Brainstem biopsy in pediatric diffuse intrinsic pontine glioma in the era of precision medicine: the INFORM study experience

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.

H3K27-Altered Diffuse Midline Glioma of the Brainstem: From Molecular Mechanisms to Targeted Interventions

Pediatric high-grade gliomas are a devastating subset of brain tumors, characterized by their aggressive pathophysiology and limited treatment options. Among them, H3 K27-altered diffuse midline gliomas (DMG) of the brainstem stand out due to their distinct molecular features and dismal prognosis. Recent advances in molecular profiling techniques have unveiled the critical role of H3 K27 alterations, particularly a lysine-to-methionine mutation on position 27 (K27M) of the histone H3 tail, in the pathogenesis of DMG. These mutations result in epigenetic dysregulation, which leads to altered chromatin structure and gene expression patterns in DMG tumor cells, ultimately contributing to the aggressive phenotype of DMG. The exploration of targeted therapeutic avenues for DMG has gained momentum in recent years. Therapies, including epigenetic modifiers, kinase inhibitors, and immunotherapies, are under active investigation; these approaches aim to disrupt aberrant signaling cascades and overcome the various mechanisms of therapeutic resistance in DMG. Challenges, including blood-brain barrier penetration and DMG tumor heterogeneity, require innovative approaches to improve drug delivery and personalized treatment strategies. This review aims to provide a comprehensive overview of the evolving understanding of DMG, focusing on the intricate molecular mechanisms driving tumorigenesis/tumor progression and the current landscape of emerging targeted interventions.

A multi-institutional series of a novel, recurrent TRIM24::MET fusion-driven infant-type hemispheric glioma reveals significant clinico-pathological heterogeneity

Within the past decade, incremental integration of molecular characteristics into the classification of central nervous system neoplasms increasingly facilitated precise diagnosis and advanced stratification, beyond potentially providing the foundation for advanced targeted therapies. We report a series of three cases of infant-type hemispheric glioma (IHG) involving three infants diagnosed with neuroepithelial tumors of the cerebral hemispheres harboring a novel, recurrent TRIM24::MET fusion. Histopathology showed glial tumors with either low-grade or high-grade characteristics, while molecular characterization found an additional homozygous CDKN2A/B deletion in two cases. Two patients showed leptomeningeal dissemination, while multiple supra- and infratentorial tumor manifestations were found in one case. Following subtotal resection (two cases) and biopsy (one case), treatment intensity of adjuvant chemotherapy regimens did not reflect in the progression patterns within the reported cases. Two patients showed progression after first-line treatment, of which one patient died not responding to tyrosine kinase inhibitor cabozantinib. As the detection of a recurrent TRIM24::MET fusion expands the spectrum of renowned driving fusion genes in IHG, this comparative illustration may indicate a distinct clinico-pathological heterogeneity of tumors bearing this driver alteration. Upfront clinical trials of IHG promoting further characterization and the implementation of individualized therapies involving receptor tyrosine kinase inhibition are required.

Current status and advances to improving drug delivery in diffuse intrinsic pontine glioma

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma - DIPG), is the primary cause of brain tumor-related death in pediatric patients. DIPG is characterized by a median survival of <12 months from diagnosis, harboring the worst 5-year survival rate of any cancer. Corticosteroids and radiation are the mainstay of therapy; however, they only provide transient relief from the devastating neurological symptoms. Numerous therapies have been investigated for DIPG, but the majority have been unsuccessful in demonstrating a survival benefit beyond radiation alone. Although many barriers hinder brain drug delivery in DIPG, one of the most significant challenges is the blood-brain barrier (BBB). Therapeutic compounds must possess specific properties to enable efficient passage across the BBB. In brain cancer, the BBB is referred to as the blood-brain tumor barrier (BBTB), where tumors disrupt the structure and function of the BBB, which may provide opportunities for drug delivery. However, the biological characteristics of the brainstem's BBB/BBTB, both under normal physiological conditions and in response to DIPG, are poorly understood, which further complicates treatment. Better characterization of the changes that occur in the BBB/BBTB of DIPG patients is essential, as this informs future treatment strategies. Many novel drug delivery technologies have been investigated to bypass or disrupt the BBB/BBTB, including convection enhanced delivery, focused ultrasound, nanoparticle-mediated delivery, and intranasal delivery, all of which are yet to be clinically established for the treatment of DIPG. Herein, we review what is known about the BBB/BBTB and discuss the current status, limitations, and advances of conventional and novel treatments to improving brain drug delivery in DIPG.

Case Report: Low-grade glioma with NF1 loss of function mimicking diffuse intrinsic pontine glioma

Intrinsic, expansile pontine tumors typically occur in the pediatric population. These tumors characteristically present as diffuse intrinsic pontine glioma (DIPG), which is now considered as diffuse midline glioma (DMG), H3K27-mutated of the pons. DIPG has limited treatment options and a poor prognosis, and the value of tissue diagnosis from an invasive biopsy remains controversial. This study presents the case of a 19-year-old female with clinical and imaging hallmarks of DIPG, who underwent a biopsy of a tumor in the region of the right middle cerebellar peduncle. Her lesional cells were negative for H3K27M alterations and had low-grade histologic features. Next-generation sequencing revealed a frameshift mutation in the NF1 gene as the likely driver mutation. These features suggest a diagnosis of a low-grade glioma associated with NF1 loss of function, with far-reaching consequences regarding both treatment strategy and prognosis. This case provides support for the utility of diagnostic tissue biopsy in cases of suspected DIPG.

Stereotactic frame-based biopsy of infratentorial lesions via the suboccipital-transcerebellar approach with the Zamorano-Duchovny stereotactic system-a retrospective analysis of 79 consecutive cases

OBJECTIVE

Lesions of the posterior fossa (brainstem and cerebellum) are challenging in diagnosis and treatment due to the fact that they are often located eloquently and total resection is rarely possible. Therefore, frame-based stereotactic biopsies are commonly used to asservate tissue for neuropathological diagnosis and further treatment determination. The aim of our study was to assess the safety and diagnostic success rate of frame-based stereotactic biopsies for lesions in the posterior fossa via the suboccipital-transcerebellar approach.

METHODS

We performed a retrospective database analysis of all frame-based stereotactic biopsy cases at our institution since 2007. The aim was to identify all surgical cases for infratentorial lesion biopsies via the suboccipital-transcerebellar approach. We collected clinical data regarding outcomes, complications, diagnostic success, radiological appearances, and stereotactic trajectories.

RESULTS

A total of n = 79 cases of stereotactic biopsies for posterior fossa lesions via the suboccipital-transcerebellar approach (41 female and 38 male) utilizing the Zamorano-Duchovny stereotactic system were identified. The mean age at the time of surgery was 42.5 years (± 23.3; range, 1-87 years). All patients were operated with intraoperative stereotactic imaging (n = 62 MRI, n = 17 CT). The absolute diagnostic success rate was 87.3%. The most common diagnoses were glioma, lymphoma, and inflammatory disease. The overall complication rate was 8.7% (seven cases). All patients with complications showed new neurological deficits; of those, three were permanent. Hemorrhage was detected in five of the cases having complications. The 30-day mortality rate was 7.6%, and 1-year survival rate was 70%.

CONCLUSIONS

Our data suggests that frame-based stereotactic biopsies with the Zamorano-Duchovny stereotactic system via the suboccipital-transcerebellar approach are safe and reliable for infratentorial lesions bearing a high diagnostic yield and an acceptable complication rate. Further research should focus on the planning of safe trajectories and a careful case selection with the goal of minimizing complications and maximizing diagnostic success.

Biopsy of diffuse midline glioma is safe and impacts targeted therapy: a systematic review and meta-analysis

PURPOSE

To quantify the safety and utility of biopsy of pediatric diffuse midline glioma (DMG).

METHODS

This study was conducted in accordance with PRISMA guidelines. PubMed, Embase, Scopus, and Web of Science were queried for relevant articles from inception until June 2023. Two reviewers identified all articles that included diagnostic yield, morbidity, and mortality rates for pediatric DMG patients. Studies that did not present original data or were not in English or peer-reviewed were excluded. Meta-analysis was conducted in R using Freeman-Tukey or logit transformation and DerSimonian-Laird random-effects models. The risk of bias was assessed using the Newcastle-Ottawa Scale. A protocol for this review was not registered.

RESULTS

We identified 381 patients from ten studies that met all criteria. DMG biopsy is safe overall (0% mortality, 95% CI: 0-0.6%; 11.0% morbidity, 95% CI: 4.8-18.9%) and has a high diagnostic yield (99.9%, 95% CI: 98.5-100%). The use of stereotactic biopsy is a significant moderator of morbidity (p = 0.0238). Molecular targets can be identified in approximately 53.4% of tumors (95% CI: 37.0-69.0%), although targeted therapies are only delivered in about 33.5% of all cases (95% CI: 24.4-44.1%). Heterogeneity was high for morbidity and identification of targets. The risk of bias was low for all studies.

CONCLUSION

We conducted the first meta-analysis of DMG biopsy to show that it is safe, effective, and able to identify relevant molecular targets that impact targeted therapy.

Molecular-guided therapy for the treatment of patients with relapsed and refractory childhood cancers: a Beat Childhood Cancer Research Consortium trial

BACKGROUND

Children with relapsed central nervous system (CNS tumors), neuroblastoma, sarcomas, and other rare solid tumors face poor outcomes. This prospective clinical trial examined the feasibility of combining genomic and transcriptomic profiling of tumor samples with a molecular tumor board (MTB) approach to make real‑time treatment decisions for children with relapsed/refractory solid tumors.

METHODS

Subjects were divided into three strata: stratum 1-relapsed/refractory neuroblastoma; stratum 2-relapsed/refractory CNS tumors; and stratum 3-relapsed/refractory rare solid tumors. Tumor samples were sent for tumor/normal whole-exome (WES) and tumor whole-transcriptome (WTS) sequencing, and the genomic data were used in a multi-institutional MTB to make real‑time treatment decisions. The MTB recommended plan allowed for a combination of up to 4 agents. Feasibility was measured by time to completion of genomic sequencing, MTB review and initiation of treatment. Response was assessed after every two cycles using Response Evaluation Criteria in Solid Tumors (RECIST). Patient clinical benefit was calculated by the sum of the CR, PR, SD, and NED subjects divided by the sum of complete response (CR), partial response (PR), stable disease (SD), no evidence of disease (NED), and progressive disease (PD) subjects. Grade 3 and higher related and unexpected adverse events (AEs) were tabulated for safety evaluation.

RESULTS

A total of 186 eligible patients were enrolled with 144 evaluable for safety and 124 evaluable for response. The average number of days from biopsy to initiation of the MTB-recommended combination therapy was 38 days. Patient benefit was exhibited in 65% of all subjects, 67% of neuroblastoma subjects, 73% of CNS tumor subjects, and 60% of rare tumor subjects. There was little associated toxicity above that expected for the MGT drugs used during this trial, suggestive of the safety of utilizing this method of selecting combination targeted therapy.

CONCLUSIONS

This trial demonstrated the feasibility, safety, and efficacy of a comprehensive sequencing model to guide personalized therapy for patients with any relapsed/refractory solid malignancy. Personalized therapy was well tolerated, and the clinical benefit rate of 65% in these heavily pretreated populations suggests that this treatment strategy could be an effective option for relapsed and refractory pediatric cancers.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02162732. Prospectively registered on June 11, 2014.

Implementing data on targeted therapy from the INFORM registry platform for children with relapsed cancer in Sweden

Background

Advances in treatment of childhood malignancies have improved overall cure rates to 80%. Nevertheless, cancer is still the most common cause of childhood mortality in Sweden. The prognosis is particularly poor for relapse of high-risk malignancies. In the international INFORM registry, tumor tissue from patients with relapsed, refractory, or progressive pediatric cancer as well as from very-high risk primary tumors is biologically characterized using next-generation sequencing to identify possible therapeutic targets. We analyzed data from Swedish children included in the INFORM registry concerning patient characteristics, survival, sequencing results and whether targeted treatment was administered to the children based on the molecular findings.

Methods

A registry-based descriptive analysis of 184 patients included in the INFORM registry in Sweden during 2016-2021.

Results

The most common diagnoses were soft tissue and bone sarcomas followed by high grade gliomas [including diffuse intrinsic pontine glioma (DIPG)]. Complete molecular analysis was successful for 203/212 samples originating from 184 patients. In 88% of the samples, at least one actionable target was identified. Highly prioritized targets, according to a preset scale, were identified in 48 (24%) samples from 40 patients and 24 of these patients received matched targeted treatment but only six children within a clinical trial. No statistically significant benefit in terms of overall survival or progression free survival was observed between children treated with matched targeted treatment compared to all others.

Conclusion

This international collaborative study demonstrate feasibility regarding sequencing of pediatric high-risk tumors providing molecular data regarding potential actionable targets to clinicians. For a few individuals the INFORM analysis was of utmost importance and should be regarded as a new standard of care with the potential to guide targeted therapy.

Clinical outcomes of stereotactic biopsy on children with pontine diffuse midline glioma

INTRODUCTION

Diffuse midline glioma (DMG) of the pons occurs in pediatric patients and carries a dismal prognosis. Biopsy is not necessary for diagnosis but provides information, particularly H3K27M status, with prognostic implications. Additionally, biopsy information may open therapeutic options such as clinical trials that require mutation status. Therefore, we sought to assess the safety of surgical biopsy in DMG patients as well as its potential impact on clinical course.

METHODS

Retrospective analysis of patients who were radiographically and clinically diagnosed with pontine DMG in the last 5 years was performed. We assessed demographic, clinical, radiographic, surgical, and follow-up data.

RESULTS

25 patients were included; 18 (72%) underwent biopsy while 7 (28%) declined. 12 biopsies (67%) were performed with robotic arm and 5 (27%) with frameless stereotaxy. Three biopsied patients (17%) experienced new post-operative neurologic deficits (1 facial palsy, 1 VI nerve palsy and 1 ataxia) that all resolved at 2-week follow-up. All biopsies yielded diagnostic tissue. Fourteen patients (78%) had H3K27M mutation. Median OS for H3K27M patients was 10 months compared to 11 months in the wild-type patients (p = 0.30, log-rank test). Median OS for patients enrolled in clinical trials was 12 months compared to 8 months for non-trial patients (p = 0.076).

CONCLUSION

In our series, stereotactic pontine DMG biopsies did not carry any permanent deficit or complication and yielded diagnostic tissue in all patients. Similar post-operative course was observed in both robot-assisted and frameless stereotactic approaches. There was no significant difference in survival based on mutation status or clinical trial enrollment.

The molecular diagnostic yield of frame-based stereotactic biopsies in the age of precision neuro-oncology: a cross-sectional study

PURPOSE

With the increasing role of molecular genetics in the diagnostics of intracranial tumors, delivering sufficient representative tissue for such analyses is of paramount importance. This study explored the rate of successful diagnosis after frame-based stereotactic biopsies of intracranial lesions.

METHODS

Consecutive patients undergoing frame-based stereotactic biopsies in 2020 and 2021 were included in this retrospective analysis. Cases were classified into three groups: conclusive, diagnosis with missing molecular genetics (MG) data, and inconclusive neuropathological diagnosis.

RESULTS

Of 145 patients, a conclusive diagnosis was possible in n = 137 cases (94.5%). For 3 cases (2.0%), diagnosis was established with missing MG data. In 5 cases (3.5%), an inconclusive (tumor) diagnosis was met. Diagnoses comprised mainly WHO 4 glioblastomas (n = 73, 56%), CNS lymphomas (n = 23, 16%), inflammatory diseases (n = 14, 10%), and metastases (n = 5, 3%). Methylomics were applied in 49% (n = 44) of tumor cases (panel sequencing in n = 28, 30% of tumors). The average number of specimens used for MG diagnostics was 5, while the average number of specimens provided was 15. In a univariate analysis, insufficient DNA was associated with an inconclusive diagnosis or a diagnosis with missing MG data (p < 0.001). Analyses of planned and implemented trajectories of cases with diagnosis with missing MG data or inconclusive diagnosis (n = 8) revealed that regions of interest were reached in almost all cases (n = 7).

CONCLUSION

Although stereotactic frame-based biopsies deliver a limited amount of tissue, they bear high histopathological and molecular genetic diagnostic yields. Given the proven surgical precision of the planned biopsy trajectories, optimizing surveyed lesion regions could help improve the rate of conclusive diagnoses.

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.

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.

Utility of genome-wide DNA methylation profiling for pediatric-type diffuse gliomas

Despite the current progress of treatment, pediatric-type diffuse glioma is one of the most lethal primary malignant tumors in the central nervous system (CNS). Since pediatric-type CNS tumors are rare disease entities and highly heterogeneous, the diagnosis is challenging. An accurate diagnosis is essential for the choice of optimal treatment, which leads to precision oncology and improvement of the patient's outcome. Genome-wide DNA methylation profiling recently emerged as one of the most important tools for the diagnosis of CNS tumors, and the utility of this novel assay has been reported in both pediatric and adult patients. In the current World Health Organization classification published in 2021, several new entities are recognized in pediatric-type diffuse gliomas, some of which require methylation profiling. In this review, we investigated the utility of genome-wide DNA methylation profiling in pediatric-type diffuse glioma, as well as issues in the clinical application of this assay. Furthermore, the combination of genome-wide DNA methylation profiling and other comprehensive genomic assays, which may improve diagnostic accuracy and detection of the actionable target, will be discussed.

How I treat recurrent pediatric high-grade glioma (pHGG): a Europe-wide survey study

PURPOSE

As there is no standard of care treatment for recurrent/progressing pediatric high-grade gliomas (pHGG), we aimed to gain an overview of different treatment strategies.

METHODS

In a web-based questionnaire, members of the SIOPE-BTG and the GPOH were surveyed on therapeutic options in four case scenarios (children/adolescents with recurrent/progressing HGG).

RESULTS

139 clinicians with experience in pediatric neuro-oncology from 22 European countries participated in the survey. Most respondents preferred further oncological treatment in three out of four cases and chose palliative care in one case with marked symptoms. Depending on the case, 8-92% would initiate a re-resection (preferably hemispheric pHGG), combined with molecular diagnostics. Throughout all case scenarios, 55-77% recommended (re-)irradiation, preferably local radiotherapy > 20 Gy. Most respondents would participate in clinical trials and use targeted therapy (79-99%), depending on molecular genetic findings (BRAF alterations: BRAF/MEK inhibitor, 64-88%; EGFR overexpression: anti-EGFR treatment, 46%; CDKN2A deletion: CDK inhibitor, 18%; SMARCB1 deletion: EZH2 inhibitor, 12%). 31-72% would administer chemotherapy (CCNU, 17%; PCV, 8%; temozolomide, 19%; oral etoposide/trofosfamide, 8%), and 20-69% proposed immunotherapy (checkpoint inhibitors, 30%; tumor vaccines, 16%). Depending on the individual case, respondents would also include bevacizumab (6-18%), HDAC inhibitors (4-15%), tumor-treating fields (1-26%), and intraventricular chemotherapy (4-24%).

CONCLUSION

In each case, experts would combine conventional multimodal treatment concepts, including re-irradiation, with targeted therapy based on molecular genetic findings. International cooperative trials combining a (chemo-)therapy backbone with targeted therapy approaches for defined subgroups may help to gain valid clinical data and improve treatment in pediatric patients with recurrent/progressing HGG.

Real-time drug testing of paediatric diffuse midline glioma to support clinical decision making: The Zurich DIPG/DMG centre experience

BACKGROUND

Children diagnosed with diffuse midline gliomas (DMG) have an extremely poor overall survival: 9-12 months from diagnosis with currently no curative treatment options. Given DMG molecular heterogeneity, surgical biopsies are needed for molecular profiling and as part of enrolment into molecular-based and precision medicine type clinical interventions. In this study, we describe the results of real time profiling and drug testing at the diffuse intrinsic pontine glioma/DMG Research Centre at University Children's Hospital Zurich.

METHOD

Biopsies were taken using a frame based stereotactic robot system (NeuroMate®, Renishaw) at University Children's Hospital Zurich. Tissue samples were evaluated to confirm diagnosis by H3K27M and H3K27 trimethylation loss. Genomic analyses were done using a variety of platforms (INFORM, Oncomine, UCSF500 gene panel). Cell lines were developed by mechanical tissue dissociation and verified by either sequencing or immunofluorescence staining confirming H3K27M mutation and used afterwards for drug testing.

RESULTS

Twenty-five robot-assisted primary biopsies were successfully performed. Median hospital stay was 2 days (range 1-4 days). Nine low-passage patient-derived cells were developed, whereas 8 cell lines were used to inform response to clinically relevant drugs. Genome and RNA expression were used to further guide treatment strategies with targeted agents such as dual PI3K/mTOR inhibitor paxalisib.

CONCLUSION

We established a systematic workflow for safe, robot-assisted brainstem biopsies and in-house tissue processing, followed by real-time drug testing. This provides valuable insights into tumour prognostic and individual treatment strategies targeting relevant vulnerabilities in these tumours in a clinically meaningful time frame.

Frameless Robotic-Assisted Biopsy of Pediatric Brainstem Lesions: A Systematic Review and Meta-Analysis of Efficacy and Safety

BACKGROUND

Pediatric brainstem lesions are diagnoses that require tissue sampling to advance our understanding of them and their management. Frameless, robot-assisted biopsy of these lesions has emerged as a novel, viable biopsy approach. Correspondingly, the aim of this study was to quantitively and qualitatively summarize the contemporary literature regarding the likelihood of achieving tumor diagnosis and experiencing any postoperative complications.

METHODS

Searches of 7 electronic databases from inception to September 2022 were conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles were screened against prespecified criteria. Outcomes were pooled by random-effects meta-analyses of proportions where possible.

RESULTS

A total of 8 cohort studies satisfied all criteria. They described 99 pediatric patients with brainstem lesions in whom frameless, robot-assisted biopsy was involved in their work-up. There were 62 (63%) male and 37 (37%) female patients with a median age of 9 years at time of biopsy. Overall, all patients had sufficient tissue obtained by initial biopsy for evaluation. Pooled estimate of achieving tumor diagnosis was 100% (95% confidence interval [CI] 97%-100%) across all studies with a high degree of certainty. Across all studies, there were no cases of procedure-related mortality. The pooled estimates of transient and permanent complications after biopsy were 10% (95% CI 4%-19%) and 0% (95% CI 0%-2%), respectively, of very low and low degrees of certainty each.

CONCLUSIONS

The contemporary metadata demonstrates the frameless, robot-assisted biopsy of pediatric brainstem lesions is both effective and safe when performed in an experienced setting. Further research is needed to augment robot and automated technologies into workup algorithms.

Interdisciplinary care of children with diffuse midline glioma

Diffuse Midline Glioma (DMG) which includes Diffuse Intrinsic Pontine Glioma (DIPG) is an infiltrative tumor of the midline structures of the central nervous system that demonstrates an aggressive pattern of growth and has no known curative treatment. As these tumors progress, children experience ongoing neurological decline including inability to ambulate, swallow and communicate effectively. We propose that optimal care for patients with DMG should involve a specialized team experienced in caring for the multifaceted needs of these patients and their families. Herein we review the roles and evidence to support early involvement of a specialized interdisciplinary team and outline our views on best practices for these challenging tumors.

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.

Roles and outcomes of stereotactic biopsy for adult patients with brainstem lesion

PURPOSE

This study aimed to assess the benefit-risk ratio by determining diagnostic yield and safety of brainstem biopsies in adult patients. The secondary objectives were (i) to compare brainstem biopsy safety and postbiopsy patients' outcomes and survival with those of patients biopsied for a brain or cerebellar lesion, and (ii) to assess the impact of brainstem biopsy on final diagnosis and further therapeutic management.

METHODS

Among 1784 stereotactic biopsies performed in adult patients at a tertiary center between April 2009 and October 2020, we retrospectively examined 50 consecutive brainstem biopsies. We compared variables regarding diagnostic yield, safety and post-biopsy outcomes between brainstem biopsy patients and brain/cerebellum biopsy patients.

RESULTS

Brainstem biopsy led to a diagnosis in 86% of patients (94.6% in patients with suspected tumor). Lesion contrast enhancement on imaging was the sole predictor of obtaining a diagnosis. Rates of symptomatic complications and mortality were significantly higher in brainstem biopsy patients compared to brain/cerebellum biopsy patients (20% vs 0%; p < 0.001 and 6% vs 0%; p = 0.01, respectively). Transfrontal trajectory and prebiopsy swallowing disorders were predictors of brainstem biopsy-related symptomatic complications. Brainstem biopsy findings led to diagnostic change in 22% of patients.

CONCLUSIONS

Stereotactic biopsy in adult patients with brainstem lesion has a high diagnostic yield. Although stereotactic brainstem biopsy is associated with more functional and fatal complications than biopsies targeting the brain/cerebellum, its safety profile appears acceptable. Thus, the benefit-risk ratio of stereotactic biopsy in patients with brainstem lesion is favorable but should nevertheless be carefully weighted on a case-by-case basis.

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.

A tumor suppressor role for EZH2 in diffuse midline glioma pathogenesis

Pediatric high-grade gliomas, specifically diffuse midline gliomas, account for only 20% of clinical cases but are 100% fatal. A majority of the DMG cases are characterized by the signature K27M mutation in histone H3. The H3K27M mutation opposes the function of enhancer of zeste homolog 2 (EZH2), the methyltransferase enzyme of the polycomb repressor complex 2. However, the role of EZH2 in DMG pathogenesis is unclear. In this study, we demonstrate a tumor suppressor function for EZH2 using Ezh2 loss- and gain-of-function studies in H3WT DMG mouse models. Genetic ablation of Ezh2 increased cell proliferation and tumor grade while expression of an Ezh2 gain-of-function mutation significantly reduced tumor incidence and increased tumor latency. Transcriptomic analysis revealed that Ezh2 deletion upregulates an inflammatory response with upregulation of immunoproteasome genes such as Psmb8, Psmb9, and Psmb10. Ezh2 gain-of-function resulted in enrichment of the oxidative phosphorylation/mitochondrial metabolic pathway namely the isocitrate dehydrogenase Idh1/2/3 genes. Pharmacological inhibition of EZH2 augmented neural progenitor cell proliferation, supporting the tumor suppressive role of EZH2. In vivo 7-day treatment of H3K27M DMG tumor bearing mice with an EZH2 inhibitor, Tazemetostat, did not alter proliferation or significantly impact survival. Together our results suggest that EZH2 has a tumor suppressor function in DMG and warrants caution in clinical translation of EZH2 inhibitors to treat patients with DMG.

Phase I study using crenolanib to target PDGFR kinase in children and young adults with newly diagnosed DIPG or recurrent high-grade glioma, including DIPG

Background

Platelet-derived growth factor receptor (PDGFR) signaling has been directly implicated in pediatric high-grade gliomagenesis. This study evaluated the safety and tolerability of crenolanib, a potent, selective inhibitor of PDGFR-mediated phosphorylation, in pediatric patients with high-grade glioma (HGG).

Methods

We used a rolling-6 design to study the maximum tolerated dose (MTD) of once-daily crenolanib administered during and after focal radiation therapy in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG) (stratum A) or with recurrent/progressive HGG (stratum B). Pharmacokinetics were studied during the first cycle at the first dose and at steady state (day 28). Alterations in PDGFRA were assessed by Sanger or exome sequencing and interphase fluorescence in situ hybridization or single nucleotide polymorphism arrays.

Results

Fifty evaluable patients were enrolled in the 2 strata, and an MTD of 170 mg/m² was established for both. Dose-limiting toxicities were primarily liver enzyme elevations and hematologic count suppression in both strata. Crenolanib AUC_0-48h and C _MAX did not differ significantly for crushed versus whole-tablet administration. Overall, PDGFRA alterations were observed in 25% and 30% of patients in stratum A and B, respectively. Neither crenolanib therapy duration nor survival outcomes differed significantly by PDGFRA status, and overall survival of stratum A was similar to that of historical controls.

Conclusions

Children tolerate crenolanib well at doses slightly higher than the established MTD in adults, with a toxicity spectrum generally similar to that in adults. Studies evaluating intratumoral PDGFR pathway inhibition in biomarker-enriched patients are needed to evaluate further the clinical utility of crenolanib in this population.

Liquid biopsy in gliomas: A RANO review and proposals for clinical applications

BACKGROUND

There is an extensive literature highlighting the utility of blood-based liquid biopsies in several extracranial tumors for diagnosis and monitoring.

METHODS

The RANO (Response Assessment in Neuro-Oncology) group developed a multidisciplinary international Task Force to review the English literature on liquid biopsy in gliomas focusing on the most frequently used techniques, that is circulating tumor DNA, circulating tumor cells, and extracellular vesicles in blood and CSF.

RESULTS

ctDNA has a higher sensitivity and capacity to represent the spatial and temporal heterogeneity in comparison to circulating tumor cells. Exosomes have the advantages to cross an intact blood-brain barrier and carry also RNA, miRNA, and proteins. Several clinical applications of liquid biopsies are suggested: to establish a diagnosis when tissue is not available, monitor the residual disease after surgery, distinguish progression from pseudoprogression, and predict the outcome.

CONCLUSIONS

There is a need for standardization of biofluid collection, choice of an analyte, and detection strategies along with rigorous testing in future clinical trials to validate findings and enable entry into clinical practice.

iTReX: Interactive exploration of mono- and combination therapy dose response profiling data

High throughput screening methods, measuring the sensitivity and resistance of tumor cells to drug treatments have been rapidly evolving. Not only do these screens allow correlating response profiles to tumor genomic features for developing novel predictors of treatment response, but they can also add evidence for therapy decision making in precision oncology. Recent analysis methods developed for either assessing single agents or combination drug efficacies enable quantification of dose-response curves with restricted symmetric fit settings. Here, we introduce iTReX, a user-friendly and interactive Shiny/R application, for both the analysis of mono- and combination therapy responses. The application features an extended version of the drug sensitivity score (DSS) based on the integral of an advanced five-parameter dose-response curve model and a differential DSS for combination therapy profiling. Additionally, iTReX includes modules that visualize drug target interaction networks and support the detection of matches between top therapy hits and the sample omics features to enable the identification of druggable targets and biomarkers. iTReX enables the analysis of various quantitative drug or therapy response readouts (e.g. luminescence, fluorescence microscopy) and multiple treatment strategies (drug treatments, radiation). Using iTReX we validate a cost-effective drug combination screening approach and reveal the application's ability to identify potential sample-specific biomarkers based on drug target interaction networks. The iTReX web application is accessible at https://itrex.kitz-heidelberg.de.

Pharmaco-proteogenomic profiling of pediatric diffuse midline glioma to inform future treatment strategies

Diffuse midline glioma (DMG) is a deadly pediatric and adolescent central nervous system (CNS) tumor localized along the midline structures of the brain atop the spinal cord. With a median overall survival (OS) of just 9–11-months, DMG is characterized by global hypomethylation of histone H3 at lysine 27 (H3K27me3), driven by recurring somatic mutations in H3 genes including, HIST1H3B/C (H3.1K27M) or H3F3A (H3.3K27M), or through overexpression of EZHIP in patients harboring wildtype H3. The recent World Health Organization’s 5th Classification of CNS Tumors now designates DMG as, ‘H3 K27-altered’, suggesting that global H3K27me3 hypomethylation is a ubiquitous feature of DMG and drives devastating transcriptional programs for which there are no treatments. H3-alterations co-segregate with various other somatic driver mutations, highlighting the high-level of intertumoral heterogeneity of DMG. Furthermore, DMG is also characterized by very high-level intratumoral diversity with tumors harboring multiple subclones within each primary tumor. Each subclone contains their own combinations of driver and passenger lesions that continually evolve, making precision-based medicine challenging to successful execute. Whilst the intertumoral heterogeneity of DMG has been extensively investigated, this is yet to translate to an increase in patient survival. Conversely, our understanding of the non-genomic factors that drive the rapid growth and fatal nature of DMG, including endogenous and exogenous microenvironmental influences, neurological cues, and the posttranscriptional and posttranslational architecture of DMG remains enigmatic or at best, immature. However, these factors are likely to play a significant role in the complex biological sequelae that drives the disease. Here we summarize the heterogeneity of DMG and emphasize how analysis of the posttranslational architecture may improve treatment paradigms. We describe factors that contribute to treatment response and disease progression, as well as highlight the potential for pharmaco-proteogenomics (i.e., the integration of genomics, proteomics and pharmacology) in the management of this uniformly fatal cancer.

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

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

Progress in diffuse intrinsic pontine glioma: advocating for stereotactic biopsy in the standard of care

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal pediatric brainstem tumor affecting approximately 300 children in the US annually. Median survival is less than 1 year, and radiation therapy has been the mainstay of treatment for decades. Recent advances in the biological understanding of the disease have identified the H3K27M mutation in nearly 80% of DIPGs, leading to the 2016 WHO classification of diffuse midline glioma H3K27M-mutant, a grade IV brainstem tumor. Developments in epigenetic targeting of transcriptional tendencies have yielded potential molecular targets for clinical trials. Chimeric antigen receptor T cell therapy has also shown preclinical promise. Recent clinical studies, including prospective trials, have demonstrated the safety and feasibility of pediatric brainstem biopsy in the setting of DIPG and other brainstem tumors. Given developments in the ability to analyze DIPG tumor tissue to deepen biological understanding of this disease and develop new therapies for treatment, together with the increased safety of stereotactic brainstem biopsy, the authors present a case for offering biopsy to all children with suspected DIPG. They also present their standard operative techniques for image-guided, frameless stereotactic biopsy.

Pediatric Glioma: An Update of Diagnosis, Biology, and Treatment

Simple Summary

Recent research has enhanced our understanding of the diverse biological processes that occur in pediatric gliomas; and molecular genetic analysis has become essential to diagnose and treat these conditions. Because targetable molecular aberrations can be detected in pediatric gliomas, identifying these aberrations is very important. This review provides an overview of pediatric gliomas, and describes recent developments made in strategies for their diagnosis and treatment. Additionally, it presents a current picture of pediatric gliomas in light of advances in molecular genetics, and describes the current scientific progress in gliomas’ treatment using information from recently completed and ongoing clinical trials. The era of incorporating molecular genetic analysis into clinical practice is emerging.

Abstract

Recent research has promoted elucidation of the diverse biological processes that occur in pediatric central nervous system (CNS) tumors. Molecular genetic analysis is essential not only for proper classification, but also for monitoring biological behavior and clinical management of tumors. Ever since the 2016 World Health Organization classification of CNS tumors, molecular profiling has become an indispensable step in the diagnosis, prediction of prognosis, and treatment of pediatric as well as adult CNS tumors. These molecular data are changing diagnosis, leading to new guidelines, and offering novel molecular targeted therapies. The Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW) makes practical recommendations using recent advances in CNS tumor classification, particularly in molecular discernment of these neoplasms as morphology-based classification of tumors is being replaced by molecular-based classification. In this article, we summarize recent knowledge to provide an overview of pediatric gliomas, which are major pediatric CNS tumors, and describe recent developments in strategies employed for their diagnosis and treatment.

Magnetic resonance imaging of the brainstem in children, part 2: acquired pathology of the pediatric brainstem

Part 1 of this series of two articles describes conventional and advanced MRI techniques that are useful for evaluating brainstem pathologies. In addition, it provides a review of the embryology, normal progression of myelination, and clinically and radiologically salient imaging anatomy of the normal brainstem. Finally, it discusses congenital diseases of the brainstem with a focus on distinctive imaging features that allow for differentiating pathologies. Part 2 of this series of two articles includes discussion of neoplasms; infections; and vascular, demyelinating, toxic, metabolic and miscellaneous disease processes affecting the brainstem. The ultimate goal of this pair of articles is to empower the radiologist to add clinical value in the care of pediatric patients with brainstem pathologies.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

MRI-based diagnosis and treatment of pediatric brain tumors: is tissue sample always needed?

Traditional management of newly diagnosed pediatric brain tumors (PBTs) consists of cranial imaging, typically magnetic resonance imaging (MRI), and is frequently followed by tissue diagnosis, through either surgical biopsy or tumor resection. Therapy regimes are typically dependent on histological diagnosis. To date, many treatment regimens are based on molecular biology. The scope of this article is to discuss the role of diagnosis and further treatment of PBTs based solely on MRI features, in light of the latest treatment protocols. Typical MRI findings and indications for surgical biopsy of these lesions are described.

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.

Cerebrospinal Fluid Penetration and Combination Therapy of Entrectinib for Disseminated ROS1/NTRK-Fusion Positive Pediatric High-Grade Glioma

Targeting oncogenic fusion-genes in pediatric high-grade gliomas (pHGG) with entrectinib has emerged as a highly promising therapeutic approach. Despite ongoing clinical studies, to date, no reports on the treatment of cerebrospinal fluid (CSF) disseminated fusion-positive pHGG exist. Moreover, clinically important information of combination with other treatment modalities such as intrathecal therapy, radiotherapy and other targeted agents is missing. We report on our clinical experience of entrectinib therapy in two CSF disseminated ROS1/NTRK-fusion-positive pHGG cases. Combination of entrectinib with radiotherapy or intrathecal chemotherapy appears to be safe and has the potential to act synergistically with entrectinib treatment. In addition, we demonstrate CSF penetrance of entrectinib for the first time in patient samples suggesting target engagement even upon CSF dissemination. Moreover, in vitro analyses of two novel cell models derived from one case with NTRK-fusion revealed that combination therapy with either a MEK (trametinib) or a CDK4/6 (abemaciclib) inhibitor synergistically enhances entrectinib anticancer effects. In summary, our comprehensive study, including clinical experience, CSF penetrance and in vitro data on entrectinib therapy of NTRK/ROS1-fusion-positive pHGG, provides essential clinical and preclinical insights into the multimodal treatment of these highly aggressive tumors. Our data suggest that combined inhibition of NTRK/ROS1 and other therapeutic vulnerabilities enhances the antitumor effect, which should be followed-up in further preclinical and clinical studies.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Improving long-term survival in diffuse intrinsic pontine glioma

INTRODUCTION

Diffuse intrinsic pontine glioma (DIPG) is an almost universally fatal pediatric brain cancer. There has been no improvement in event-free survival (EFS) or overall survival (OS) despite immense effort through a multitude of clinical trials to find a cure. Recently, there has been a surge in the knowledge of DIPG biology, including the discovery of a recurrent H3F3A mutation in over 80% of these tumors.

AREAS COVERED

The authors review the most recent approaches to diagnosis and treatment of DIPG including chemotherapy, biologics, surgical approaches, and immunotherapy.

EXPERT OPINION

The authors propose four main opportunities to improve long-term survival. First, patients should be enrolled in scientifically sound clinical trials that include molecularly profiling either via stereotactic biopsy or liquid biopsy. Second, clinical trials should include more innovative endpoints other than traditional EFS and OS such as MRI/PET imaging findings combined with surrogates of activity (e.g. serial liquid biopsies) to better ascertain biologically active treatments. Third, innovative clinical trial approaches are needed to help allow for the rapid development of combination therapies to be tested. Finally, effort should be concentrated on reversing the effects of the histone mutation, as this malfunctioning development program seems to be key to DIPG relentlessness.

INFORM2 NivEnt: The first trial of the INFORM2 biomarker driven phase I/II trial series: the combination of nivolumab and entinostat in children and adolescents with refractory high-risk malignancies

Background

Pediatric patients with relapsed or refractory disease represent a population with a desperate medical need. The aim of the INFORM (INdividualized Therapy FOr Relapsed Malignancies in Childhood) program is to translate next generation molecular diagnostics into a biomarker driven treatment strategy. The program consists of two major foundations: the INFORM registry providing a molecular screening platform and the INFORM2 series of biomarker driven phase I/II trials. The INFORM2 NivEnt trial aims to determine the recommended phase 2 dose (RP2D) of the combination treatment of nivolumab and entinostat (phase I) and to evaluate activity and safety (phase II).

Methods

This is an exploratory non-randomized, open-label, multinational and multicenter seamless phase I/II trial in children and adolescents with relapsed / refractory or progressive high-risk solid tumors and CNS tumors. The phase I is divided in 2 age cohorts: 12–21 years and 6–11 years and follows a 3 + 3 design with two dose levels for entinostat (2 mg/m² and 4 mg/m² once per week) and fixed dose nivolumab (3 mg/kg every 2 weeks). Patients entering the trial on RP2D can seamlessly enter phase II which consists of a biomarker defined four group basket trial: high mutational load (group A), high PD-L1 mRNA expression (group B), focal MYC(N) amplification (group C), low mutational load and low PD-L1 mRNA expression and no MYC(N) amplification (group D). A Bayesian adaptive design will be used to early stop cohorts that fail to show evidence of activity. The maximum number of patients is 128.

Discussion

This trial intends to exploit the immune enhancing effects of entinostat on nivolumab using an innovative biomarker driven approach in order to maximize the chance of detecting signs of activity. It prevents exposure to unnecessary risks by applying the Bayesian adaptive design for early stopping for futility. The adaptive biomarker driven design provides an innovative approach accelerating drug development and reducing exposure to investigational treatments in these vulnerable children at the same time.

Trial registration

ClinicalTrials.gov, NCT03838042. Registered on 12 February 2019.

Addition of Multimodal Immunotherapy to Combination Treatment Strategies for Children with DIPG: A Single Institution Experience

Background: The prognosis of children with diffuse intrinsic pontine glioma (DIPG) remains dismal despite radio- and chemotherapy or molecular-targeted therapy. Immunotherapy is a powerful and promising approach for improving the overall survival (OS) of children with DIPG. Methods: A retrospective analysis for feasibility, immune responsiveness, and OS was performed on 41 children treated in compassionate use with multimodal therapy consisting of Newcastle disease virus, hyperthermia, and autologous dendritic cell vaccines as part of an individualized combinatorial treatment approach for DIPG patients. Results: Patients were treated at diagnosis (n = 28) or at the time of progression (n = 13). In the case of 16 patients, histone H3K27M mutation was confirmed by analysis of biopsy (n = 9) or liquid biopsy (n = 9) specimens. PDL1 mRNA expression was detected in circulating tumor cells of ten patients at diagnosis. Multimodal immunotherapy was feasible as scheduled, until progression, in all patients without major toxicity. When immunotherapy was part of primary treatment, median PFS and OS were 8.4 m and 14.4 m from the time of diagnosis, respectively, with a 2-year OS of 10.7%. When immunotherapy was given at the time of progression, median PFS and OS were 6.5 m and 9.1 m, respectively. A longer OS was associated with a Th1 shift and rise in PanTum Detect test scores. Conclusions: Multimodal immunotherapy is feasible without major toxicity, and warrants further investigation as part of a combinatorial treatment approach for children diagnosed with DIPG.

Clinical, imaging, and molecular analysis of pediatric pontine tumors lacking characteristic imaging features of DIPG

Diffuse intrinsic pontine glioma (DIPG) is most commonly diagnosed based on imaging criteria, with biopsy often reserved for pontine tumors with imaging features not typical for DIPG (atypical DIPG, 'aDIPG'). The histopathologic and molecular spectra of the clinical entity aDIPG remain to be studied systematically. In this study, thirty-three patients with newly diagnosed pontine-centered tumors with imaging inconsistent with DIPG for whom a pathologic diagnosis was subsequently obtained were included. Neoplasms were characterized by routine histology, immunohistochemistry, interphase fluorescence in situ hybridization, Sanger and next-generation DNA/RNA sequencing, and genome-wide DNA methylome profiling. Clinicopathologic features and survival outcomes were analyzed and compared to those of a contemporary cohort with imaging features consistent with DIPG (typical DIPG, 'tDIPG'). Blinded retrospective neuroimaging review assessed the consistency of the initial imaging-based diagnosis and correlation with histopathology. WHO grade II-IV infiltrating gliomas were observed in 54.6% of the cases; the remaining were low-grade gliomas/glioneuronal tumors or CNS embryonal tumors. Histone H3 K27M mutation, identified in 36% of the cases, was the major prognostic determinant. H3 K27M-mutant aDIPG and H3 K27M-mutant tDIPG had similar methylome profiles but clustered separately from diffuse midline gliomas of the diencephalon and spinal cord. In the aDIPG cohort, clinicoradiographic features did not differ by H3 status, yet significant differences in clinical and imaging features were observed between aDIPG without H3 K27M mutation and tDIPG. Neuroimaging review revealed discordance between the classification of aDIPG and tDIPG and did not correlate with the histology of glial/glioneuronal tumors or tumor grade. One patient (3.1%) developed persistent neurologic deficits after surgery; there were no surgery-related deaths. Our study demonstrates that surgical sampling of aDIPG is well-tolerated and provides significant diagnostic, therapeutic, and prognostic implications, and that neuroimaging alone is insufficient to distinguish aDIPG from tDIPG. H3 K27M-mutant aDIPG is epigenetically and clinically similar to H3 K27M-mutant tDIPG.

Biopsy in diffuse pontine gliomas: expert neurosurgeon opinion-a survey from the SIOPE brain tumor group

INTRODUCTION

The prognosis of diffuse intrinsic pontine glioma (DIPG) is poor. The role of biopsy in DIPG remains controversial since the diagnosis may be established with imaging alone. Recent advances in understanding molecular biology and targeting of brain tumors have created a renewed interest in biopsy for DIPG. The Neurosurgery Working Group (NWG) of the SIOP-Europe Brain Tumor Group (BTG) undertook a survey among international pediatric neurosurgeons to define their current perceptions and practice regarding DIPG biopsy.

METHODS

The NWG developed a 20-question survey which was emailed to neurosurgeons in the International Society for Pediatric Neurosurgery (ISPN). The questionnaire included questions on diagnosis, indications, and techniques for biopsy, clinical trials, and healthcare infrastructure.

RESULTS

The survey was sent to 202 neurosurgeons and 73 (36%) responded. Consensus of > 75% agreement was reached for 12/20 questions, which included (1) radiological diagnosis of DIPG is sufficient outside a trial, (2) clinical trial-based DIPG biopsy is justified if molecular targets are investigated and may be used for treatment, and (3) morbidity/mortality data must be collected to define the risk:benefit ratio. The remaining 8/20 questions proved controversial and failed to reach consensus.

CONCLUSIONS

Routine DIPG biopsy continues to be debated. Most neurosurgeons agreed that DIPG biopsy within a clinical trial should be supported, with the aims of defining the procedure risks, improving understanding of tumor biology, and evaluating new treatment targets. Careful family counseling and consent remain important.

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.

Personalized Treatment of H3K27M-Mutant Pediatric Diffuse Gliomas Provides Improved Therapeutic Opportunities

Diffuse gliomas with K27M histone mutations (H3K27M glioma) are generally characterized by a fatal prognosis, particularly affecting the pediatric population. Based on the molecular heterogeneity observed in this tumor type, personalized treatment is considered to substantially improve therapeutic options. Therefore, clinical evidence for therapy, guided by comprehensive molecular profiling, is urgently required. In this study, we analyzed feasibility and clinical outcomes in a cohort of 12 H3K27M glioma cases treated at two centers. Patients were subjected to personalized treatment either at primary diagnosis or disease progression and received backbone therapy including focal irradiation. Molecular analyses included whole-exome sequencing of tumor and germline DNA, RNA-sequencing, and transcriptomic profiling. Patients were monitored with regular clinical as well as radiological follow-up. In one case, liquid biopsy of cerebrospinal fluid (CSF) was used. Analyses could be completed in 83% (10/12) and subsequent personalized treatment for one or more additional pharmacological therapies could be recommended in 90% (9/10). Personalized treatment included inhibition of the PI3K/AKT/mTOR pathway (3/9), MAPK signaling (2/9), immunotherapy (2/9), receptor tyrosine kinase inhibition (2/9), and retinoic receptor agonist (1/9). The overall response rate within the cohort was 78% (7/9) including one complete remission, three partial responses, and three stable diseases. Sustained responses lasting for 28 to 150 weeks were observed for cases with PIK3CA mutations treated with either miltefosine or everolimus and additional treatment with trametinib/dabrafenib in a case with BRAFV600E mutation. Immune checkpoint inhibitor treatment of a case with increased tumor mutational burden (TMB) resulted in complete remission lasting 40 weeks. Median time to progression was 29 weeks. Median overall survival (OS) in the personalized treatment cohort was 16.5 months. Last, we compared OS to a control cohort (n = 9) showing a median OS of 17.5 months. No significant difference between the cohorts could be detected, but long-term survivors (>2 years) were only present in the personalized treatment cohort. Taken together, we present the first evidence of clinical efficacy and an improved patient outcome through a personalized approach at least in selected cases of H3K27M glioma.

The Promise and the Reality of Genomics to Guide Precision Medicine in Pediatric Oncology: The Decade Ahead

Much has been written about the promise of "precision medicine," especially in oncology, where somatic mutations can influence the response of cancer cells to "targeted therapy." There have been successful examples of targeted therapy improving the outcome of some childhood cancers, such as the addition of an ABL class tyrosine kinase inhibitor to conventional chemotherapy substantially improving the cure rate for patients with BCR-ABL1 positive acute lymphoblastic leukemia. Although there are other mutations serving as putative targets in various childhood leukemias and solid tumors, effective targeted therapy has yet to be established for them in prospective clinical trials. There are also uncertainties about which "targeted therapy" to use when patients have multiple targetable genomic lesions in their cancer cells, given the paucity of data upon which to develop evidence-based guidelines for selecting and integrating targeted agents for individual patients. There are also multiple examples of inherited germline variants for which evidence-based guidelines have been developed by the Clinical Pharmacogenetics Implementation Consortium to guide the selection and dosing of medications in children with cancer. Clinical pharmacology is poised to play a critical role in both the discovery and development of new targeted anticancer agents and their evidence-based translation into better treatment for children with cancer. To embrace these challenges and opportunities of "precision medicine," clinical and basic pharmacologists must expand the depth of our science and the bandwidth of our translational capacity if we are to optimize precision medicine and advance the treatment of cancer in children and adults.

Liquid biopsy for pediatric diffuse midline glioma: a review of circulating tumor DNA and cerebrospinal fluid tumor DNA

Diffuse midline glioma (DMG) is a highly malignant childhood tumor with an exceedingly poor prognosis and limited treatment options. The majority of these tumors harbor somatic mutations in genes encoding histone variants. These recurrent mutations correlate with treatment response and are forming the basis for molecularly guided clinical trials. The ability to detect these mutations, either in circulating tumor DNA (ctDNA) or cerebrospinal fluid tumor DNA (CSF-tDNA), may enable noninvasive molecular profiling and earlier prediction of treatment response. Here, the authors review ctDNA and CSF-tDNA detection methods, detail recent studies that have explored detection of ctDNA and CSF-tDNA in patients with DMG, and discuss the implications of liquid biopsies for patients with DMG.

Liquid biopsy for diffuse intrinsic pontine glioma: an update

Diffuse intrinsic pontine glioma (DIPG), otherwise known as diffuse midline glioma with H3K27M mutation, is a devastating brainstem glioma without a cure. Efforts are currently underway to better optimize molecular diagnoses through biological sampling, which today remains largely limited to surgical biopsy sampling. Surgical intervention is not without its risks, and therefore a preference remains for a less invasive modality that can provide biological information about the tumor. There is emerging evidence to suggest that a liquid biopsy, targeting biofluids such as CSF and blood plasma, presents an attractive alternative for brain tumors in general. In this update, the authors provide a summary of the progress made to date regarding the use of liquid biopsy to diagnose and monitor DIPG, and they also propose future development and applications of this technique moving forward, given its unique histone biology.