with DIPG between 2000 and 2010 was undertaken. All cases underwent central review to determine clinical and radiological diagnostic characteristics. Crude incidence figures were calculated using age-adjusted (0-17 year) population data from Statistics Canada. Survival analyses were performed using the Kaplan-Meier method.

RESULTS

A total of 163 patients with pontine lesions were identified. Central review determined one-hundred and forty-three patients who met clinical, radiological and/or histological criteria for diagnosis. We estimate an incidence rate of 1.9 DIPG/1,000,000 children/year in the Canadian population over a 10 years period. Median age at diagnosis was 6.8 years and 50.3% of patients were female. Most patients presented with cranial nerve palsies (76%) and ataxia (66%). Despite typical clinical and radiological characteristics, histological confirmation reported three lesions to be low-grade gliomas and three were diagnosed as CNS embryonal tumor not otherwise specified (NOS).

CONCLUSIONS

Our study highlights the challenges associated with epidemiology studies on DIPG and the importance of central review for incidence rate estimations. It emphasizes that tissue biopsies are required for accurate histological and molecular diagnosis in patients presenting with pontine lesions and reinforces the limitations of radiological and clinical diagnosis in DIPG. Likewise, it underscores the urgent need to increase the availability and accessibility to clinical trials.

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.

Diffuse intrinsic pontine gliomas: Diagnostic approach and treatment strategies

Diffuse intrinsic pontine gliomas (DIPG) are high grade gliomas of the brainstem with fatal outcomes. Radiation is known to be partially effective to control the immediate flare but relapse is frequent. There has been ongoing research to study the role of molecular subgroups and identification of specific targets but this is not possible with histopathological diagnosis alone. The authors' objective is to highlight the need for and discuss ongoing molecular research. There is an inherent need for the availability of tumor tissue to be able to conduct research studies. The authors advocate the use of neuronavigation assisted stereotactic technique for tumor biopsy. The technique is feasible with a predefined surgical trajectory. After obtaining tissue diagnosis further work can be performed to isolate and identify histone protein genetic mutations and methylation changes responsible for DIPG molecular subgrouping. Moreover, convection enhanced delivery of therapeutic agents is being developed for better instillation of future drug agents. Despite identification of genetic/epigenetic mutations, growth factors, receptors, and tissue biomarkers, the oncogenesis of DIPG remains elusive. The authors' effort to provide a comprehensive review on DIPG to better understand the disease, need for tissue diagnosis, described surgical technique, and need for pre-clinical and clinical future research is novel.

Diffuse Intrinsic Pontine Glioma: From Diagnosis to Next-Generation Clinical Trials

PURPOSE OF REVIEW

This review of diffuse intrinsic pontine glioma (DIPG) provides clinical background, a systematic approach to diagnosis and initial care, and synthesizes historical, modern, and future directions for treatment. We present evidence supporting neurosurgical biopsy, early palliative care involvement, limitation of glucocorticoid use, and the leveraging of preclinical DIPG models as a pipeline to next-generation clinical trials.

RECENT FINDINGS

New molecular understanding of pediatric high-grade gliomas has led to the reclassification of DIPG as one member of a family of diffuse gliomas occurring in the midline of the central nervous system that exhibit pathognomonic mutations in genes encoding histone 3 (H3 K27M). DIPG remains a clinically relevant term, though diagnostically the 80% of DIPG cases that exhibit the H3 K27M mutation have been reclassified as diffuse midline glioma, H3 K27M-mutant. Re-irradiation has been shown to be well-tolerated and of potential benefit. Epigenetic targeting of transcriptional dependencies in preclinical models is fueling molecularly targeted clinical trials. Chimeric antigen receptor T cell immunotherapy has also demonstrated efficacy in preclinical models and provides a promising new clinical strategy. DIPG is a universally fatal, epigenetically driven tumor of the pons that is considered part of a broader class of diffuse midline gliomas sharing H3 K27M mutations. Radiation remains the standard of care, single-agent temozolomide is not recommended, and glucocorticoids should be used only sparingly. A rapid evolution of understanding in the chromatin, signaling, and immunological biology of DIPG may soon result in clinical breakthroughs.

A pilot precision medicine trial for children with diffuse intrinsic pontine glioma-PNOC003: A report from the Pacific Pediatric Neuro-Oncology Consortium

This clinical trial evaluated whether whole exome sequencing (WES) and RNA sequencing (RNAseq) of paired normal and tumor tissues could be incorporated into a personalized treatment plan for newly diagnosed patients (<25 years of age) with diffuse intrinsic pontine glioma (DIPG). Additionally, whole genome sequencing (WGS) was compared to WES to determine if WGS would further inform treatment decisions, and whether circulating tumor DNA (ctDNA) could detect the H3K27M mutation to allow assessment of therapy response. Patients were selected across three Pacific Pediatric Neuro-Oncology Consortium member institutions between September 2014 and January 2016. WES and RNAseq were performed at diagnosis and recurrence when possible in a CLIA-certified laboratory. Patient-derived cell line development was attempted for each subject. Collection of blood for ctDNA was done prior to treatment and with each MRI. A specialized tumor board generated a treatment recommendation including up to four FDA-approved agents based upon the genomic alterations detected. A treatment plan was successfully issued within 21 business days from tissue collection for all 15 subjects, with 14 of the 15 subjects fulfilling the feasibility criteria. WGS results did not significantly deviate from WES-based therapy recommendations; however, WGS data provided further insight into tumor evolution and fidelity of patient-derived cell models. Detection of the H3F3A or HIST1H3B K27M (H3K27M) mutation using ctDNA was successful in 92% of H3K27M mutant cases. A personalized treatment recommendation for DIPG can be rendered within a multicenter setting using comprehensive next-generation sequencing technology in a clinically relevant timeframe.

High frequency of H3 K27M mutations in adult midline gliomas

PURPOSE

Diffuse midline gliomas, H3 K27M-mutant were introduced as a new grade IV entity in WHO classification of tumors 2016. These tumors occur often in pediatric patients and show an adverse prognosis with a median survival less than a year. Most of the studies on these tumors, previously known as pediatric diffuse intrinsic pontine glioma, are on pediatric patients and its significance in adult patients is likely underestimated.

METHODS

We studied 165 cases of brain tumors of midline localization initially diagnosed as diffuse astrocytomas, oligodendrogliomas, pilocytic astrocytomas, supependymomas, ependymomas and medulloblastomas in patients with an age range of 2-85.

RESULTS

We identified 41 diffuse midline gliomas according WHO 2016, including 12 pediatric and 29 adult cases, among them two cases with histological features of low grade tumors: pilocytic astrocytoma and subependymoma. 49% (20/41) of the patients were above 30 years old by the first tumor manifestation including 29% (11/41) above 54 that signifies a broader age spectrum as previously reported. Our study confirms that H3 K27M mutations are associated with a poorer prognosis in pediatric patients compared to wild-type tumors, while in adult patients these mutations do not influence the survival significantly. The pattern of tumor growth was different in pediatric compared to adult patients; a diffuse growth along the brain axis was more evident in adult compared to pediatric patients (24% vs. 15%).

CONCLUSION

H3 K27M mutations are frequent in adult midline gliomas and have a prognostic role similar to H3 K27M wild-type high-grade tumors.

International experience in the development of patient-derived xenograft models of diffuse intrinsic pontine glioma

PURPOSE

Diffuse intrinsic pontine glioma is the most aggressive form of high grade glioma in children with no effective therapies. There have been no improvements in survival in part due poor understanding of underlying biology, and lack of representative in vitro and in vivo models. Recently, it has been found feasible to use both biopsy and autopsy tumors to generate cultures and xenograft models.

METHODS

To further model development, we evaluated the collective international experience from 8 collaborating centers to develop DIPG pre-clinical models from patient-derived autopsies and biopsies. Univariate and multivariate analysis was performed to determine key factors associated with the success of in vitro and in vivo PDX development.

RESULTS

In vitro cultures were successfully established from 57% of samples (84.2% of biopsies and 38.2% of autopsies). Samples transferred in DMEM media were more likely to establish successful culture than those transported in Hibernate A. In vitro cultures were more successful from biopsies (84.2%) compared with autopsies (38.2%) and as monolayer on laminin-coated plates than as neurospheres. Primary cultures successfully established from autopsy samples were more likely to engraft in animal models than cultures established from biopsies (86.7% vs. 47.4%). Collectively, tumor engraftment was more successful when DIPG samples were directly implanted in mice (68%), rather than after culturing (40.7%).

CONCLUSION

This multi-center study provides valuable information on the success rate of establishing patient-derived pre-clinical models of DIPG. The results can lead to further optimization of DIPG model development and ultimately assist in the investigation of new therapies for this aggressive pediatric brain tumor.

Prospective feasibility and safety assessment of surgical biopsy for patients with newly diagnosed diffuse intrinsic pontine glioma

Background

Diagnosis of diffuse intrinsic pontine glioma (DIPG) has relied on imaging studies, since the appearance is pathognomonic, and surgical risk was felt to be high and unlikely to affect therapy. The DIPG Biology and Treatment Study (DIPG-BATS) reported here incorporated a surgical biopsy at presentation and stratified subjects to receive FDA-approved agents chosen on the basis of specific biologic targets.

Methods

Subjects were eligible for the trial if the clinical features and imaging appearance of a newly diagnosed tumor were consistent with a DIPG. Surgical biopsies were performed after enrollment and prior to definitive treatment. All subjects were treated with conventional external beam radiotherapy with bevacizumab, and then stratified to receive bevacizumab with erlotinib or temozolomide, both agents, or neither agent, based on O6-methylguanine-DNA methyltransferase status and epidermal growth factor receptor expression. Whole-genome sequencing and RNA sequencing were performed but not used for treatment assignment.

Results

Fifty-three patients were enrolled at 23 institutions, and 50 underwent biopsy. The median age was 6.4 years, with 24 male and 29 female subjects. Surgical biopsies were performed with a specified technique and no deaths were attributed to the procedure. Two subjects experienced grade 3 toxicities during the procedure (apnea, n = 1; hypertension, n = 1). One subject experienced a neurologic deficit (left hemiparesis) that did not fully recover. Of the 50 tumors biopsied, 46 provided sufficient tissue to perform the study assays (92%, two-stage exact binomial 90% CI: 83%-97%).

Conclusions

Surgical biopsy of DIPGs is technically feasible, associated with acceptable risks, and can provide biologic data that can inform treatment decisions.

Non-inflammatory tumor microenvironment of diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal malignancy of the childhood central nervous system, with a median overall survival of 9-11 months. We have previously shown that primary DIPG tissue contains numerous tumor-associated macrophages, and substantial work has demonstrated a significant pathological role for adult glioma-associated macrophages. However, work over the past decade has highlighted many molecular and genomic differences between pediatric and adult high-grade gliomas. Thus, we directly compared inflammatory characteristics of DIPG and adult glioblastoma (GBM). We found that the leukocyte (CD45+) compartment in primary DIPG tissue samples is predominantly composed of CD11b + macrophages, with very few CD3+ T-lymphocytes. In contrast, T-lymphocytes are more abundant in adult GBM tissue samples. RNA sequencing of macrophages isolated from primary tumor samples revealed that DIPG- and adult GBM-associated macrophages both express gene programs related to ECM remodeling and angiogenesis, but DIPG-associated macrophages express substantially fewer inflammatory factors than their adult GBM counterparts. Examining the secretome of glioma cells, we found that patient-derived DIPG cell cultures secrete markedly fewer cytokines and chemokines than patient-derived adult GBM cultures. Concordantly, bulk and single-cell RNA sequencing data indicates low to absent expression of chemokines and cytokines in DIPG. Together, these observations suggest that the inflammatory milieu of the DIPG tumor microenvironment is fundamentally different than adult GBM. The low intrinsic inflammatory signature of DIPG cells may contribute to the lack of lymphocytes and non-inflammatory phenotype of DIPG-associated microglia/macrophages. Understanding the glioma subtype-specific inflammatory milieu may inform the design and application of immunotherapy-based treatments.

The Integration of Biology Into the Treatment of Diffuse Intrinsic Pontine Glioma: A Review of the North American Clinical Trial Perspective

Dramatic advances in the molecular analysis of diffuse intrinsic pontine glioma have occurred over the last decade and resulted in the identification of potential therapeutic targets. In spite of these advances, no significant improvement in the outcome has been achieved and median survival remains approximately 10 months. An understanding of the approaches that have been taken to date, why they failed, and how that information can lead the field forward is critical if we are to change the status quo. In this review, we will discuss the clinical trial landscape in North America with an overview of historical approaches that failed and what might account for this failure. We will then provide a discussion of how our understanding of the genotype of this disease has led to the development of a number of trials targeting the mutations and epigenome of diffuse intrinsic pontine gliomas and the issues related to these trials. Similarly, the introduction of methodologies to address penetration across the blood–brain barrier will be considered in the context of both targeted approaches, epigenetic modification, and immune surveillance of these tumors. The comprehensive analysis of these data, generated through cooperative groups, collaborative clinical trials, and pilot studies in North America will be the focus of the IVth Memorial Alicia Pueyo international symposium in Barcelona on March 12th, 2018 and will be compared and contrasted with a similar comprehensive analysis of the European data with the goal of bringing all of these data together to develop a uniform platform on which new rational trials can be based.

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.

Biopsies of pediatric brainstem lesions display low morbidity but strong impact on further treatment decisions

OBJECTIVE

The course of malignant brain stem gliomas in childhood is rarely positive. Because of limited therapeutic options and potentially hazardous biopsies oncologist often relay on MRI diagnoses only for further therapy decisions. In this study we show that brain stem biopsies display a low morbidity rate and neuropathological assessment has a considerable impact on further treatment decision.

METHODS

Within 18-months five children with brainstem symptoms and the radiological diagnosis of a malignant brainstem glioma, were identified. From this time point it was possible to analyze all samples with the 450K methylome analysis. Other neuropathological techniques included classical histology with immunohistochemistry. Surgery was performed as biopsy, either microsurgical, frame-guided (Leksell), robot-assisted (ROSA) or navigated (BrainLab, two children).

RESULTS

Mean age of the children was 7.5years (range: newborn to 12years). There was no biopsy-related morbidity or mortality. The mean number of taken samples was 12 (range: 1-25). Histologic diagnosis could be established in all children, however, 450K methylome diagnosis was positive in only two out of five patients.

CONCLUSION

Despite the technically difficult biopsies, all specimens were sufficient for immunohistochemical diagnosis, however, 450K methylome analysis could only be better established where multiple small samples were taken, instead of few larger ones. Based on the preoperative radiological diagnosis suggesting malignant brainstem glioma, all children would have been treated with combined radiation and temozolomid chemotherapy. Nevertheless, due to the availability of histology and molecular diagnostics, individualized therapy could be performed, preventing in two out of five children from unnecessary radiation and chemotherapy.

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.

A Protocol for Rapid Post-mortem Cell Culture of Diffuse Intrinsic Pontine Glioma (DIPG)

Diffuse Intrinsic Pontine Glioma (DIPG) is a childhood brainstem tumor that carries a universally fatal prognosis. Because surgical resection is not a viable treatment strategy and biopsy is not routinely performed, the availability of patient samples for research is limited. Consequently, efforts to study this disease have been challenged by a paucity of faithful disease models. To address this need, we describe here a protocol for the rapid processing of post-mortem autopsy tissue samples in order to generate durable patient-derived cell culture models that can be used in in vitro assays or in vivo orthotopic xenograft experiments. These models can be used to screen for potential drug targets and to study fundamental pathobiological processes within DIPG. This protocol can further be extended to analyze and isolate tumor and microenvironmental cells using Fluorescence-activated Cell Sorting (FACS), which enables subsequent analysis of gene expression, protein expression, or epigenetic modifications of DNA at the bulk cell or single cell level. Finally, this protocol can also be adapted to generate patient-derived cultures for other central nervous system tumors.

Robot-Assisted Stereotactic Biopsy of Diffuse Intrinsic Pontine Glioma: A Single-Center Experience

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is a childhood tumor with a dismal prognosis. Emerging molecular signatures have paved the way for stereotactic biopsy in selected centers. We present our experience in DIPG stereotactic needle biopsy using the Robotic Stereotactic-Assisted system (ROSA) in a series of consecutive pediatric patients.

METHODS

All stereotactic biopsy procedures for DIPG performed during the last year at our institution were considered. All procedures were carried out using the ROSA surgical assistant through a precoronary approach. All children underwent a postoperative computed tomography scan to document possible surgical complications and confirm the site of biopsy. Postoperative clinical changes were recorded to test morbidity of the procedure.

RESULTS

In the last year, we performed 7 pontine needle biopsies. Specimens were diagnostic and useful for molecular analysis in all cases. No surgical complications were observed. One child showed a transient neurologic worsening related to the biopsy that resolved within 2 weeks. The combination of the precoronary approach and use of the stereotactic ROSA system allowed single-session surgeries in all cases.

CONCLUSIONS

Pontine biopsy for DIPG is a safe procedure in selected centers. The advantages of the single-session procedure we described might be of particular interest in the pediatric setting.

Experimental Therapeutic Trial Design for Pediatric Brain Tumors

Pediatric brain tumors are the leading cause of cancer-related death during childhood. Since the first pediatric brain tumor clinical trials, the field has seen improved outcomes in some, but not all tumor types. In the past few decades, a number of promising new therapeutic agents have emerged, yet only a few of these agents have been incorporated into clinical trials for pediatric brain tumors. In this review, the authors discuss the process of and challenges in pediatric clinical trial design; this will allow for highly efficient and effective clinical trials with appropriate endpoints to ensure rapid and safe investigation of novel therapeutics for children with brain tumors.

Conventional and Advanced Imaging of Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma is the most common brainstem tumor in pediatric patients. This tumor remains one of the most deadly pediatric brain tumors. The diagnosis primarily relies on clinical symptoms and imaging findings. Conventional MRI provides a noninvasive accurate method of diagnosis of these tumors. Advanced MRI techniques are becoming more widely used and studied as additional noninvasive methods to assist clinicians in initial diagnosis and staging, monitoring disease, as well as in surgical and radiation planning. This article will provide an overview of DIPG and describe the typical imaging findings with a focus on advanced imaging techniques.

Diffuse Intrinsic Pontine Glioma: Time for Cautious Optimism

Diffuse intrinsic pontine glioma is a lethal brain cancer that arises in the pons of children. The median survival for children with diffuse intrinsic pontine glioma is less than 1 year from diagnosis, and no improvement in survival has been realized in more than 30 years. Currently, the standard of care for diffuse intrinsic pontine glioma is focal radiation therapy, which provides only temporary relief. Recent genomic analysis of tumors from biopsies and autopsies, have resulted in the discovery of K27M H3.3/H3.1 mutations in 80% and ACVR1 mutations in 25% of diffuse intrinsic pontine gliomas, providing renewed hope for future success in identifying effective therapies. In addition, as stereotactic tumor biopsies at diagnosis at specialized centers have been demonstrated to be safe, biopsies have now been incorporated into several prospective clinical trials. This article summarizes the epidemiology, clinical presentation, diagnosis, prognosis, molecular genetics, current treatment, and future therapeutic directions for diffuse intrinsic pontine glioma.

Pembrolizumab: first experience with recurrent primary central nervous system (CNS) tumors

Patients with progressive primary brain tumors (PBT) are attracted to promising new treatments, even prior to convincing data. Anti-PD1 immunotherapies have been in the spotlight since publication of groundbreaking results for metastatic melanoma with pembrolizumab (PBL). Our objective was to report on the response and toxicity of PBL in patients with advanced PBT. We retrospectively reviewed the charts of 22 patients (17 adults and 5 children) with recurrent central nervous system tumors treated with PBL. We analyzed prior antineoplastic therapies, steroid usage, and outcomes. Patients received a median of two neoplastic therapies prior to PBL, and a median of three infusions of PBL in adults and four in children. Twelve patients (9 adults and 3 children) started PBL on steroids (median dose in adults 4 mg; range 2-8, and in children 1.5 mg, range 0.5-4) and five patients received steroids later during PBL treatment. Twelve patients (10 adults and 2 children) received concomitant bevacizumab with PBL. Side effects were minimal. All patients showed progressive tumor growth during therapy. Median OS from the start of PBL was 2.6 months in adults and 3.2 months in children. Two GB patients underwent tumor resection following treatment with PBL. Tumor-lymphocytic response in these cases was unremarkable, and PD-L1 immuno-staining was negative. In this series of 22 patients with recurrent primary brain tumors, PBL showed no clinical or histologic efficacy. We do not recommend further use of PBL for recurrent PBT unless convincing prospective clinical trial data are published.

Investigational new drugs for brain cancer

INTRODUCTION

Despite substantial improvements in standards of care, the most common aggressive pediatric and adult high-grade gliomas (HGG) carry uniformly fatal diagnoses due to unique treatment limitations, high recurrence rates and the absence of effective treatments following recurrence. Recent advancements in our understanding of the pathophysiology, genetics and epigenetics as well as mechanisms of immune surveillance during gliomagenesis have created new knowledge to design more effective and target-directed therapies to improve patient outcomes.

AREAS COVERED

In this review, the authors discuss the critical genetic, epigenetic and immunologic aberrations found in gliomas that appear rational and promising for therapeutic developments in the presence and future. The current state of the latest therapeutic developments including tumor-specific targeted drug therapies, metabolic targeting, epigenetic modulation and immunotherapy are summarized and suggestions for future directions are offered. Furthermore, they highlight contemporary issues related to the clinical development, such as challenges in clinical trials and toxicities.

EXPERT OPINION

The commitment to understanding the process of gliomagenesis has created a catalogue of aberrations that depict multiple mechanisms underlying this disease, many of which are suitable to therapeutic inhibition and are currently tested in clinical trials. Thus, future treatment endeavors will employ multiple treatment modalities that target disparate tumor characteristics personalized to the patient's individual tumor.

Malignant brainstem tumors in children, excluding diffuse intrinsic pontine gliomas

OBJECT Malignant tumors of the brainstem, excluding classic diffuse intrinsic pontine gliomas (DIPGs), are a very rare, heterogeneous group of neoplasms that have been infrequently described in the literature. In this paper, the authors present their experiences with treating these unique cancers. METHODS A retrospective chart review was conducted to identify eligible cases over a 15-year period. All tumors involving the pons were, by consensus, felt not to be DIPGs based on their neuroimaging features. Demographic information, pathological specimens, neuroimaging characteristics, surgical and nonsurgical management plans, and survival data were gathered for analysis. RESULTS Between January 2000 and December 2014, 29 patients were identified. The mean age at diagnosis was 8.4 years (range 2 months to 25 years), and 17 (59%) patients were male. The most common presenting signs and symptoms were cranial neuropathies (n = 24; 83%), hemiparesis (n = 12; 41%), and ataxia or gait disturbance (n = 10; 34%). There were 18 glial and 11 embryonal tumors. Of the glial tumors, 5 were radiation-induced and 1 was a malignant transformation of a previously known low-grade tumor. Surgical intervention consisted of biopsy alone in 12 patients and some degree of resection in another 15 patients. Two tumors were diagnosed postmortem. The median overall survival for all patients was 196 days (range 15 to 3999 days). There are currently 5 (17%) patients who are still alive: 1 with an anaplastic astrocytoma and the remaining with embryonal tumors. CONCLUSIONS In general, malignant non-DIPG tumors of the brainstem carry a poor prognosis. However, maximal cytoreductive surgery may be an option for select patients with focal tumors. Long-term survival is possible in patients with nonmetastatic embryonal tumors after multimodal treatment, most importantly maximal resection.

DIPG in Children - What Can We Learn from the Past?

Brainstem tumors represent 10–15% of pediatric central nervous system tumors and diffuse intrinsic pontine glioma (DIPG) is the most common brainstem tumor of childhood. DIPG is almost uniformly fatal and is the leading cause of brain tumor-related death in children. To date, radiation therapy (RT) is the only form of treatment that offers a transient benefit in DIPG. Chemotherapeutic strategies including multi-agent neoadjuvant chemotherapy, concurrent chemotherapy with RT, and adjuvant chemotherapy have not provided any survival advantage. To overcome the restrictive ability of the intact blood–brain barrier (BBB) in DIPG, several alternative drug delivery strategies have been proposed but have met with minimal success. Targeted therapies either alone or in combination with RT have also not improved survival. Five decades of unsuccessful therapies coupled with recent advances in the genetics and biology of DIPG have taught us several important lessons (1). DIPG is a heterogeneous group of tumors that are biologically distinct from other pediatric and adult high grade gliomas (HGG). Adapting chemotherapy and targeted therapies that are used in pediatric or adult HGG for the treatment of DIPG should be abandoned (2). Biopsy of DIPG is relatively safe and informative and should be considered in the context of multicenter clinical trials (3). DIPG probably represents a whole brain disease so regular neuraxis imaging is important at diagnosis and during therapy (4). BBB permeability is of major concern in DIPG and overcoming this barrier may ensure that drugs reach the tumor (5). Recent development of DIPG tumor models should help us accurately identify and validate therapeutic targets and small molecule inhibitors in the treatment of this deadly tumor.

Diffuse intrinsic pontine glioma: time for therapeutic optimism

Diffuse intrinsic pontine glioma (DIPG) is an aggressive tumor that is universally fatal, and to-date we are at a virtual standstill in improving its grim prognosis. Dearth of tissue due to rarity of biopsy has precluded understanding the elusive biology and frustration continues in reproducing faithful animal models for translational research. Furthermore the intricate anatomy of the pons has forestalled locoregional therapy and drug penetration. Over the last few years, biopsy-driven targeted therapy, development of vitro and xenograft animal models for therapeutic testing, profiling immunotherapeutic strategies and locoregional infusion of drugs in brain stem tumors, now provide a sense of hope in the years ahead. This review aims to discuss current status and advances in the management of these tumors.

Pathology, Molecular Genetics, and Epigenetics of Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is a devastating pediatric brain cancer with no effective therapy. Histological similarity of DIPG to supratentorial high-grade astrocytomas of adults has led to assumptions that these entities possess similar underlying molecular properties and therefore similar therapeutic responses to standard therapies. The failure of all clinical trials in the last 30 years to improve DIPG patient outcome has suggested otherwise. Recent studies employing next-generation sequencing and microarray technologies have provided a breadth of evidence highlighting the unique molecular genetics and epigenetics of this cancer, distinguishing it from both adult and pediatric cerebral high-grade astrocytomas. This review describes the most common molecular genetic and epigenetic signatures of DIPG in the context of molecular subgroups and histopathological diagnosis, including this tumor entity's unique mutational landscape, copy number alterations, and structural variants, as well as epigenetic changes on the global DNA and histone levels. The increased knowledge of DIPG biology and histopathology has opened doors to new diagnostic and therapeutic avenues.

Managing teenage/young adult (TYA) brain tumors: a UK perspective

Tumors of the CNS are among the commonest malignancies occurring in teenage/young adult patients (i.e., those aged between 15 and 24 years). The treatment of this patient population is challenging. Adolescence and young adulthood are a turbulent period of life, with physical, emotional, social and cognitive changes. Best practice advocates their treatment in dedicated teenage/young adult units, with multidisciplinary team input and access to clinical trials. Treatment of CNS malignancies is dependent upon histological subtype and staging, with varying combinations of surgery, radiotherapy and chemotherapy used. Clinical trials directly targeted at this patient population are rare; treatments are based on pediatric protocols as studies have demonstrated improved outcomes in patients (with other malignancies) treated as such. Scope for improvement lies in minimizing patient risk of recurrence and long-term sequelae of treatment. Molecular characterization of tumors may provide further information.

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.