Prolonged survival after treatment of diffuse intrinsic pontine glioma with radiation, temozolamide, and bevacizumab: report of 2 cases

Chemotherapy in pediatric brain tumor and the challenge of the blood-brain barrier

BACKGROUND

Pediatric brain tumors (PBT) stand as the leading cause of cancer-related deaths in children. Chemoradiation protocols have improved survival rates, even for non-resectable tumors. Nonetheless, radiation therapy carries the risk of numerous adverse effects that can have long-lasting, detrimental effects on the quality of life for survivors. The pursuit of chemotherapeutics that could obviate the need for radiotherapy remains ongoing. Several anti-tumor agents, including sunitinib, valproic acid, carboplatin, and panobinostat, have shown effectiveness in various malignancies but have not proven effective in treating PBT. The presence of the blood-brain barrier (BBB) plays a pivotal role in maintaining suboptimal concentrations of anti-cancer drugs in the central nervous system (CNS). Ongoing research aims to modulate the integrity of the BBB to attain clinically effective drug concentrations in the CNS. However, current findings on the interaction of exogenous chemical agents with the BBB remain limited and do not provide a comprehensive explanation for the ineffectiveness of established anti-cancer drugs in PBT.

METHODS

We conducted our search for chemotherapeutic agents associated with the blood-brain barrier (BBB) using the following keywords: Chemotherapy in Cancer, Chemotherapy in Brain Cancer, Chemotherapy in PBT, BBB Inhibition of Drugs into CNS, Suboptimal Concentration of CNS Drugs, PBT Drugs and BBB, and Potential PBT Drugs. We reviewed each relevant article before compiling the information in our manuscript. For the generation of figures, we utilized BioRender software.

FOCUS

We focused our article search on chemical agents for PBT and subsequently investigated the role of the BBB in this context. Our search criteria included clinical trials, both randomized and non-randomized studies, preclinical research, review articles, and research papers.

FINDING

Our research suggests that, despite the availability of potent chemotherapeutic agents for several types of cancer, the effectiveness of these chemical agents in treating PBT has not been comprehensively explored. Additionally, there is a scarcity of studies examining the role of the BBB in the suboptimal outcomes of PBT treatment, despite the effectiveness of these drugs for other types of tumors.

ImmunoPET Directed to the Brain: A New Tool for Preclinical and Clinical Neuroscience

Immuno-positron emission tomography (immunoPET) is a non-invasive in vivo imaging method based on tracking and quantifying radiolabeled monoclonal antibodies (mAbs) and other related molecules, such as antibody fragments, nanobodies, or affibodies. However, the success of immunoPET in neuroimaging is limited because intact antibodies cannot penetrate the blood-brain barrier (BBB). In neuro-oncology, immunoPET has been successfully applied to brain tumors because of the compromised BBB. Different strategies, such as changes in antibody properties, use of physiological mechanisms in the BBB, or induced changes to BBB permeability, have been developed to deliver antibodies to the brain. These approaches have recently started to be applied in preclinical central nervous system PET studies. Therefore, immunoPET could be a new approach for developing more specific PET probes directed to different brain targets.

Does a Bevacizumab-based regime have a role in the treatment of children with diffuse intrinsic pontine glioma? A systematic review

Background

There are no effective treatments for diffuse intrinsic pontine glioma (DIPG); median survival is 11.2 months. Bevacizumab has the potential to improve quality of life (QOL) and survival in DIPG but has never been evaluated systematically. The aim of this review was to assess Bevacizumab’s role in the treatment of DIPG.

Methods

MEDLINE, EMBASE, Scopus, and Web of Science were searched for relevant studies using terms developed from alternatives for Bevacizumab and DIPG. One reviewer screened titles and abstracts, then two reviewers screened full texts. Data were extracted into tables and quality assessed using methodological index for non-randomized studies and JBI tools.

Results

Searching revealed 1001 papers; after deduplication 851 remained. After screening of titles and abstracts, then 28 full texts, 11 studies were included. Four studies reported a median overall survival longer than historical data, however, two found no significant impact of Bevacizumab. Five studies reported a radiological response in a proportion of participants and two reported no response. Three studies, evaluating clinical response, reported improvement in a proportion of patients. Three studies, evaluating QOL, reported stability or improvement. Four studies, evaluating steroid use, reported reductions in the proportion of patients receiving steroids. In radiation necrosis treatment, Bevacizumab led to clinical improvement in 6/12 patients in 2 studies and permitted a reduction in steroid use in most patients.

Conclusions

Insufficient evidence means the role of Bevacizumab in the treatment of DIPG is unclear. However, Bevacizumab may be beneficial to some patients. The review highlights the need for further research in this area.

[The art of war as applied to pediatric gliomas: Know your enemy]

Pediatric brain cancers represent the most frequent solid tumors and the leading cause of cancer-driven mortality in children. Pediatric High Grade Gliomas display a very poor prognosis. Among these, DIPG (Diffuse Intrinsic Pontine Gliomas), localized to the brain stem, cannot benefit from a total exeresis due to this critical location and to their highly infiltrating nature. Radiotherapy remains the standard treatment against these tumors for almost five decades, and attempts to improve the prognosis of patients with chemotherapy or targeted therapies have failed. Thanks to the rise of high throughput sequencing, the knowledge of molecular alterations in pediatric gliomas strongly progressed and allowed to highlight distinct biomolecular entities and to establish more accurate diagnoses. In this review, we summarize this new information and the perspectives that it brings for clinical strategies.

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.

Use of Antiangiogenic Therapies in Pediatric Solid Tumors

Cancer is an important cause of death in childhood. In recent years, scientists have made an important effort to achieve greater precision and more personalized treatments against cancer. But since only a few pediatric patients have identifiable therapeutic targets, other ways to stop the neoplastic cell proliferation and dissemination are needed. Therefore, the inhibition of general processes involved in the growth and behavior of tumors can be a relevant strategy for the development of new cancer therapies. In the case of solid tumors, one of these processes is angiogenesis, essential for tumor growth and generation of metastases. This review summarizes the results obtained with the use of antiangiogenic drugs in the main pediatric malignant solid tumors and also an overview of clinical trials currently underway. It should be noted that due to the rarity and heterogeneity of the different types of pediatric cancer, most studies on antiangiogenic drugs include only a small number of patients or isolated clinical cases, so they are not conclusive and further studies are needed.

A retrospective study of bevacizumab for treatment of brainstem glioma with malignant features

Brainstem glioma is impossible to resect completely, and patients with this type of glioma show a poor prognosis. Therefore, a more effective adjuvant therapy is required to prolong survival. Bevacizumab is an endothelial growth factor monoclonal antibody with strong anti-vascular effects, which may suppress tumor progression. We performed a retrospective study of data from 6 patients with brainstem glioma showing malignant features who were treated with bevacizumab. Tumor-associated lesions, as evaluated by T2 weighted or fluid-attenuated inversion-recovery magnetic resonance imaging, were reduced in all patients, although the timing of the start of bevacizumab administration and pretreatment were not uniform. Clinical symptoms improved in 4 patients and progression was inhibited in 2 patients. The Karnofsky performance status improved from 56.7 to 71.7 on average. The median reduction ratio of tumor-associated lesions was 76.3%, but tumor suppression did not last in any of the cases. Furthermore, 5 patients died of tumor progression, and 1 patient died of a complication of necrotizing colitis. The median progression-free survival after bevacizumab administration was 7 months. The median overall survival after diagnosis was 16.5 months. Bevacizumab might be a potential therapeutic option for progressive brainstem gliomas with malignant features.

Molecular Drug Imaging: 89Zr-Bevacizumab PET in Children with Diffuse Intrinsic Pontine Glioma

Predictive tools for guiding therapy in children with brain tumors are urgently needed. In this first molecular drug imaging study in children, we investigated whether bevacizumab can reach tumors in children with diffuse intrinsic pontine glioma (DIPG) by measuring the tumor uptake of ⁸⁹Zr-labeled bevacizumab by PET. In addition, we evaluated the safety of the procedure in children and determined the optimal time for imaging. Methods: Patients received ⁸⁹Zr-bevacizumab (0.1 mg/kg; 0.9 MBq/kg) at least 2 wk after completing radiotherapy. Whole-body PET/CT scans were obtained 1, 72, and 144 h after injection. All patients underwent contrast (gadolinium)-enhanced MRI. The biodistribution of ⁸⁹Zr-bevacizumab was quantified as SUVs. Results: Seven DIPG patients (4 boys; 6-17 y old) were scanned without anesthesia. No adverse events occurred. Five of 7 primary tumors showed focal ⁸⁹Zr-bevacizumab uptake (SUVs at 144 h after injection were 1.0-6.7), whereas no significant uptake was seen in the healthy brain. In 1 patient, multiple metastases all showed positive PET results. We observed inter- and intratumoral heterogeneity of uptake, and ⁸⁹Zr-bevacizumab uptake was present predominantly (in 4/5 patients) within MRI contrast-enhanced areas, although ⁸⁹Zr-bevacizumab uptake in these areas was variable. Tumor targeting results were quantitatively similar at 72 and 144 h after injection, but tumor-to-blood-pool SUV ratios increased with time after injection (P = 0.045). The mean effective dose per patient was 0.9 mSv/MBq (SD, 0.3 mSv/MBq). Conclusion:⁸⁹Zr-bevacizumab PET studies are feasible in children with DIPG. The data suggest considerable heterogeneity in drug delivery among patients and within DIPG tumors and a positive, but not 1:1, correlation between MRI contrast enhancement and ⁸⁹Zr-bevacizumab uptake. The optimal time for scanning is 144 h after injection. Tumor ⁸⁹Zr-bevacizumab accumulation assessed by PET scanning may help in the selection of patients with the greatest chance of benefit from bevacizumab treatment.

Bevacizumab Targeting Diffuse Intrinsic Pontine Glioma: Results of 89Zr-Bevacizumab PET Imaging in Brain Tumor Models

The role of the VEGF inhibitor bevacizumab in the treatment of diffuse intrinsic pontine glioma (DIPG) is unclear. We aim to study the biodistribution and uptake of zirconium-89 ((89)Zr)-labeled bevacizumab in DIPG mouse models. Human E98-FM, U251-FM glioma cells, and HSJD-DIPG-007-FLUC primary DIPG cells were injected into the subcutis, pons, or striatum of nude mice. Tumor growth was monitored by bioluminescence imaging (BLI) and visualized by MRI. Seventy-two to 96 hours after (89)Zr-bevacizumab injections, mice were imaged by positron emission tomography (PET), and biodistribution was analyzed ex vivo High VEGF expression in human DIPG was confirmed in a publically available mRNA database, but no significant (89)Zr-bevacizumab uptake could be detected in xenografts located in the pons and striatum at an early or late stage of the disease. E98-FM, and to a lesser extent the U251-FM and HSJD-DIPG-007 subcutaneous tumors, showed high accumulation of (89)Zr-bevacizumab. VEGF expression could not be demonstrated in the intracranial tumors by in situ hybridization (ISH) but was clearly present in the perinecrotic regions of subcutaneous E98-FM tumors. The poor uptake of (89)Zr-bevacizumab in xenografts located in the brain suggests that VEGF targeting with bevacizumab has limited efficacy for diffuse infiltrative parts of glial brain tumors in mice. Translating these results to the clinic would imply that treatment with bevacizumab in patients with DIPG is only justified after targeting of VEGF has been demonstrated by (89)Zr-bevacizumab immuno-PET. We aim to confirm this observation in a clinical PET study with patients with DIPG. Mol Cancer Ther; 15(9); 2166-74. ©2016 AACR.

The challenges and the promise of molecular targeted therapy in malignant gliomas

Malignant gliomas are the most common malignant primary brain tumors and one of the most challenging forms of cancers to treat. Despite advances in conventional treatment, the outcome for patients remains almost universally fatal. This poor prognosis is due to therapeutic resistance and tumor recurrence after surgical removal. However, over the past decade, molecular targeted therapy has held the promise of transforming the care of malignant glioma patients. Significant progress in understanding the molecular pathology of gliomagenesis and maintenance of the malignant phenotypes will open opportunities to rationally develop new molecular targeted therapy options. Recently, therapeutic strategies have focused on targeting pro-growth signaling mediated by receptor tyrosine kinase/RAS/phosphatidylinositol 3-kinase pathway, proangiogenic pathways, and several other vital intracellular signaling networks, such as proteasome and histone deacetylase. However, several factors such as cross-talk between the altered pathways, intratumoral molecular heterogeneity, and therapeutic resistance of glioma stem cells (GSCs) have limited the activity of single agents. Efforts are ongoing to study in depth the complex molecular biology of glioma, develop novel regimens targeting GSCs, and identify biomarkers to stratify patients with the individualized molecular targeted therapy. Here, we review the molecular alterations relevant to the pathology of malignant glioma, review current advances in clinical targeted trials, and discuss the challenges, controversies, and future directions of molecular targeted therapy.

A pilot study of bevacizumab-based therapy in patients with newly diagnosed high-grade gliomas and diffuse intrinsic pontine gliomas

Although bevacizumab has not proven effective in adults with newly diagnosed high-grade gliomas (HGG), feasibility in newly diagnosed children with diffuse intrinsic pontine gliomas (DIPG) or HGG has not been reported in a prospective study. In a safety and feasibility study, children and young adults with newly diagnosed HGG received radiotherapy (RT) with bevacizumab (10 mg/kg: days 22, 36) and temozolomide (75-90 mg/m(2)/day for 42 days) followed by bevacizumab (10 mg/kg, days 1, 15), irinotecan (125 mg/m(2), days 1, 15) and temozolomide (150 mg/m(2)/day days 1-5). DIPG patients did not receive temozolomide. Telomerase activity, quality of life (QOL), and functional outcomes were assessed. Among 27 eligible patients (15 DIPG, 12 HGG), median age 10 years (range 3-29 years), 6 discontinued therapy for toxicity: 2 during RT (grade 4 thrombocytopenia, grade 3 hepatotoxicity) and 4 during maintenance therapy (grade 3: thrombosis, hypertension, skin ulceration, and wound dehiscence). Commonest ≥grade 3 toxicities included lymphopenia, neutropenia and leukopenia. Grade 3 hypertension occurred in 2 patients. No intracranial hemorrhages occurred. For DIPG patients, median overall survival (OS) was 10.4 months. For HGG patients, 3-year progression free survival and OS were 33 % (SE ± 14 %) and 50 % (SE ± 14 %), respectively. All 3 tested tumor samples, demonstrated histone H3.3K27M (n = 2 DIPG) or G34R (n = 1 HGG) mutations. QOL scores improved over the course of therapy. A bevacizumab-based regimen is feasible and tolerable in newly diagnosed children and young adults with HGG and DIPG.

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

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

Radiation Necrosis in Pediatric Patients with Brain Tumors Treated with Proton Radiotherapy

BACKGROUND AND PURPOSE

Proton radiotherapy has been increasingly utilized to treat pediatric brain tumors, however, limited information exists regarding radiation necrosis among these patients. Our aim was to evaluate the incidence, timing, clinical significance, risk factors, and imaging patterns of radiation necrosis in pediatric patients with brain tumors treated with proton radiation therapy.

MATERIALS AND METHODS

A retrospective study was performed on 60 consecutive pediatric patients with primary brain tumors treated with proton radiation therapy. Radiation necrosis was assessed by examining serial MRIs and clinical records to determine the incidence, timing, risk factors, imaging patterns, and clinical significance associated with the development of radiation necrosis in these patients. Radiation necrosis was defined as areas of new enhancement within an anatomic region with previous exposure to proton beam therapy with subsequent decrease on follow-up imaging without changes in chemotherapy.

RESULTS

Thirty-one percent of patients developed radiation necrosis with a median time to development of 5.0 months (range, 3-11 months). Risk factors included multiple chemotherapy agents (>3 cytotoxic agents) and atypical teratoid rhabdoid tumor pathology (P = .03 and P = .03, respectively). The most common imaging patterns were small (median, 0.9 cm) and multifocal (63% of patients) areas of parenchymal enhancement remote from the surgical site. The median time to complete resolution on imaging was 5.3 months (range, 3-12 months). Among patients with imaging findings of radiation necrosis, 25% demonstrated severe symptoms with medical intervention indicated.

CONCLUSIONS

Pediatric patients with brain tumors treated with proton radiation therapy demonstrate a high incidence of radiation necrosis and a short time to development of necrosis. Multiple small areas of necrosis are frequently identified on imaging. Exposure to multiple chemotherapy agents was a significant risk factor associated with radiation necrosis in these patients.

Diffuse intrinsic pontine gliomas: treatments and controversies

Diffuse intrinsic pontine gliomas (DIPGs) are a fairly common pediatric brain tumor, and children with these tumors have a dismal prognosis. They generally are diagnosed within the first decade of life, and due to their location within the pons, these tumors are not surgically resectable. The median survival for children with DIPGs is less than 1 year, in spite of decades of clinical trial development of unique approaches to radiation therapy and chemotherapy. Novel therapies are under investigation for these deadly tumors. As clinicians and researchers make a concerted effort to obtain tumor tissue, the molecular signals of these tumors are being investigated in an attempt to uncover targetable therapies for DIPGs. In addition, direct application of chemotherapies into the tumor (convection-enhanced delivery) is being investigated as a novel delivery system for treatment of DIPGs. Overall, DIPGs require creative thinking and a disciplined approach for development of a therapy that can improve the prognosis for these unfortunate children.

Radiotherapy and the tumor microenvironment: mutual influence and clinical implications

Ionizing radiation has been employed in targeted cancer treatments for more than a century because of its cytotoxic effects on cancer cells. However, the responsiveness to radiation and the behavior of tumors in vivo may differ dramatically from observed behaviors of isolated cancer cells in vitro. While not fully understood, these discrepancies are due to a complex constellation of extracellular and intercellular factors that are together termed the tumor microenvironment. Radiation may alter or affect the components of the adjacent tumor microenvironment in significant ways, often with consequences for cancer cells beyond the direct effects of the radiation itself. Moreover, different microenvironmental states, whether induced or at baseline, can modulate or even attenuate the effects of radiation, with consequences for therapeutic efficacy. This chapter describes this bidirectional relationship in detail, exploring the role and clinical implications of the tumor microenvironment with respect to therapeutic irradiation.