Diffuse Intrinsic Pontine Glioma: Time for Cautious Optimism

Management of patients with diffuse intrinsic pontine glioma in Australia and New Zealand: Australian and New Zealand Children's Haematology/Oncology Group position statement

INTRODUCTION

The main mission of the Australian and New Zealand Children's Haematology and Oncology Group (ANZCHOG) is to develop and facilitate local access to the world's leading evidence-based clinical trials for all paediatric cancers, including brain tumours, as soon as practically possible. Diffuse intrinsic pontine gliomas (DIPGs) - a subset of a larger group of tumours now termed diffuse midline glioma, H3K27-altered (DMG) - are paediatric brain cancers with less than 10% survival at two years. In the absence of any proven curative therapies, significant recent advancements have been made in pre-clinical and clinical research, leading many to seek integration of novel therapies early into standard practice. Despite these innovative therapeutic approaches, DIPG remains an incurable disease for which novel surgical, imaging, diagnostic, radiation and systemic therapy approaches are needed.

MAIN RECOMMENDATIONS

All patients with DIPG should be discussed in multidisciplinary neuro-oncology meetings (including pathologists, neuroradiologists, radiation oncologists, neurosurgeons, medical oncologists) at diagnosis and at relapse or progression. Radiation therapy to the involved field remains the local and international standard of care treatment. Proton therapy does not yield a superior survival outcome compared with photon therapy and patients should undergo radiation therapy with the available modality (photon or proton) at their treatment centre. Patients may receive concurrent chemotherapy or radiation-sensitising agents as part of a clinical trial. Biopsy should be offered to facilitate consideration of experimental therapies and eligibility for clinical trial participation. After radiation therapy, each patient should be managed individually with either observation or considered for enrolment on a clinical trial, if eligible, after full discussion with the family. Re-irradiation can be considered for progressive disease.

CHANGES IN MANAGEMENT AS A RESULT OF THE GUIDELINE

Every child diagnosed with DIPG should be offered enrolment on a clinical trial where available. Access to investigational drugs without biological rationale outside the clinical trial setting is not supported. In case of potentially actionable target identification with molecular profiling and absence of a suitable clinical trial, rational targeted therapies can be considered through compassionate access programs.

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.

Biological functions of the Olig gene family in brain cancer and therapeutic targeting

The Olig genes encode members of the basic helix-loop-helix (bHLH) family of transcription factors. Olig1, Olig2, and Olig3 are expressed in both the developing and mature central nervous system (CNS) and regulate cellular specification and differentiation. Over the past decade extensive studies have established functional roles of Olig1 and Olig2 in development as well as in cancer. Olig2 overexpression drives glioma proliferation and resistance to radiation and chemotherapy. In this review, we summarize the biological functions of the Olig family in brain cancer and how targeting Olig family genes may have therapeutic benefit.

Addressing blood-brain-tumor-barrier heterogeneity in pediatric brain tumors with innovative preclinical models

Brain tumors represent the leading cause of disease-related mortality and morbidity in children, with effective treatments urgently required. One factor limiting the effectiveness of systemic therapy is the blood-brain-barrier (BBB), which limits the brain penetration of many anticancer drugs. BBB integrity is often compromised in tumors, referred to as the blood-brain-tumor-barrier (BBTB), and the impact of a compromised BBTB on the therapeutic sensitivity of brain tumors has been clearly shown for a few selected agents. However, the heterogeneity of barrier alteration observed within a single tumor and across distinct pediatric tumor types represents an additional challenge. Herein, we discuss what is known regarding the heterogeneity of tumor-associated vasculature in pediatric brain tumors. We discuss innovative and complementary preclinical model systems that will facilitate real-time functional analyses of BBTB for all pediatric brain tumor types. We believe a broader use of these preclinical models will enable us to develop a greater understanding of the processes underlying tumor-associated vasculature formation and ultimately more efficacious treatment options.

Trigeminal trophic syndrome in a pediatric patient with diffuse intrinsic pontine glioma

A 13-year-old girl with a history of diffuse intrinsic pontine glioma (DIPG) suffered from progressively worsening facial ulcerations secondary to paresthesia-induced self-excoriation. She was diagnosed with trigeminal trophic syndrome (TTS) induced by DIPG and struggled to heal her lesions in the background of this excoriation disorder. A multidisciplinary approach that included mood disorder management with sertraline and amitriptyline helped diminish paresthesia, improve her quality of life, and promote healing of the ulcers despite the progression of her DIPG. This case highlights the multifactorial complexity of TTS in pediatric patients and the need for successful management strategies.

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.

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

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

Defining tumor-associated vascular heterogeneity in pediatric high-grade and diffuse midline gliomas

The blood–brain barrier (BBB) plays important roles in brain tumor pathogenesis and treatment response, yet our understanding of its function and heterogeneity within or across brain tumor types remains poorly characterized. Here we analyze the neurovascular unit (NVU) of pediatric high-grade glioma (pHGG) and diffuse midline glioma (DMG) using patient derived xenografts and natively forming glioma mouse models. We show tumor-associated vascular differences between these glioma subtypes, and parallels between PDX and mouse model systems, with DMG models maintaining a more normal vascular architecture, BBB function and endothelial transcriptional program relative to pHGG models. Unlike prior work in angiogenic brain tumors, we find that expression of secreted Wnt antagonists do not alter the tumor-associated vascular phenotype in DMG tumor models. Together, these findings highlight vascular heterogeneity between pHGG and DMG and differences in their response to alterations in developmental BBB signals that may participate in driving these pathological differences.

Radiosensitization in Pediatric High-Grade Glioma: Targets, Resistance and Developments

Pediatric high-grade gliomas (pHGG) are the leading cause of cancer-related death in children. These epigenetically dysregulated tumors often harbor mutations in genes encoding histone 3, which contributes to a stem cell-like, therapy-resistant phenotype. Furthermore, pHGG are characterized by a diffuse growth pattern, which, together with their delicate location, makes complete surgical resection often impossible. Radiation therapy (RT) is part of the standard therapy against pHGG and generally the only modality, apart from surgery, to provide symptom relief and a delay in tumor progression. However, as a single treatment modality, RT still offers no chance for a cure. As with most therapeutic approaches, irradiated cancer cells often acquire resistance mechanisms that permit survival or stimulate regrowth after treatment, thereby limiting the efficacy of RT. Various preclinical studies have investigated radiosensitizers in pHGG models, without leading to an improved clinical outcome for these patients. However, our recently improved molecular understanding of pHGG generates new opportunities to (re-)evaluate radiosensitizers in these malignancies. Furthermore, the use of radio-enhancing agents has several benefits in pHGG compared to other cancers, which will be discussed here. This review provides an overview and a critical evaluation of the radiosensitization strategies that have been studied to date in pHGG, thereby providing a framework for improving radiosensitivity of these rapidly fatal brain tumors.

Targeting tumor hypoxia and mitochondrial metabolism with anti-parasitic drugs to improve radiation response in high-grade gliomas

High-grade gliomas (HGGs), including glioblastoma and diffuse intrinsic pontine glioma, are amongst the most fatal brain tumors. These tumors are associated with a dismal prognosis with a median survival of less than 15 months. Radiotherapy has been the mainstay of treatment of HGGs for decades; however, pronounced radioresistance is the major obstacle towards the successful radiotherapy treatment. Herein, tumor hypoxia is identified as a significant contributor to the radioresistance of HGGs as oxygenation is critical for the effectiveness of radiotherapy. Hypoxia plays a fundamental role in the aggressive and resistant phenotype of all solid tumors, including HGGs, by upregulating hypoxia-inducible factors (HIFs) which stimulate vital enzymes responsible for cancer survival under hypoxic stress. Since current attempts to target tumor hypoxia focus on reducing oxygen demand of tumor cells by decreasing oxygen consumption rate (OCR), an attractive strategy to achieve this is by inhibiting mitochondrial oxidative phosphorylation, as it could decrease OCR, and increase oxygenation, and could therefore improve the radiation response in HGGs. This approach would also help in eradicating the radioresistant glioma stem cells (GSCs) as these predominantly rely on mitochondrial metabolism for survival. Here, we highlight the potential for repurposing anti-parasitic drugs to abolish tumor hypoxia and induce apoptosis of GSCs. Current literature provides compelling evidence that these drugs (atovaquone, ivermectin, proguanil, mefloquine, and quinacrine) could be effective against cancers by mechanisms including inhibition of mitochondrial metabolism and tumor hypoxia and inducing DNA damage. Therefore, combining these drugs with radiotherapy could potentially enhance the radiosensitivity of HGGs. The reported efficacy of these agents against glioblastomas and their ability to penetrate the blood-brain barrier provides further support towards promising results and clinical translation of these agents for HGGs treatment.

Development of a clinical scale for assessment of patients with diffuse intrinsic pontine glioma (DIPG) receiving experimental therapy: the PONScore

PURPOSE

Monitoring neurological side-effects in experimental therapy for diffuse intrinsic pontine glioma (DIPG) can be challenging. We aimed to develop a neurological scale that could be used by non-specialists to quantify neurological changes during experimental treatment of DIPG.

METHODS

We developed the Pontine Observational Neurological Score (PONScore) to measure signs and symptoms of DIPG by adapting validated assessment scales of neurological signs and symptoms in children. We developed a prototype score, taught it to paediatric intensive care nursing staff, who used the Score to assess children receiving awake pontine infusion of chemotherapy for treatment of DIPG. We used their feedback to develop the PONScore. Points are allocated for headache, ophthalmoplegia, facial and tongue weakness, dysarthria, paraesthesia, limb weakness and dysmetria with increasing scores reflecting increasing disability. The PONScore was administered every hour during awake pontine infusion. Correlation and agreement calculations between nursing staff, as non-specialists, and a specialist rater were performed in 30 infusions in 6 children (aged 8-11). Changes in PONScore versus volume of infusion are described in a further 55 infusions in 8 children (aged 3-11).

RESULTS

The PONScore demonstrated excellent intra-rater reliability with an intra-class co-efficient of 0.98 (95% CI 0.97-0.99; p-value < 0.001) between a specialist and non-specialist raters with strong correlation between scores and a Spearman correlation coefficient of 0.985 (p < 0.001). PONScores increased from 3.3 to 5.7 (p-value < 0.001) during infusion reflecting accumulation of neurological signs and symptoms during infusion.

CONCLUSIONS

We describe a novel neurological scale that can be used by non-specialists to describe acute neurological changes in children receiving experimental therapy for DIPG. Prospective validation as part of a clinical trial is required.

Inhibition of mutant PPM1D enhances DNA damage response and growth suppressive effects of ionizing radiation in diffuse intrinsic pontine glioma

BACKGROUND

Children with diffuse intrinsic pontine glioma (DIPG) succumb to disease within 2 years of diagnosis despite treatment with ionizing radiation (IR) and/or chemotherapy. Our aim was to determine the role of protein phosphatase, magnesium-dependent 1, delta (PPM1D) mutation, present in up to 25% of cases, in DIPG pathogenesis and treatment.

METHODS

Using genetic and pharmacologic approaches, we assayed effects of PPM1D mutation on DIPG growth and murine survival. We assayed effects of targeting mutated PPM1D alone or with IR on signaling, cell cycle, proliferation, and apoptosis in patient-derived DIPG cells in vitro, in organotypic brain slices, and in vivo.

RESULTS

PPM1D-mutated DIPG cell lines exhibited increased proliferation in vitro and in vivo, conferring reduced survival in orthotopically xenografted mice, through stabilization of truncated PPM1D protein and inactivation of DNA damage response (DDR) effectors p53 and H2A.X. PPM1D knockdown or treatment with PPM1D inhibitors suppressed growth of PPM1D-mutated DIPGs in vitro. Orthotopic xenografting of PPM1D short hairpin RNA-transduced or PPM1D inhibitor-treated, PPM1D-mutated DIPG cells into immunodeficient mice resulted in reduced tumor proliferation, increased apoptosis, and extended mouse survival. PPM1D inhibition had similar effects to IR alone on DIPG growth inhibition and augmented the anti-proliferative and pro-apoptotic effects of IR in PPM1D-mutated DIPG models.

CONCLUSIONS

PPM1D mutations inactivate DDR and promote DIPG growth. Treatment with PPM1D inhibitors activated DDR pathways and enhanced the anti-proliferative and pro-apoptotic effects of IR in DIPG models. Our results support continued development of PPM1D inhibitors for phase I/II trials in children with DIPG.

Development of a human in vitro blood-brain tumor barrier model of diffuse intrinsic pontine glioma to better understand the chemoresistance

Background

Pediatric diffuse intrinsic pontine glioma (DIPG) represents one of the most devastating and lethal brain tumors in children with a median survival of 12 months. The high mortality rate can be explained by the ineligibility of patients to surgical resection due to the diffuse growth pattern and midline localization of the tumor. While the therapeutic strategies are unfortunately palliative, the blood–brain barrier (BBB) is suspected to be responsible for the treatment inefficiency. Located at the brain capillary endothelial cells (ECs), the BBB has specific properties to tightly control and restrict the access of molecules to the brain parenchyma including chemotherapeutic compounds. However, these BBB specific properties can be modified in a pathological environment, thus modulating brain exposure to therapeutic drugs. Hence, this study aimed at developing a syngeneic human blood–brain tumor barrier model to understand how the presence of DIPG impacts the structure and function of brain capillary ECs.

Methods

A human syngeneic in vitro BBB model consisting of a triple culture of human (ECs) (differentiated from CD34⁺-stem cells), pericytes and astrocytes was developed. Once validated in terms of BBB phenotype, this model was adapted to develop a blood–brain tumor barrier (BBTB) model specific to pediatric DIPG by replacing the astrocytes by DIPG-007, -013 and -014 cells. The physical and metabolic properties of the BBTB ECs were analyzed and compared to the BBB ECs. The permeability of both models to chemotherapeutic compounds was evaluated.

Results

In line with clinical observation, the integrity of the BBTB ECs remained intact until 7 days of incubation. Both transcriptional expression and activity of efflux transporters were not strongly modified by the presence of DIPG. The permeability of ECs to the chemotherapeutic drugs temozolomide and panobinostat was not affected by the DIPG environment.

Conclusions

This original human BBTB model allows a better understanding of the influence of DIPG on the BBTB ECs phenotype. Our data reveal that the chemoresistance described for DIPG does not come from the development of a “super BBB”. These results, validated by the absence of modification of drug transport through the BBTB ECs, point out the importance of understanding the implication of the different protagonists in the pathology to have a chance to significantly improve treatment efficiency.

Pediatric intrinsic brainstem lesions: clinical, imaging, histological characterization, and predictors of survival

PURPOSE

Brainstem lesions comprise 10-20% of all pediatric brain tumors. Over the past years, the benefits of stereotactic biopsy versus the use alone of MRI features to guide treatment have been controversial.

METHODS

Retrospective study with pediatric patients submitted to stereotactic brainstem biopsies between 2008 and 2018. Demographic, clinical, imaging, and surgical characteristics were recorded, as well as the histological diagnosis, complications, and survival. Predictors of survival were evaluated through Cox regression models after multivariate adjustment.

RESULTS

Twenty-six patients (mean age of 8.8 ± 4.3 years and 14 female). Diagnosis was reached on 84.6% (95% CI 65.1-95.6%) of the patients. Glioma was diagnosed on 20 cases (11 high-grade and 9 low-grade lesions). There was no association between age and gender and the dichotomized histological diagnosis. Contrast enhancement, diffuse distribution, invasion of adjacent structures, and remote injury were present on 62.5%, 75.0%, 62.5%, and 25.0% of the cases. Hydrocephalus at admission was present on almost half of the patients (46.2%). Only radiological invasion of adjacent structures had a possible association with high-grade lesions (p = 0.057). Surgical trajectory was trans-cerebellar in most of the cases (79.9%). There were no major complications and only two minor/transitory complications. Poorer survival was independently associated with high-grade lesions (HR 32.14, 95% CI 1.40-735.98, p = 0.030) and contrast enhancement at MRI (HR 36.54, 95% CI 1.40-952.26, p = 0.031).

CONCLUSIONS

Stereotactic biopsy was safe and allows successful tissue sampling for a definite diagnosis. Poorer survival was independently associated with high-grade and contrast-enhancing lesions.

Oncohistone Mutations in Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is a lethal pediatric tumor with no currently available treatment options. More than 60-70% DIPG tumors harbor heterozygous mutations at genes encoding histone H3 proteins that replace lysine 27 with methionine (K27M). In this review, we discuss how K27M mutation reprograms the cancer epigenome to lead to tumorigenesis, and highlight potential drug targets and therapeutic agents for DIPG.

CDK4/6 and PDGFRA Signaling as Therapeutic Targets in Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine gliomas (DIPGs) are incurable childhood brain tumors, whereby the standard of care is focal radiation, a treatment that provides temporary relief for most patients. Surprisingly, decades of clinical trials have failed to identify additional therapies that can prolong survival in this disease. In this conference manuscript, we discuss how genetic engineered mouse modeling techniques with the use of a retroviral gene delivery system can help dissect the complex pathophysiology of this disease. With this approach, autochthonous murine DIPG models can be readily induced to (1) help interrogate the function of novel genetic alterations in tumorigenesis, (2) identify candidate cells of origin for this disease, (3) address how region-specific differences in the central nervous system influence the process of gliomagenesis, and (4) evaluate novel therapeutics in an immunocompetent model.

Vaccination in the immunotherapy of glioblastoma

Glioblastoma remains one of the most common central nervous system tumors with an extremely poor prognosis. Recently, rapid progress in immunotherapy has provided new options for the treatment of glioblastoma. Vaccination, the primary method of immunotherapy, stimulates the body's tumor-specific immune response by the injection of foreign antigens. Peptide vaccines involve the injection of tumor-specific antigens, such as EGFRvIII or heat-shock proteins. Cell-based vaccines, which primarily include dendritic cell vaccines and tumor cell vaccines, involve injections of ex vivo-modified cells. Despite the encouraging results of phase I/II clinical trials, no successful phase III clinical trials involving glioblastoma immunotherapy, including glioblastoma vaccinations, have been reported to date. In this review, the authors summarize the published outcomes of glioblastoma vaccine therapy, explore its future prospects based on ongoing clinical trials, and discuss combined therapy as a future direction for glioblastoma treatment.

H3.1 K36M mutation in a congenital-onset soft tissue neoplasm

We describe a patient who presented with a congenital soft tissue lesion initially diagnosed as infantile fibromatosis at 15 days of age. Unusually, the mass demonstrated malignant progression leading to death at 20 months of age. Biological progression to malignancy is not known to occur in fibromatosis, and fibrosarcoma is not known to progress from a benign lesion. Whole-exome sequencing of the tumor identified a driver mutation in histone H3.1 at lysine (K)36. Our findings support the link between oncohistones and infantile soft tissue tumors and provide additional evidence for the oncogenic effects of p.K36M in H3 variants.

Immunotherapy for Pediatric Brain Tumors

Malignant brain tumors are the most common cause of solid cancer death in children. New targeted therapies are vital to improve treatment outcomes, but must be developed to enable trafficking across the blood brain barrier (BBB). Since activated T cells cross the BBB, cancer immunotherapy can be harnessed to unlock the cytotoxic potential of the immune system. However, standard of care treatments (i.e., chemotherapy and radiation) applied concomitant to pediatric brain tumor immunotherapy may abrogate induction of immunotherapeutic responses. This review will discuss the development of immunotherapies within this paradigm using emerging approaches being investigated in phase I/II trials in children with refractory brain tumors, including checkpoint inhibitors, vaccine immunotherapy, and adoptive cell therapy.

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.

Correlation of 18F-FDG PET and MRI Apparent Diffusion Coefficient Histogram Metrics with Survival in Diffuse Intrinsic Pontine Glioma: A Report from the Pediatric Brain Tumor Consortium

The purpose of this study was to describe baseline ¹⁸F-FDG PET voxel characteristics in pediatric diffuse intrinsic pontine glioma (DIPG) and to correlate these metrics with baseline MRI apparent diffusion coefficient (ADC) histogram metrics, progression-free survival (PFS), and overall survival. Methods: Baseline brain ¹⁸F-FDG PET and MRI scans were obtained in 33 children from Pediatric Brain Tumor Consortium clinical DIPG trials. ¹⁸F-FDG PET images, postgadolinium MR images, and ADC MR images were registered to baseline fluid attenuation inversion recovery MR images. Three-dimensional regions of interest on fluid attenuation inversion recovery MR images and postgadolinium MR images and ¹⁸F-FDG PET and MR ADC histograms were generated. Metrics evaluated included peak number, skewness, and kurtosis. Correlation between PET and MR ADC histogram metrics was evaluated. PET pixel values within the region of interest for each tumor were plotted against MR ADC values. The association of these imaging markers with survival was described. Results: PET histograms were almost always unimodal (94%, vs. 6% bimodal). None of the PET histogram parameters (skewness or kurtosis) had a significant association with PFS, although a higher PET postgadolinium skewness tended toward a less favorable PFS (hazard ratio, 3.48; 95% confidence interval [CI], 0.75-16.28 [P = 0.11]). There was a significant association between higher MR ADC postgadolinium skewness and shorter PFS (hazard ratio, 2.56; 95% CI, 1.11-5.91 [P = 0.028]), and there was the suggestion that this also led to shorter overall survival (hazard ratio, 2.18; 95% CI, 0.95-5.04 [P = 0.067]). Higher MR ADC postgadolinium kurtosis tended toward shorter PFS (hazard ratio, 1.30; 95% CI, 0.98-1.74 [P = 0.073]). PET and MR ADC pixel values were negatively correlated using the Pearson correlation coefficient. Further, the level of PET and MR ADC correlation was significantly positively associated with PFS; tumors with higher values of ADC-PET correlation had more favorable PFS (hazard ratio, 0.17; 95% CI, 0.03-0.89 [P = 0.036]), suggesting that a higher level of negative ADC-PET correlation leads to less favorable PFS. A more significant negative correlation may indicate higher-grade elements within the tumor leading to poorer outcomes. Conclusion:¹⁸F-FDG PET and MR ADC histogram metrics in pediatric DIPG demonstrate different characteristics with often a negative correlation between PET and MR ADC pixel values. A higher negative correlation is associated with a worse PFS, which may indicate higher-grade elements within the tumor.

Development of a DIPG Orthotopic Model in Mice Using an Implantable Guide-Screw System

Objective

In this work we set to develop and to validate a new in vivo frameless orthotopic Diffuse Intrinsic Pontine Glioma (DIPG) model based in the implantation of a guide-screw system.

Methods

It consisted of a guide-screw also called bolt, a Hamilton syringe with a 26-gauge needle and an insulin-like 15-gauge needle. The guide screw is 2.6 mm in length and harbors a 0.5 mm central hole which accepts the needle of the Hamilton syringe avoiding a theoretical displacement during insertion. The guide-screw is fixed on the mouse skull according to the coordinates: 1mm right to and 0.8 mm posterior to lambda. To reach the pons the Hamilton syringe is adjusted to a 6.5 mm depth using a cuff that serves as a stopper. This system allows delivering not only cells but also any kind of intratumoral chemotherapy, antibodies or gene/viral therapies.

Results

The guide-screw was successfully implanted in 10 immunodeficient mice and the animals were inoculated with DIPG human cell lines during the same anesthetic period. All the mice developed severe neurologic symptoms and had a median overall survival of 95 days ranging the time of death from 81 to 116 days. Histopathological analysis confirmed tumor into the pons in all animals confirming the validity of this model.

Conclusion

Here we presented a reproducible and frameless DIPG model that allows for rapid evaluation of tumorigenicity and efficacy of chemotherapeutic or gene therapy products delivered intratumorally to the pons.