Medical therapies for meningiomas

Spatial genomic, biochemical and cellular mechanisms underlying meningioma heterogeneity and evolution

Intratumor heterogeneity underlies cancer evolution and treatment resistance, but targetable mechanisms driving intratumor heterogeneity are poorly understood. Meningiomas are the most common primary intracranial tumors and are resistant to all medical therapies, and high-grade meningiomas have significant intratumor heterogeneity. Here we use spatial approaches to identify genomic, biochemical and cellular mechanisms linking intratumor heterogeneity to the molecular, temporal and spatial evolution of high-grade meningiomas. We show that divergent intratumor gene and protein expression programs distinguish high-grade meningiomas that are otherwise grouped together by current classification systems. Analyses of matched pairs of primary and recurrent meningiomas reveal spatial expansion of subclonal copy number variants associated with treatment resistance. Multiplexed sequential immunofluorescence and deconvolution of meningioma spatial transcriptomes using cell types from single-cell RNA sequencing show decreased immune infiltration, decreased MAPK signaling, increased PI3K-AKT signaling and increased cell proliferation, which are associated with meningioma recurrence. To translate these findings to preclinical models, we use CRISPR interference and lineage tracing approaches to identify combination therapies that target intratumor heterogeneity in meningioma cell co-cultures.

Establishment of tumor microenvironment-preserving organoid model from patients with intracranial meningioma

BACKGROUND

Although meningioma is the most common primary brain tumor, treatments rely on surgery and radiotherapy, and recurrent meningiomas have no standard therapeutic options due to a lack of clinically relevant research models. Current meningioma cell lines or organoids cannot reflect biological features of patient tumors since they undergo transformation along culture and consist of only tumor cells without microenvironment. We aim to establish patient-derived meningioma organoids (MNOs) preserving diverse cell types representative of the tumor microenvironment.

METHODS

The biological features of MNOs were evaluated using WST, LDH, and collagen-based 3D invasion assays. Cellular identities in MNOs were confirmed by immunohistochemistry (IHC). Genetic alteration profiles of MNOs and their corresponding parental tumors were obtained by whole-exome sequencing.

RESULTS

MNOs were established from four patients with meningioma (two grade 1 and two grade 2) at a 100% succession rate. Exclusion of enzymatic dissociation-reaggregation steps endowed MNOs with original histology and tumor microenvironment. In addition, we used a liquid media culture system instead of embedding samples into Matrigel, resulting in an easy-to-handle, cost-efficient, and time-saving system. MNOs maintained their functionality and morphology after long-term culture (> 9 wk) and repeated cryopreserving-recovery cycles. The similarities between MNOs and their corresponding parental tumors were confirmed by both IHC and whole-exome sequencing. As a representative application, we utilized MNOs in drug screening, and mifepristone, an antagonist of progesterone receptor, showed prominent antitumor efficacy with respect to viability, invasiveness, and protein expression.

CONCLUSION

Taken together, our MNO model overcame limitations of previous meningioma models and showed superior resemblance to parental tumors. Thus, our model could facilitate translational research identifying and selecting drugs for meningioma in the era of precision medicine.

Super-enhancer hijacking drives ectopic expression of hedgehog pathway ligands in meningiomas

Hedgehog signaling mediates embryologic development of the central nervous system and other tissues and is frequently hijacked by neoplasia to facilitate uncontrolled cellular proliferation. Meningiomas, the most common primary brain tumor, exhibit Hedgehog signaling activation in 6.5% of cases, triggered by recurrent mutations in pathway mediators such as SMO. In this study, we find 35.6% of meningiomas that lack previously known drivers acquired various types of somatic structural variations affecting chromosomes 2q35 and 7q36.3. These cases exhibit ectopic expression of Hedgehog ligands, IHH and SHH, respectively, resulting in Hedgehog signaling activation. Recurrent tandem duplications involving IHH permit de novo chromatin interactions between super-enhancers within DIRC3 and a locus containing IHH. Our work expands the landscape of meningioma molecular drivers and demonstrates enhancer hijacking of Hedgehog ligands as a route to activate this pathway  in neoplasia.

Intracranial meningiomas: an update of the 2021 World Health Organization classifications and review of management with a focus on radiation therapy

Meningiomas account for approximately one third of all primary intracranial tumors. Arising from the cells of the arachnoid mater, these neoplasms are found along meningeal surfaces within the calvarium and spinal canal. Many are discovered incidentally, and most are idiopathic, although risk factors associated with meningioma development include age, sex, prior radiation exposure, and familial genetic diseases. The World Health Organization grading system is based on histologic criteria, and are as follows: grade 1 meningiomas, a benign subtype; grade 2 meningiomas, which are of intermediately aggressive behavior and usually manifest histologic atypia; and grade 3, which demonstrate aggressive malignant behavior. Management is heavily dependent on tumor location, grade, and symptomatology. While many imaging-defined low grade appearing meningiomas are suitable for observation with serial imaging, others require aggressive management with surgery and adjuvant radiotherapy. For patients needing intervention, surgery is the optimal definitive approach with adjuvant radiation therapy guided by extent of resection, tumor grade, and location in addition to patient specific factors such as life expectancy. For grade 1 lesions, radiation can also be used as a monotherapy in the form of stereotactic radiosurgery or standard fractionated radiation therapy depending on tumor size, anatomic location, and proximity to dose-limiting organs at risk. Optimal management is paramount because of the generally long life-expectancy of patients with meningioma and the morbidity that can arise from tumor growth and recurrence as well as therapy itself.

Impact of H3K27 trimethylation loss in meningiomas: a meta-analysis

Trimethylation of lysine 27 on histone 3 (H3K27me3) loss has been implicated in worse prognoses for patients with meningiomas. However, there have been challenges in measuring H3K27me3 loss, quantifying its impact, and interpreting its clinical utility. We conducted a systematic review across Pubmed, Embase, and Web of Science to identify studies examining H3K27me3 loss in meningioma. Clinical, histopathological, and immunohistochemistry (IHC) characteristics were aggregated. A meta-analysis was performed using a random-effects model to assess prevalence of H3K27me3 loss and meningioma recurrence risk. Study bias was characterized using the NIH Quality Assessment Tool and funnel plots. Nine publications met inclusion criteria with a total of 2376 meningioma cases. The prevalence of H3K27me3 loss was 16% (95% CI 0.09-0.27), with higher grade tumors associated with a significantly greater proportion of loss. H3K27me3 loss was more common in patients who were male, had recurrent meningiomas, or required adjuvant radiation therapy. Patients were 1.70 times more likely to have tumor recurrence with H3K27me3 loss (95% CI 1.35-2.15). The prevalence of H3K27me3 loss in WHO grade 2 and 3 meningiomas was found to be significantly greater in tissue samples less than five years old versus tissue of all ages and when a broader definition of IHC staining loss was applied. This analysis demonstrates that H3K27me3 loss significantly associates with more aggressive meningiomas. While differences in IHC and tumor tissue age have led to heterogeneity in studying H3K27me3 loss, a robust prognostic signal is present. Our findings suggest an opportunity to improve study design and standardize tissue processing to optimize clinical viability of this epigenetic marker.

NOTCH3 drives meningioma tumorigenesis and resistance to radiotherapy

Meningiomas are the most common primary intracranial tumors1-3. Treatments for patients with meningiomas are limited to surgery and radiotherapy, and systemic therapies remain ineffective or experimental4,5. Resistance to radiotherapy is common in high-grade meningiomas6, and the cell types and signaling mechanisms driving meningioma tumorigenesis or resistance to radiotherapy are incompletely understood. Here we report NOTCH3 drives meningioma tumorigenesis and resistance to radiotherapy and find NOTCH3+ meningioma mural cells are conserved across meningiomas from humans, dogs, and mice. NOTCH3+ cells are restricted to the perivascular niche during meningeal development and homeostasis and in low-grade meningiomas but are expressed throughout high-grade meningiomas that are resistant to radiotherapy. Integrating single-cell transcriptomics with lineage tracing and imaging approaches across mouse genetic and xenograft models, we show NOTCH3 drives tumor initiating capacity, cell proliferation, angiogenesis, and resistance to radiotherapy to increase meningioma growth and reduce survival. An antibody stabilizing the extracellular negative regulatory region of NOTCH37,8 blocks meningioma tumorigenesis and sensitizes meningiomas to radiotherapy, reducing tumor growth and improving survival in preclinical models. In summary, our results identify a conserved cell type and signaling mechanism that underlie meningioma tumorigenesis and resistance to radiotherapy, revealing a new therapeutic vulnerability to treat meningiomas that are resistant to standard interventions.

Silica nanoparticles for brain cancer

INTRODUCTION

Brain cancer is a debilitating disease with a poor survival rate. There are significant challenges for effective treatment due to the presence of the blood-brain barrier (BBB) and blood-tumor barrier (BTB) which impedes drug delivery to tumor sites. Many nanomedicines have been tested in improving both the survival and quality of life of patients with brain cancer with the recent focus on inorganic nanoparticles such as silica nanoparticles (SNPs). This review examines the use of SNPs as a novel approach for diagnosing, treating, and theranostics of brain cancer.

AREAS COVERED

The review provides an overview of different brain cancers and current therapies available. A special focus on the key functional properties of SNPs is discussed which makes them an attractive material in the field of onco-nanomedicine. Strategies to overcome the BBB using SNPs are analyzed. Furthermore, recent advancements in active targeting, combination therapies, and innovative nanotherapeutics utilizing SNPs are discussed. Safety considerations, toxicity profiles, and regulatory aspects are addressed to provide an understanding of SNPs' translational potential.

EXPERT OPINION

SNPs have tremendous prospects in brain cancer research. The multifunctionality of SNPs has the potential to overcome both the BBB and BTB limitations and can be used for brain cancer imaging, drug delivery, and theranostics. The insights provided will facilitate the development of next-generation, innovative strategies, guiding future research toward improved diagnosis, targeted therapy, and better outcomes in brain cancer patients.

Management of Atypical and Anaplastic Meningiomas

Meningiomas are the most prevalent primary tumor of central nervous system origin, and although most of these neoplasms are benign, a small proportion exemplifies an aggressive profile characterized by high recurrence rates, pleomorphic histology, and overall resistance to standard treatment. Standard initial therapy for malignant meningiomas includes maximal safe surgical resection followed by focal radiation. The role for chemotherapy during recurrence of these aggressive meningiomas is less clear. Prognosis is poor, and recurrence of malignant meningiomas is high. This article provides an overview of atypical and anaplastic "malignant" meningiomas, their treatment, and ongoing research looking for more effective treatments.

Advances in the systemic therapy for recurrent meningiomas and the challenges ahead

INTRODUCTION

Meningiomas represent the most common primary neoplasms of the central nervous system (CNS). 20% present with atypical (WHO grade II) or malignant (grade III) meningiomas, which show aggressive biologic behavior and high recurrence. Although surgical resection and radiation therapy are the primary treatment options for these tumors, there is a subgroup of patients who do not respond well to or are poor candidates for these approaches, leading to the exploration of systemic therapies as an alternative.

AREAS COVERED

The literature on different therapeutic groups of systemic drugs for recurrent meningiomas is reviewed, with a focus on the different molecular targets. Past and current ongoing clinical trials are also discussed.

EXPERT OPINION

To date, there is no recognized treatment that has demonstrated a substantial increase in progression-free or overall survival rates. Nonetheless, therapies targeting anti-VEGF have exhibited more encouraging results in general. The examination of genomic and epigenomic traits of meningiomas, along with the integration of molecular markers into the latest WHO tumor grading system, has provided valuable insights. This has opened avenues for exploring numerous intracellular and extracellular pathways, as well as mutations, that have been targeted in ongoing clinical trials.

Wnt Signaling in Brain Tumors: A Challenging Therapeutic Target

The involvement of Wnt signaling in normal tissue homeostasis and disease has been widely demonstrated over the last 20 years. In particular, dysregulation of Wnt pathway components has been suggested as a relevant hallmark of several neoplastic malignancies, playing a role in cancer onset, progression, and response to treatments. In this review, we summarize the current knowledge on the instructions provided by Wnt signaling during organogenesis and, particularly, brain development. Moreover, we recapitulate the most relevant mechanisms through which aberrant Wnt pathway activation may impact on brain tumorigenesis and brain tumor aggressiveness, with a particular focus on the mutual interdependency existing between Wnt signaling components and the brain tumor microenvironment. Finally, the latest anti-cancer therapeutic approaches employing the specific targeting of Wnt signaling are extensively reviewed and discussed. In conclusion, here we provide evidence that Wnt signaling, due to its pleiotropic involvement in several brain tumor features, may represent a relevant target in this context, although additional efforts will be needed to: (i) demonstrate the real clinical impact of Wnt inhibition in these tumors; (ii) overcome some still unsolved concerns about the potential systemic effects of such approaches; (iii) achieve efficient brain penetration.

Docetaxel targets aggressive methylation profiles and serves as a radiosensitizer in high-risk meningiomas

BACKGROUND

Meningioma is the most common primary intracranial tumor in adults. A subset of these tumors recur and invade the brain, even after surgery and radiation, resulting in significant disability. There is currently no standard-of-care chemotherapy for meningiomas. As genomic DNA methylation profiling can prognostically stratify these lesions, we sought to determine whether any existing chemotherapies might be effective against meningiomas with high-risk methylation profiles.

METHODS

A previously published dataset of meningioma methylation profiles was used to screen for clinically significant CpG methylation events and associated cellular pathways. Based on these results, patient-derived meningioma cell lines were used to test candidate drugs in vitro and in vivo, including efficacy in conjunction with radiotherapy.

RESULTS

We identified 981 genes for which methylation of mapped CpG sites was related to progression-free survival in meningiomas. Associated molecular pathways were cross-referenced with FDA-approved cancer drugs, which nominated Docetaxel as a promising candidate for further preclinical analyses. Docetaxel arrested growth in 17 meningioma cell sources, representing all tumor grades, with a clinically favorable IC50 values ranging from 0.3 nM to 10.7 mM. The inhibitory effects of this medication scaled with tumor doubling time, with maximal benefit in fast-growing lesions. The combination of Docetaxel and radiation therapy increased markers of apoptosis and double-stranded DNA breaks, and extended the survival of mice engrafted with meningioma cells relative to either modality alone.

CONCLUSIONS

Global patterns of DNA methylation may be informative for the selection of chemotherapies against meningiomas, and existing drugs may enhance radiation sensitivity in high-risk cases.

Meningioma and Other Meningeal Tumors

Meningiomas develop from meningothelial cells and approximately account for more than 30 percent of central nervous system (CNS) tumors. They can occur anywhere in the dura, most often intracranially and at dural reflection sites. Half of the cases are usually at parasagittal/falcine and convexity locations; other common sites are sphenoid ridge, suprasellar, posterior fossa, and olfactory groove. The female-to-male ratio is approximately 2 or 3-1, and the median age at diagnosis is 65 years. Meningiomas are generally extremely slow-growing tumors; many are asymptomatic or paucisymptomatic at diagnosis and are discovered incidentally. Clinical manifestations, when present, are influenced by the tumor site and by the time course over which it develops. Meningiomas are divided into three grades. Grade I represents the vast majority of cases; they are considered typical or benign, although their CNS location can still lead to severe morbidity or mortality, resulting in a reported ten-year net survival of over 80%. Atypical (WHO grade II) meningiomas are considered "intermediate grade" malignancies and represent 5-7% of cases. They show a tendency for recurrence and malignant degeneration with a relevant increase in tumor cell migration and surrounding tissue infiltration; ten-year net survival is reported over 60%. The anaplastic subtype (WHO III) represents only 1-3% of cases, and it is characterized by a poor prognosis (ten-year net survival of 15%). The treatment of choice for these tumors stands on complete microsurgical resection in case the subsequent morbidities are assumed minimal. On the other hand, and in case the tumor is located in critical regions such as the skull base, or the patient may have accompanied comorbidities, or it is aimed to avoid intensive treatment, some other approaches, including stereotactic radiosurgery and radiotherapy, were recommended as safe and effective choices to be considered as a primary treatment option or complementary to surgery. Adjuvant radiosurgery/radiotherapy should be considered in the case of atypical and anaplastic histology, especially when a residual tumor is identifiable in postoperative imaging. A "watchful waiting" strategy appears reasonable for extremely old individuals and those with substantial comorbidities or low-performance status, while there is a reduced threshold for therapeutic intervention for relatively healthy younger individuals due to the expectation that tumor progression will inevitably necessitate proactive treatment. To treat and manage meningioma efficiently, the assessments of both neurosurgeons and radiation oncologists are essential. The possibility of other rarer tumors, including hemangiopericytomas, solitary fibrous tumors, lymphomas, metastases, melanocytic tumors, and fibrous histiocytoma, must be considered when a meningeal lesion is diagnosed, especially because the ideal diagnostic and therapeutic approaches might differ significantly in every tumor type.

Brain Invasion and Trends in Molecular Research on Meningioma

Meningiomas are the most common primary brain tumors in adults. The treatment of non-benign meningiomas remains a challenging task, and after the publication of the 2021 World Health Organization classification, the importance of molecular biological classification is emerging. In this article, we introduce the mechanisms of brain invasion in atypical meningioma and review the genetic factors involved along with epigenetic regulation. First, it is important to understand the three major steps for brain invasion of meningeal cells: 1) degradation of extracellular matrix by proteases, 2) promotion of tumor cell migration to resident cells by adhesion molecules, and 3) neovascularization and supporting cells by growth factors. Second, the genomic landscape of meningiomas should be analyzed by major categories, such as germline mutations in NF2 and somatic mutations in non-NF2 genes (TRAF7, KLF4, AKT1, SMO, and POLR2A). Finally, epigenetic alterations in meningiomas are being studied, with a focus on DNA methylation, histone modification, and RNA interference. Increasing knowledge of the molecular landscape of meningiomas has allowed the identification of prognostic and predictive markers that can guide therapeutic decision-making processes and the timing of follow-up.

A Review of the Role of Stereotactic Radiosurgery and Immunotherapy in the Management of Primary Central Nervous System Tumors

Stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICIs) are widely used in the management of brain metastases. These therapies are commonly administered concurrently; as SRS may enhance anti-tumor immunity and responsiveness to ICIs. However, the use of ICIs with and without SRS in the management of primary brain tumors remains a controversial topic. Meningiomas are the most common nonmalignant and extra-parenchymal brain tumor, which often respond well to surgery and radiotherapy. However, higher grade meningiomas tend to be resistant to these treatments, and the use of chemotherapy and targeted agents in this setting have yielded disappointing results. Thus, there is heightened interest in the utilization of ICIs. Glioblastoma is the most common malignant primary intraparenchymal brain tumor. It is associated with a grim prognosis with a median overall survival of approximately 20 months, despite optimal therapy. While SRS in the adjuvant setting, and ICI in the recurrent setting, have failed to demonstrate a survival benefit, SRS in the preoperative setting has the potential to enhance anti-tumor immunity and responsiveness to ICIs. Thus, these treatments represent an attractive option to add to the armamentarium of meningioma and glioblastoma management. In this review, we provide a detailed overview of the evidence supporting the use of ICIs and SRS in each of these settings.

Histone deacetylase inhibitors enhance oncolytic herpes simplex virus therapy for malignant meningioma

Approximately 20% of meningiomas are not benign (higher grade) and tend to relapse after surgery and radiation therapy. Malignant (anaplastic) meningioma (MM) is a minor subset of high-grade meningioma that is lethal with no effective treatment options currently. Oncolytic herpes simplex virus (oHSV) is a powerful anti-cancer modality that induces both direct cell death and anti-tumor immunity, and has shown activity in preclinical models of MM. However, clinically meaningful efficacy will likely entail rational mechanistic combination approaches. We here show that epigenome modulator histone deacetylase inhibitors (HDACi) increase anti-cancer effects of oHSV in human MM models, IOMM-Lee (NF2 wild-type) and CH157 (NF2 mutant). Minimally toxic, sub-micromolar concentrations of pan-HDACi, Trichostatin A and Panobinostat, substantively increased the infectability and spread of oHSV G47Δ within MM cells in vitro, resulting in enhanced oHSV-mediated killing of target cells when infected at low multiplicity of infection (MOI). Transcriptomics analysis identified selective alteration of mRNA processing and splicing modules that might underlie the potent anti-MM effects of combining HDACi and oHSV. In vivo, HDACi treatment increased intratumoral oHSV replication and boosted the capacity of oHSV to control the growth of human MM xenografts. Thus, our work supports further translational development of the combination approach employing HDACi and oHSV for the treatment of MM.

The role of bevacizumab for treatment-refractory intracranial meningiomas: a single institution's experience and a systematic review of the literature

INTRODUCTION

Meningiomas account for over 30% of all primary brain tumors. While surgery can be curative for these tumors, several factors may lead to a higher likelihood of recurrence. For recurrent meningiomas, bevacizumab may be considered as a therapeutic agent, but literature regarding its efficacy is sparse. Thus, we present a systematic review of the literature and case series of patients from our institution with treatment-refractory meningiomas who received bevacizumab.

METHODS

Patients at our institution who were diagnosed with recurrent meningioma between January 2000 and September 2020 and received bevacizumab monotherapy were included in this study. Bevacizumab duration and dosages were noted, as well as progression-free survival (PFS) after the first bevacizumab injection. A systematic review of the literature was also performed.

RESULTS

Twenty-three patients at our institution with a median age of 55 years at initial diagnosis qualified for this study. When bevacizumab was administered, 2 patients had WHO grade I meningiomas, 10 patients had WHO grade II meningiomas, and 11 patients had WHO grade III meningiomas. Median PFS after the first bevacizumab injection was 7 months. Progression-free survival rate at 6 months was 57%. Two patients stopped bevacizumab due to hypertension and aphasia. Systematic review of the literature showed limited ability for bevacizumab to control tumor growth.

CONCLUSION

Bevacizumab is administered to patients with treatment-refractory meningiomas and, though its effectiveness is limited, outperforms other systemic therapies reported in the literature. Further studies are required to identify a successful patient profile for utilization of bevacizumab.

Malignant anaplastic meningioma in neurofibromatosis type 1 patient: a rare case report

BACKGROUND

Meningiomas are usually associated with neurofibromatosis type 2 (NF-2), while gliomas are usually associated with neurofibromatosis type 1 (NF-1). NF-1 is an autosomal dominant genetic disorder associated with skin manifestations, bone conditions, and different types of benign and malignant tumors. Grade 3 anaplastic meningiomas are rare tumors with a poor prognosis. Systemic treatments in grade 3 meningiomas are experimental, with some reports suggestive of minimal clinical benefits. They are used occasionally for recurrent cases with no surgical or radiotherapy roles. In our case, we will focus the discussion on grade 3 anaplastic meningioma in a patient with NF-1, using chemotherapy for this aggressive, recurrent tumor. To our knowledge, this is the first case of NF-1 associated with malignant anaplastic meningioma in English literature.

CASE DESCRIPTION

In this case report, we present a 25-year-old left-handed female patient who fits the diagnostic criteria for NF-1. She presented with focal seizure and was diagnosed with grade 3 anaplastic meningioma, a highly aggressive tumor. She experienced a rapid recurrence after her initial surgery and eventually received multiple lines of treatments, including radiation and chemotherapy [temozolomide (TMZ)].

CONCLUSIONS

Systemic therapy in grade 3 meningiomas is still experimental and may have a slight clinical benefit. As a result, further prospective, multicentric studies are needed to ascertain these outcomes. Patients should be included in prospective trials because of the poor prognosis and aggressive nature of grade 3 meningiomas. In addition, discovering specific molecular biomarkers will allow us to suggest an individualized treatment. This case suggests that the differential diagnosis of a mass in a patient with NF-1 should include tumors known to be associated with the syndrome as well as sporadic, unrelated neoplasms.

Spinal meningiomas in pediatric patients – A case series and literature review

Background:

Meningiomas are the most frequent intracranial tumors in the adult population; however, they are rare in pediatric patients. In children, meningiomas often require further diagnosis of genetic comorbidities. As many as, 50% of young patients with meningiomas suffer from neurofibromatosis type 2 (NF2). Spinal meningiomas include only 10% of pediatric meningiomas.

Case Description:

Between 2000 and 2017, three children were hospitalized in the Neurosurgery Department. The patients reported prolonged periods of increasing neurological symptoms. In each case, a total gross tumor resection was performed. Histopathology result in each patient was meningioma psammomatosum. Only one girl required adjuvant radiotherapy (RTH) due to recurrent tumors. Magnetic resonance imaging (MRI) showed spinal nerves schwannomas and bilateral vestibular schwannomas in two patients with NF2.

Conclusion:

A slow tumor growth is characteristic of spinal meningiomas. Back pain is a frequent initial symptom of a slowly growing tumor mass. Subsequently, neurological deficits gradually increase. Patients require a long follow-up period and control MRI-scan. Children with diagnosed spinal meningioma should be strictly controlled because of the high risk of their developing other tumors associated with NF2. Surgical resection is the primary treatment modality of meningiomas. Adjuvant RTH should be recommended only for selected patients.

The Long and Winding Road: An Overview of the Immunological Landscape of Intracranial Meningiomas

Simple Summary

The tumor microenvironment represents the essential basis for characterizing oncological cells and supporting their growth. Along with genomic sequencing, the study of the tumor microenvironment represents a big step forward in oncological research and in the customization of treatments. Compared to gliomas, for which research has discovered greater results, the correlation between the microenvironment and tumor phenotype, and consequent prognostic implications, are still incompletely understood for intracranial meningioma. Recently, studies about the immunogenetic landscape of meningiomas have been promoted, and it is now clear that understanding the multifactorial pathogenesis of meningioma and its correlation with other specific signs (i.e., PTBE) could lead to the development of new targeted therapies, and significantly affect meningioma patients’ prognosis.

Abstract

The role of immunotherapy is gaining ever-increasing interest in the neuro-oncological field, and this is also expanding to the management of intracranial meningioma. Meningiomas are still the most common primary adult tumor of the CNS, and even though surgery and/or radiotherapy still represent cornerstones of their treatment, recent findings strongly support the potential role of specific immune infiltrate cells, their features and genomics, for the application of personalized treatments and prognostic implications. According to the PRISMA guidelines, systematic research in the most updated platform was performed in order to provide a descriptive and complete overview about the characteristics, role and potential implications of immunology in meningioma tumors. Seventy articles were included and analyzed in the present paper. The meningioma microenvironment reveals complex immune tumor-immune cells interactions that may definitely influence tumor progression, as well as offering unexpected opportunities for treatment.

Epigenetic dysregulation in meningiomas

Background

Meningiomas are the most common primary brain tumor. Though typically benign with a low mutational burden, tumors with benign histology may behave aggressively and there are no proven chemotherapies. Although DNA methylation patterns distinguish subgroups of meningiomas and have higher predictive value for tumor behavior than histologic classification, little is known about differences in DNA methylation between meningiomas and surrounding normal dura tissue.

Methods

Whole-exome sequencing and methylation array profiling were performed on 12 dura/meningioma pairs (11 WHO grade I and 1 WHO grade II). Single-nucleotide polymorphism (SNP) genotyping and methylation array profiling were performed on an additional 19 meningiomas (9 WHO grade I, 5 WHO grade II, 4 WHO grade III).

Results

Using multimodal studies of meningioma/dura pairs, we identified 4 distinct DNA methylation patterns. Diffuse DNA hypomethylation of malignant meningiomas readily facilitated their identification from lower-grade tumors by unsupervised clustering. All clusters and 12/12 meningioma-dura pairs exhibited hypomethylation of the gene promoters of a module associated with the craniofacial patterning transcription factor FOXC1 and its upstream lncRNA FOXCUT. Furthermore, we identified an epigenetic continuum of increasing hypermethylation of polycomb repressive complex target promoters with increasing histopathologic grade.

Conclusion

These findings support future investigations of the role of epigenetic dysregulation of FOXC1 and cranial patterning genes in meningioma formation as well as studies of the utility of polycomb inhibitors for the treatment of malignant meningiomas.

The Discrepancy Between Standard Histologic WHO Grading of Meningioma and Molecular Profile: A Single Institution Series

Introduction

Meningiomas are the most common primary central nervous system (CNS) tumor. They are most often benign, but a subset of these can behave aggressively. Current World Health Organization (WHO) guidelines classify meningiomas into three grades based on the histologic findings and presence or absence of brain invasion. These grades are intended to guide treatment, but meningiomas can behave inconsistently with regard to their assigned histopathological grade, influencing patient expectations and management. Advanced molecular profiling of meningiomas has led to the proposal of alternative molecular grading schemes that have shown superior predictive power. These include methylation patterns, copy number alterations, and mutually exclusive driver mutations affecting oncogenes, including BAP1, CDKN2A/B, and the TERT promoter, which are associated with particularly aggressive tumor biology. Despite the evident clinical value, advanced molecular profiling methods are not widely incorporated in routine clinical practice for meningiomas.

Objective

To assess the degree of concordance between the molecular profile of meningiomas and the histopathologic WHO classification, the current method of predicting meningioma behavior.

Methods

In a two-year single-institution experience, we used commercially available resources to determine molecular profiles of all resected meningiomas. Copy number aberrations and oncogenic driver mutations were identified and compared with the histopathologic grade.

Results

One hundred fifty-one total meningioma cases were included for analysis (85.4% WHO grade 1, 13.3% WHO grade 2, and 1.3% grade 3). Chromosomal analysis of 124 of these samples showed that 29% of WHO grade 1 tumor featured copy number profiles consistent with higher grade meningioma, and 25% of WHO grade 2 meningiomas had copy number profiles consistent with less aggressive tumors. Furthermore, 8% harbored mutations in TERT, CDKN2A/B, or BAP1 of which 6% occurred in grade 1 meningiomas.

Conclusions

Routine advanced molecular profiling of all resected meningiomas using commercially available resources allowed for identification of a significant number of meningiomas whose molecular profiles were inconsistent with WHO grade. Our work shows the clinical value of integrating routine molecular profiling with histopathologic grading to guide clinical decision making.

A multi-institutional phase II trial of bevacizumab for recurrent and refractory meningioma

Background

Systemic therapies for refractory meningiomas are limited with no FDA-approved therapeutics. Vascular endothelial growth factor (VEGF) is a signaling protein associated with neovascularization, peritumoral edema, and meningioma tumorigenesis.

Methods

This phase II study investigates the efficacy of bevacizumab (BEV), a VEGF binding monoclonal antibody, in patients with progressive Grade I (G1M), Grade II (G2M), Grade III (G3M) meningioma, and other non-parenchymal tumors including vestibular schwannoma (n = 4) and hemangiopericytoma (n = 4) with the primary endpoint of progression-free survival rate at 6-months (PFS-6). Non-meningiomas were included with the respective meningioma grade in the analysis. Secondary endpoints include median overall survival (mOS) and response rate.

Results

Fifty Patients (26 women; median age 54 years; range 23-81), 42 with progressive meningioma were treated: 10 G1M, 20 G2M, and 12 G3M. Prior treatments include surgical resection (41 patients), radiosurgery (24 patients), external beam radiotherapy (28 patients), and chemotherapy (14 patients). Median infusions administered were 16 (range, 2-68). Response was graded using the Macdonald's criteria. PFS-6, median PFS, and mOS were 87%, 22 months, 35 months for G1M; 77%, 23 months, 41 months for G2M; and 46%, 8 months, 12 months for G3M. Best radiographic responses include stable disease (G1M: 100%; G2M: 85%; G3M: 82%); partial response (G1M: 0%; G2M: 5%; G3M: 0%) and progressive disease (G1M: 0%; G2M: 10%; G3M:18%). The most common toxicities were hypertension (n = 19, 42.2%), proteinuria (n = 16, 35.6%), and fatigue (n = 14, 31.1%).

Conclusion

This study showed BEV is well tolerated and appears to be a promising systemic treatment option for patients with recurrent and refractory meningiomas.

AKT1E17K -mutated meningioma cell lines respond to treatment with the AKT inhibitor AZD5363

AIMS

Meningiomas are the most frequent primary brain tumours. Recently, knowledge about the molecular drivers underlying aggressive meningiomas has been expanded. A hotspot mutation in the AKT1 gene (AKT1^E17K ), which is found in meningiomas at the convexity and especially at the skull base, has been associated with earlier tumour recurrence.

METHODS

Here, we analysed the effects of the AKT1^E17K mutation and treatment response to the Akt inhibitor AZD5363 in transgenic meningioma cell clones and mouse xenografts modelling convexity or skull base meningiomas.

RESULTS

We show that the AKT^E17K mutation significantly enhances meningioma cell proliferation and colony size in vitro, resulting in significantly shortened survival times of mice carrying convexity or skull base AKT1^E17K xenografts. Treatment of mutant cells or xenografts (150 mg/kg/d) with AZD5363 revealed a significant decrease in cell proliferation and colony size and a prolongation of mouse survival. Western blots revealed activation of AKT1 kinase (phosphorylation at Ser273 and Thr308) by the E17K mutation in human meningioma samples and in our in vitro and in vivo models.

CONCLUSIONS

Our data suggest that AKT1^E17K mutated meningiomas are a promising selective target for AZD5363.

Exploring the role of epidermal growth factor receptor variant III in meningeal tumors

Meningioma is the second most common type of intracranial brain tumor. Immunohistochemical techniques have shown prodigious results in the role of epidermal growth factor receptor variant III (EGFR vIII) in glioma and other cancers. However, the role of EGFR vIII in meningioma is still in question. This study attempt the confer searches for the position attained by EGFR vIII in progression and expression of meningioma. Immunohistochemistry technique showed that EGFR vIII is highly expressed in benign tumors as compared to the atypical meningioma with a highly significant p-value (p<0.05). Further analysis by flow cytometry results supported these findings thus presented high intensity of EGFR vIII in low grades of meningioma. The study revealed that the significant Ki 67 values, to predictor marker for survival and prognosis of the patients. Higher expression of EGFR vIII in low grades meningiomas as compared to high-grade tumors indicate towards its oncogenic properties. To our knowledge, limited studies reported in literature expressing the EGFR vIII in meningioma tumors. Hence, Opinions regarding the role that EGFR vIII in tumorigenesis and tumor progression are clearly conflicting and, therefore, it is crucial not only to find out its mechanism of action, but also to definitely identify its role in meningioma.

Medical management of meningiomas

Meningiomas are the most frequently occurring primary brain tumors in adults, representing almost one-third of all primary central nervous system tumors. Several factors have been suggested as an underlying cause in the development of meningiomas, such as ionizing radiation (therapeutic or other incidental exposure), hormonal factors, and genetic predisposition syndromes. Other established factors associated with meningiomas include age, female gender, and those from non-Hispanic Black backgrounds. Though the 2016 World Health Organization Classification of Brain Tumors largely preserves the existing grading scheme for organization of meningioma, there is increasing understanding of the molecular factors underlying the development of meningioma, some of which now form the basis for active clinical investigation. The mainstay of treatment has been the combination of radiation therapy and surgery, with a limited role for systemic therapy due to low efficacy, short duration of treatment response, and lack of uniform response criteria. Similar to other primary and metastatic brain tumors, immune-based therapies hold promise and are still under investigation.

Meningioma: A Review of Epidemiology, Pathology, Diagnosis, Treatment, and Future Directions

Meningiomas are the most common intracranial tumor, making up more than a third of all primary central nervous system (CNS) tumors. They are mostly benign tumors that can be observed or preferentially treated with gross total resection that provides good outcomes. Meningiomas with complicated histology or in compromising locations has proved to be a challenge in treating and predicting prognostic outcomes. Advances in genomics and molecular characteristics of meningiomas have uncovered potential use for more accurate grading and prediction of prognosis and recurrence. With the study and detection of genomic aberrancies, specific biologic targets are now being trialed for possible management of meningiomas that are not responsive to standard surgery and radiotherapy treatment. This review summarizes current epidemiology, etiology, molecular characteristics, diagnosis, treatments, and current treatment trials.

A Practical Overview on the Molecular Biology of Meningioma

PURPOSE OF REVIEW

Meningioma is a common intracranial neoplasm currently classified in 15 histologic subtypes across 3 grades of malignancy. First-choice therapy for meningioma is maximum safe resection for grade I tumors, and surgery plus optional and mandatory adjuvant radiotherapy for grade II and III, respectively, given the increased rate of recurrence even in the event of complete resection. The WHO 2016 histopathologic grading of meningioma has been questioned due to subjectivity and its controversial predictive power for recurrence.

RECENT FINDINGS

Novel DNA methylation profiling has simplified classification into six classes that seem to improve prognostic accuracy. We review five main topics of molecular biology research regarding tumorigenesis and natural history of meningioma from the clinician's perspective: the histopathologic diagnostic features and pitfalls of the current tumor classification; the molecular integrated diagnosis supported by identification of genetic alterations and DNA methylation profiling; the general landscape of the various signaling pathways involved in meningioma formation; the pathogenic theories of the peri-tumoral edema present in meningioma and its therapy implications; and a summarized review on the current treatments and plausible targeted therapies directed to meningioma. It seems likely that molecular assessment will be introduced within the next update of the WHO classification of meningiomas, acknowledging the promising value of DNA methylation profiling. This integrated diagnostic protocol will simplify tumor subtype categorization and provide improved accuracy in predicting recurrence and outcome. Although much effort is being done in identifying key gene mutations, and elucidating specific intracellular signaling pathways involved in meningioma tumorigenesis, effective targeted therapies for recurrent meningiomas are still lacking.

Multiplatform genomic profiling and magnetic resonance imaging identify mechanisms underlying intratumor heterogeneity in meningioma

Meningiomas are the most common primary intracranial tumors, but the molecular drivers of meningioma tumorigenesis are poorly understood. We hypothesized that investigating intratumor heterogeneity in meningiomas would elucidate biologic drivers and reveal new targets for molecular therapy. To test this hypothesis, here we perform multiplatform molecular profiling of 86 spatially-distinct samples from 13 human meningiomas. Our data reveal that regional alterations in chromosome structure underlie clonal transcriptomic, epigenomic, and histopathologic signatures in meningioma. Stereotactic co-registration of sample coordinates to preoperative magnetic resonance images further suggest that high apparent diffusion coefficient (ADC) distinguishes meningioma regions with proliferating cells enriched for developmental gene expression programs. To understand the function of these genes in meningioma, we develop a human cerebral organoid model of meningioma and validate the high ADC marker genes CDH2 and PTPRZ1 as potential targets for meningioma therapy using live imaging, single cell RNA sequencing, CRISPR interference, and pharmacology.

Basis for Immunotherapy for Treatment of Meningiomas

Meningiomas are common tumors that account for approximately one third of CNS tumors diagnosed every year. They are classified by the World Health Organization in grades I-III. Higher grades have an increased rate of growth, invasiveness, rate of recurrence, and worse outcomes than lower grades. Most meningiomas are grade I, while ~18% of meningiomas are grade II and III in hospital-based series. Meningiomas are typically "benign" tumors that are treated with surgery and radiation. However, when they recur or are unresectable, treatment options are very limited, especially since they are chemotherapy-resistant. Recent advances in the treatment of cancers with immunotherapy have focused on checkpoint blockade as well as other types of immunotherapy. There is emerging evidence supporting the use of immunotherapy as a potentially effective treatment strategy for meningioma patients. The immune microenvironment of meningiomas is a complex interplay of genetic alterations, immunomodulatory protein expression, and tumor-immune cell interactions. Meningiomas are known to be infiltrated by immune cells including microglia, macrophages, B-cells, and T-cells. Several mechanisms contribute to decreased an ti-tumor immune response, allowing tumor growth and evasion of the immune system. We discuss the most current knowledge on the immune micro-environment of meningiomas, preclinical findings of immunotherapy in meningiomas, meningioma immunotherapy clinical trials, and also offer insight into future prospects for immunotherapies in meningiomas.

Advances in multidisciplinary therapy for meningiomas

Surgery has long been established as the first-line treatment for the majority of symptomatic and enlarging meningiomas, and evidence for its success is derived from retrospective case series. Despite surgical resection, a subset of meningiomas display aggressive behavior with early recurrences that are difficult to treat. The decision to radically resect meningiomas and involved structures is balanced against the risk for neurological injury in patients. Radiation therapy has largely been used as a complementary and safe therapeutic strategy in meningiomas with evidence primarily stemming from retrospective, single-institution reports. Two of the first cooperative group studies (RTOG 0539 and EORTC 22042) evaluating the outcomes of adjuvant radiation therapy in higher-risk meningiomas have shown promising preliminary results. Historically, systemic therapy has resulted in disappointing results in meningiomas. However, several clinical trials are under way evaluating the efficacy of chemotherapies, such as trabectedin, and novel molecular agents targeting Smoothened, AKT1, and focal adhesion kinase in patients with recurrent meningiomas.

The Role of Adjuvant Treatment in Craniofacial Malignancy: A Critical Review

Background: Tumors originating from the craniofacial region usually present in a locally advanced stage with frequent involvement of adjacent sites and have a strong tendency for local recurrence in the absence of adjuvant therapy, even when the original surgical resection was presumed to be radical. In the past decades, several advances in the radiological diagnosis and treatment of craniofacial malignancies have been introduced. There are, however, no randomized trials that define the optimal multimodal treatment of these tumors because of their rarity as well as heterogeneity in both histology and site of origin. The aim of this study was to conduct a critical review of the role of adjuvant therapy in the treatment of craniofacial malignancy. Method: We conducted a critical review of the past and contemporary literature available, focusing on adjuvant oncological treatments of the most common craniofacial malignancies. Results: Preoperative radiotherapy can have a documented role in the treatment of olfactory neuroblastoma and soft tissue sarcoma, while preoperative chemotherapy can be advocated in the treatment of sinonasal undifferentiated carcinoma, neuroendocrine carcinoma, olfactory neuroblastoma, and craniofacial sarcoma (both soft-tissue and high-grade osteosarcoma). Postoperative radiotherapy has a well-established role in the treatment of most craniofacial malignancies. The role of postoperative chemotherapy is unclear in most histologies, but is commonly used during the treatment of well-selected cases of paranasal sinus carcinoma, olfactory neuroblastoma, mucosal melanoma, soft tissue sarcoma and high-grade craniofacial osteosarcoma. Discussion: Alongside developments in surgery, there have also been improvements in diagnostics, radiotherapy, and chemotherapy. Implementation of novel radiation techniques allows delivery of higher radiation doses while minimizing irradiation-related morbidity. Better understanding of tumor biology allows the construction of more complex treatment strategies, incorporating adjuvant chemotherapy either pre- or postoperatively. In the era of personalized targeted therapy, rapid strides are being made to identify specific tumor-targets for use of novel biologic agents, with the potential to change current management paradigms.

Characterization and comparison of genomic profiles between primary cancer cell lines and parent atypical meningioma tumors

Background

Meningiomas are the second most common primary tumors of the central nervous system. However, there is a paucity of data on meningioma biology due to the lack of suitable preclinical in vitro and in vivo models. In this study, we report the establishment and characterization of patient-derived, spontaneously immortalized cancer cell lines derived from World Health Organization (WHO) grade I and atypical WHO grade II meningiomas.

Methods

We evaluated high-resolution 3T MRI neuroimaging findings in meningioma patients which were followed by histological analysis. RT-qPCR and immunostaining analyses were performed to determine the expression levels of meningioma-related factors. Additionally, flow cytometry and sorting assays were conducted to investigate and isolate the CD133 and CD44 positive cells from primary atypical meningioma cells. Further, we compared the gene expression profiles of meningiomas and cell lines derived from them by performing whole-exome sequencing of the blood and tumor samples from the patients, and the primary cancer cell lines established from the meningioma tumor.

Results

Our results were consistent with earlier studies that reported mutations in NF2, SMO, and AKT1 genes in atypical meningiomas, and we also observed mutations in MYBL2, a gene that was recently discovered. Significantly, the genomic signature was consistent between the atypical meningioma cancer cell lines and the tumor and blood samples from the patient.

Conclusion

Our results lead us to conclude that established meningioma cell lines with a genomic signature identical to tumors might be a valuable tool for understanding meningioma tumor biology, and for screening therapeutic agents to treat recurrent meningiomas.

Advances in Molecular Classification and Therapeutic Opportunities in Meningiomas

PURPOSE OF REVIEW

Our understanding of the genetic and epigenetic alterations in meningioma and the underlying tumor biology of meningioma has significantly changed over the past decade and resulted in revision of prognostically relevant meningioma subclasses within and beyond the WHO classification of CNS tumors.

RECENT FINDINGS

The 2016 WHO classification of CNS tumors recognizes WHO grade I, II, and III based on histopathological features. Recent work has identified genetic alterations with prognostic implications, including mutations of the TERT promoter, loss of function of the DMD gene, and inactivation of the tumor suppressor BAP-1. Studies of DNA methylation patterns in meningiomas have resulted in a novel and prognostically relevant meningioma subclassification schema. There have been major advances in our understanding of prognostically relevant genetic and epigenetic changes in meningioma which will hopefully allow for improvement in clinical trial design and the development of more effective therapies for meningioma.

Multi-parametric qualitative and quantitative MRI assessment as predictor of histological grading in previously treated meningiomas

PURPOSE

Meningiomas are mainly benign tumors, though a considerable proportion shows aggressive behaviors histologically consistent with atypia/anaplasia. Histopathological grading is usually assessed through invasive procedures, which is not always feasible due to the inaccessibility of the lesion or to treatment contraindications. Therefore, we propose a multi-parametric MRI assessment as a predictor of meningioma histopathological grading.

METHODS

Seventy-three patients with 74 histologically proven and previously treated meningiomas were retrospectively enrolled (42 WHO I, 24 WHO II, 8 WHO III) and studied with MRI including T2 TSE, FLAIR, Gradient Echo, DWI, and pre- and post-contrast T1 sequences. Lesion masks were segmented on post-contrast T1 sequences and rigidly registered to ADC maps to extract quantitative parameters from conventional DWI and intravoxel incoherent motion model assessing tumor perfusion. Two expert neuroradiologists assessed morphological features of meningiomas with semi-quantitative scores.

RESULTS

Univariate analysis showed different distributions (p < 0.05) of quantitative diffusion parameters (Wilcoxon rank-sum test) and morphological features (Pearson's chi-square; Fisher's exact test) among meningiomas grouped in low-grade (WHO I) and higher grade forms (WHO II/III); the only exception consisted of the tumor-brain interface. A multivariate logistic regression, combining all parameters showing statistical significance in the univariate analysis, allowed discrimination between the groups of meningiomas with high sensitivity (0.968) and specificity (0.925). Heterogeneous contrast enhancement and low ADC were the best independent predictors of atypia and anaplasia.

CONCLUSION

Our multi-parametric MRI assessment showed high sensitivity and specificity in predicting histological grading of meningiomas. Such an assessment may be clinically useful in characterizing lesions without histological diagnosis. Key points • When surgery and biopsy are not feasible, parameters obtained from both conventional and diffusion-weighted MRI can predict atypia and anaplasia in meningiomas with high sensitivity and specificity. • Low ADC values and heterogeneous contrast enhancement are the best predictors of higher grade meningioma.

Proposed response assessment and endpoints for meningioma clinical trials: report from the Response Assessment in Neuro-Oncology Working Group

No standard criteria exist for assessing response and progression in clinical trials involving patients with meningioma, and there is no consensus on the optimal endpoints for trials currently under way. As a result, there is substantial variation in the design and response criteria of meningioma trials, making comparison between trials difficult. In addition, future trials should be designed with accepted standardized endpoints. The Response Assessment in Neuro-Oncology Meningioma Working Group is an international effort to develop standardized radiologic criteria for treatment response for meningioma clinical trials. In this proposal, we present the recommendations for response criteria and endpoints for clinical trials involving patients with meningiomas.

Response assessment of meningioma: 1D, 2D, and volumetric criteria for treatment response and tumor progression

BACKGROUND

Meningiomas are the most common primary brain tumors in adults. Due to their variable growth rates and irregular tumor shapes, response assessment in clinical trials remains challenging and no standard criteria have been defined. We evaluated 1D, 2D, and volume imaging criteria to assess whether a volumetric approach might be a superior surrogate for overall survival (OS).

METHODS

In this retrospective multicenter study, we evaluated the clinical and imaging data of 93 patients with recurrent meningiomas treated with pharmacotherapy. One-dimensional (1D), 2D, and volumetric measurements of enhancing tumor on pre- and post-treatment MRI were compared at 6 and 12 months after treatment initiation. Cox proportional hazards models were used to examine the relationship between each imaging criterion and OS.

RESULTS

The median age of the patient cohort is 51 years (range 12-88), with 14 World Health Organization (WHO) grade I, 53 WHO grade II, and 26 WHO grade III meningiomas. Volumetric increase of 40% and unidimensional increase by 10 mm at 6 months and 12 months provided the strongest association with overall survival (HR = 2.58 and 3.24 respectively, p<0.01). Setting a volume change threshold above 40% did not correlate with survival. The interobserver agreement of 1D, 2D, and volume criteria is only moderate (kappa = 0.49, 0.46, 0.52, respectively). None of the criteria based on tumor size reduction were associated with OS (P > 0.09).

CONCLUSION

Compared with 1D (Response Evaluation Criteria In Solid Tumors 1.1) and 2D (Response Assessment in Neuro-Oncology) approaches, volumetric criteria for tumor progression has a stronger association with OS, although the differences were only modest. The interobserver variability is moderate for all 3 methods. Further validation of these findings in an independent patient cohort is needed.

The controversial role of Bevacizumab in the treatment of patients with intracranial meningioma: a comprehensive literature review

Introduction: Meningiomas represent the most common primary intracranial tumors. Today, surgical resection, followed by radiotherapy when indicated, is still the treatment of choice. In recent years, distinct oncogenic pathways have been identified, laying the foundations of new personalized targeted therapies.Areas covered: The aim of this study was to highlight the effects, complications, possible associations with other therapeutic approaches and multi-parametric outcome evaluation of Bevacizumab for the treatment of meningiomas. A literature review according to PRISMA criteria regarding the role of Bevacizumab for the treatment of various WHO grades of meningiomas was performed. 15 relevant papers, including 6 retrospective clinical trial series, 3 prospective trials, and 6 single patient case reports for a total of 134 patients and 211 meningiomas were include.Expert opinion: Because of the lack of strong clinical evidence about improved survival and related toxicity, the use of Bevacizumab for the treatment of meningiomas should be carefully evaluated. Further exploration, ideally with randomized controlled trials, is needed to better define the role of this drug in the treatment of meningiomas.

Subcutaneous Metastasis of Atypical Meningioma: Case Report and Literature Review

BACKGROUND

Meningioma, a neoplasm of the meninges, is usually a benign localized tumor. Extraneural metastasis is an extremely rare complication of meningiomas, and only a few cases have been reported to date. The present study reports a case of scalp metastasis of an atypical meningioma and discusses the types of atypical meningiomas and their management options.

CASE DESCRIPTION

A 69-year-old man presented with scalp metastasis of an atypical meningioma. Six years after the right frontoparietal meningioma lesion was completely resected, an isolated subcutaneous metastasis developed at the right frontal region of the scalp, originating at the scar left by the first surgery. Postoperative histologic examination of the subcutaneous tumor revealed the features of an atypical meningioma.

CONCLUSIONS

This study highlights that resection of meningiomas is still associated with a risk of iatrogenic metastasis. Surgeons should carefully wash out the operative field and change surgical tools frequently to avoid the potential risk of metastasis.

The CREB-binding protein inhibitor ICG-001: a promising therapeutic strategy in sporadic meningioma with NF2 mutations

Background

Meningiomas with Neurofibromin 2 gene mutations (NF2-mutant meningiomas) account for ~40% of the sporadic meningiomas. However, there is still no effective drug treatment for the disease.

Methods

Expression profile of Merlin protein was explored through immunohistochemistry in a meningioma patient cohort (n = 346). A 20-agent library covering a wide range of meningioma relevant targets was tested using meningioma cell lines IOMM-Lee (NF2 wildtype) and CH157-MN (NF2 deficient). Therapeutic effects and biological mechanisms of the identified compound, ICG-001, in NF2-mutant meningiomas were further characterized in vitro and in patient-derived xenograft (PDX) models.

Results

Low Merlin expression was associated with meningioma proliferation and poor clinical outcomes in a large patient series. ICG-001, a cAMP-responsive element binding (CREB)-binding protein (CBP) inhibitor, selectively suppressed tumor growth of cells with low Merlin expression. Besides, ICG-001 mediated CH157-MN and IOMM-Lee growth inhibition primarily through robust induction of the G1 cell-cycle arrest. Treatment with ICG-001 alone significantly reduced the growth of NF2-mutant xenografts in mice, as well. We also provide further evidence that ICG-001 inhibits proliferation of NF2-mutant meningioma cells at least partly through attenuating the FOXM1-mediated Wnt/β-catenin signaling.

Conclusions

This study highlights the importance of ligand-mediated Wnt/β-catenin signaling as well as its drugable potency in NF2-mutant meningioma.

Differentiating microcystic meningioma from atypical meningioma using diffusion-weighted imaging

PURPOSE

Microcystic meningioma (MCM) appears similar to atypical meningioma(AM) as per conventional diagnostic imaging. However, considering their different recurrence rate and prognosis, accurate differential diagnosis is essential for determine the appropriate treatment strategy. The aim of the study was to differentiate MCM from AM by diffusion-weighted imaging (DWI), in order to provide the basis for accurate preoperative diagnosis.

METHODS

The preoperative clinical data, conventional MRI and DWI data of 15 MCM and 30 AM cases were retrospectively analyzed. The average apparent diffusion coefficient (ADC_mean), minimum ADC (ADC_min) and normalized ADC (nADC) between MCM and AM were compared using two sample t-tests. The value of ADC_mean, ADC_min and nADC in the differential diagnosis of MCM and AM were calculated by the receiver operating curve (ROC) analysis.

RESULTS

The ADC_mean (1.06 ± 0.10 vs 0.80 ± 0.11 × 10^-3 mm²/s; P < 0.001), ADC_min (0.99 ± 0.10 vs 0.74 ± 0.12 × 10^-3 mm²/s; P < 0.001) and nADC (1.45 ± 0.17 vs 1.07 ± 0.17; P < .0001) were significantly higher in MCM compared to AM. ADC_mean of 0.91 × 10^-3 mm²/s showed an optimum area under the ROC curve of 0.967 ± 0.022, and distinguished between MCM and AM with 86.67% sensitivity, 100% specificity and 88.89% accuracy. In addition, its positive and negative predictive values were 96.29% and 77.78% respectively.

CONCLUSIONS

DWI can differentially diagnose MCM and AM, and ADC_mean is a potential quantitative tool that can improve preoperative diagnosis of both tumors.

Everolimus and Octreotide for Patients with Recurrent Meningioma: Results from the Phase II CEVOREM Trial

PURPOSE

Aggressive meningiomas that progress after surgery/radiotherapy represent an unmet medical need. Strong and constant expression of SSTR2A receptors and activation of the Pi3K/Akt/mTOR pathway have been demonstrated in meningiomas. The combination of everolimus, an mTOR inhibitor, and octreotide, a somatostatin agonist, has shown additive antitumor effect in vitro. The phase II CEVOREM trial investigated the efficacy of this combination on recurrent meningiomas.

PATIENTS AND METHODS

Patients with documented recurrent tumor progression ineligible for further surgery/radiotherapy were eligible to receive octreotide (30 mg/d, day 1) and everolimus (10 mg/d, days 1-28). The primary endpoint was the 6-month progression-free survival rate (PFS6). The secondary endpoints were overall survival, response rate, tumor growth rate according to central review, and safety.

RESULTS

A total of 20 patients were enrolled, including 2 with World Health Organization (WHO) grade I tumors, 10 with WHO grade II tumors, and 8 with WHO grade III tumors; furthermore, 4 patients harbored NF2 germline mutation. The overall PFS6 was 55% [95% confidence interval (CI), 31.3%-73.5%], and overall 6- and 12-month survival rates were 90% (95% CI, 65.6%-97.4%) and 75% (95% CI, 50.0%-88.7%), respectively. A major decrease (>50%) was observed in the growth rate at 3 months in 78% of tumors. The median tumor growth rate decreased from 16.6%/3 months before inclusion to 0.02%/3 months at 3 months (P < 0.0002) and 0.48%/3 months at 6 months after treatment (P < 0.0003).

CONCLUSIONS

The combination of everolimus and octreotide was associated with clinical and radiological activity in aggressive meningiomas and warrants further studies. Decrease in the tumor volume growth rate should be considered a complementary and sensitive endpoint to select potentially effective drugs for recurrent meningiomas.

Meningiomas in children

Meningiomas in children are poorly understood because they are rare. Recent reports have provided a more complete description of their incidence, genetics, imaging features, and outcome. In general, meningiomas in children are more likely to be higher grade, present in atypical locations, and have a higher risk of recurrence. The challenges encountered in children with respect to surgical and postoperative management are unique. Improved understanding of pediatric meningiomas, as well as the availability of new surgical, medical, and radiation therapies, creates opportunities to improve outcomes in this unique population.

Comprehensive Molecular Profiling Identifies FOXM1 as a Key Transcription Factor for Meningioma Proliferation

Meningioma is the most common primary intracranial tumor, but the molecular drivers of aggressive meningioma are incompletely understood. Using 280 human meningioma samples and RNA sequencing, immunohistochemistry, whole-exome sequencing, DNA methylation arrays, and targeted gene expression profiling, we comprehensively define the molecular profile of aggressive meningioma. Transcriptomic analyses identify FOXM1 as a key transcription factor for meningioma proliferation and a marker of poor clinical outcomes. Consistently, we discover genomic and epigenomic factors associated with FOXM1 activation in aggressive meningiomas. Finally, we define a FOXM1/Wnt signaling axis in meningioma that is associated with a mitotic gene expression program, poor clinical outcomes, and proliferation of primary meningioma cells. In summary, we find that multiple molecular mechanisms converge on a FOXM1/Wnt signaling axis in aggressive meningioma.

Using multiplatform molecular profiling, Vasudevan et al. comprehensively define the molecular profile of aggressive meningioma. They identify genomic, epigenomic, and transcriptomic mechanisms that converge on a FOXM1/Wnt signaling axis in aggressive meningioma that is associated with meningioma cell proliferation and is a marker of poor clinical outcomes across molecular subgroups.

Medical management of meningioma in the era of precision medicine

Surgery is curative for most meningiomas, but a minority of these tumors recur and progress after resection. Initial trials of medical therapies for meningioma utilized nonspecific cytotoxic chemotherapies. The presence of hormone receptors on meningioma ushered in trials of hormone-mimicking agents. While these trials expanded clinical understanding of meningioma, they ultimately had limited efficacy in managing aggressive lesions. Subsequent detection of misregulated proteins and genomic aberrancies motivated the study of therapies targeting specific biological disturbances observed in meningioma. These advances led to trials of targeted kinase inhibitors and immunotherapies, as well as combinations of these agents together with chemotherapies. Prospective trials currently recruiting participants are testing a diverse range of medical therapies for meningioma, and some studies now require the presence of a specific protein alteration or genetic mutation as an inclusion criterion. Increasing understanding of the unique and heterogeneous nature of meningiomas will continue to spur the development of novel medical therapies for the arsenal against aggressive tumors.

The Prognostic Value of Pretreatment Gallium-68 DOTATATE Positron Emission Tomography/Computed Tomography in Irradiated Non-benign Meningioma

Purpose of the study:

The purpose of this study was to evaluate the potential value of gallium-68 (Ga-68)-DOTATATE positron emission tomography/computed tomography (PET/CT) in predicting the risk of progression in nonbenign meningioma after definite irradiation. We retrospectively reviewed our patients with meningiomas who had the highest risk of progression: WHO histological Grade II and III tumors and with macroscopic disease as identified in Ga-68-DOTATATE PET/CT.

Materials and Methods:

Thirteen patients were included in this study. For each tumor, the following quantifiers were measured: maximum and mean standardized uptake volume (SUV), standard deviation, metabolic tumor volume (MTV), total lesion activity, and coefficient of variation. Each of the quantifiers except for maximum SUV was obtained with three different SUV thresholds: muscle based (_ms), liver based (_liv), and gradient based (_gb). The quantifiers were analyzed in univariate Cox model for their prognostic value for progression-free survival (PFS) and overall survival (OS).

Results:

Mean follow-up of the patients was 28.2 months. The 2-year PFS and OS was 28.1% and 76.9%, respectively. The MTV_gb was a significant predictor for PFS (risk of progression of disease above vs. below the 34 cm³ threshold: 100% vs. 28.3%, P = 0.0003). Clinically, the male sex also influenced PFS (Hazard ratio =13.06; 95% confidence interval: 1.56–109.25; P = 0.018). The mean SUV_ms(P = 0.041) and SUV_gb(P = 0.048) had a prognostic value for predicting the risk of death.

Conclusion:

Ga-68-DOTATATE PET/CT has potential to predict disease progression in nonbenign meningioma patients. Further prospective studies for validating and standardizing these findings are indicated.

Immunological and vascular characteristics in cavernous sinus meningioma

OBJECTIVES

It is difficult to treat cavernous sinus (CS) meningiomas because of their complex vascular and neurological structures. Recently, immunotherapy has become an attractive therapeutic modality, but the role of tumor immune microenvironment is yet to be investigated for CS meningiomas. In the current study, these molecular and histopathological characteristics were examined in CS meningiomas.

METHODS

The present study used twenty-eight meningioma tissues arising in two different locations (8 CS and 20 convexity meningiomas). Immunohistochemical analyses were performed with CD3, CD4, CD8, Foxp3, CD163, PDGFR-β, VEGF receptors 1 & 2 (VEGFR-1, VEGFR-2), VEGF-A and HIF-1α. Quantitative polymerase chain reaction (qPCR) was performed to assess the expression of Foxp3, VEGF-A, CD163, VEGFRs-1 & 2 and HIF-1α.

RESULTS

The numbers of different tumor-infiltrating immune cells, such as immunosuppressive cells, were significantly lower in CS meningiomas compared with convexity meningiomas. Analysis of the vascular characteristics showed the vessels in the CS meningiomas were covered with PDGFR-β-positive pericytes and were negative or had only very low amounts of VEGFR-1 and VEGFR-2. However, most vessels in convexity meningiomas showed high VEGFRs expression and were not covered with pericytes. Immunohistochemical and qPCR analyses revealed that the expression of HIF-1α, VEGF-A and VEGFRs-1 & 2 was lower in CS meningiomas.

CONCLUSION

Fewer immunocompetent cells were observed in CS meningiomas compared with convexity meningiomas. Lower expression of VEGF-A, VEGFRs-1 and 2, and the vascular structure may contribute to this specific immune microenvironment.

New molecular targets in meningiomas: the present and the future

PURPOSE OF REVIEW

Meningiomas, the most common primary brain tumor, have historically been managed with surgery and radiation. Traditional chemotherapy has not been effective. Fortunately, recent advances in genetic sequencing have led to an improved understanding of the molecular drivers in meningioma. This article aims to discuss the diagnostic and therapeutic implications of recently discovered genetic alterations in meningiomas.

RECENT FINDINGS

Many of the recently discovered genetic alterations correlate with distinct clinical phenotypes. SMO, AKT and PIK3CA mutations are enriched in the anterior skull base. KLF4 mutations are specific for secretory histology, and BAP1 alterations are common in progressive rhabdoid meningiomas. Alterations in TERT, DMD and BAP1 correlate with poor clinical outcomes. Importantly, the discovery of clinically actionable alterations in a number of genes, including SMO, AKT1 and PIK3CA, has opened up novel potential avenues for therapeutic management of meningiomas. Overexpression of PD-L1 in higher grade meningiomas also provides preclinical support for the investigation of checkpoint blockade.

SUMMARY

The discovery of genetic alterations has improved our understanding of the natural history and classification of meningiomas. Clinical trials with several novel agents targeting driver mutations are currently accruing patients and they can lead to better treatment strategies.