Systemic and local immunosuppression in patients with high-grade meningiomas

MRI features and tumor-infiltrating CD8 + T cells-based nomogram for predicting meningioma recurrence risk

OBJECTIVE

This study was based on MRI features and number of tumor-infiltrating CD8 + T cells in post-operative pathology, in predicting meningioma recurrence risk.

METHODS

Clinical, pathological, and imaging data of 102 patients with surgically and pathologically confirmed meningiomas were retrospectively analyzed. Patients were divided into recurrence and non-recurrence groups based on follow-up. Tumor-infiltrating CD8 + T cells in tissue samples were quantitatively assessed with immunohistochemical staining. Apparent diffusion coefficient (ADC) histogram parameters from preoperative MRI were quantified in MaZda. Considering the high correlation between ADC histogram parameters, we only chose ADC histogram parameter that had the best predictive efficacy for COX regression analysis further. A visual nomogram was then constructed and the recurrence probability at 1- and 2-years was determined. Finally, subgroup analysis was performed with the nomogram.

RESULTS

The risk factors for meningioma recurrence were ADCp1 (hazard ratio [HR] = 0.961, 95% confidence interval [95% CI]: 0.937 ~ 0.986, p = 0.002) and CD8 + T cells (HR = 0.026, 95%CI: 0.001 ~ 0.609, p = 0.023). The resultant nomogram had AUC values of 0.779 and 0.784 for 1- and 2-years predicted recurrence rates, respectively. The survival analysis revealed that patients with low CD8 + T cells counts or ADCp1 had higher recurrence rates than those with high CD8 + T cells counts or ADCp1. Subgroup analysis revealed that the AUC of nomogram for predicting 1-year and 2-year recurrence of WHO grade 1 and WHO grade 2 meningiomas was 0.872 (0.652) and 0.828 (0.751), respectively.

CONCLUSIONS

Preoperative ADC histogram parameters and tumor-infiltrating CD8 + T cells may be potential biomarkers in predicting meningioma recurrence risk.

CLINICAL RELEVANCE STATEMENT

The findings will improve prognostic accuracy for patients with meningioma and potentially allow for targeted treatment of individuals who have the recurrent form.

Immune cell infiltration and inflammatory landscape in primary brain tumours

BACKGROUND

Primary malignant brain tumours are more than one-third of all brain tumours and despite the molecular investigation to identify cancer driver mutations, the current therapeutic options available are challenging due to high intratumour heterogeneity. In addition, an immunosuppressive and inflammatory tumour microenvironment strengthens cancer progression. Therefore, we defined an immune and inflammatory profiling of meningioma and glial tumours to elucidate the role of the immune infiltration in these cancer types.

METHODS

Using tissue microarrays of 158 brain tumour samples, we assessed CD3, CD4, CD8, CD20, CD138, Granzyme B (GzmB), 5-Lipoxygenase (5-LOX), Programmed Death-Ligand 1 (PD-L1), O-6-Methylguanine-DNA Methyltransferase (MGMT) and Transglutaminase 2 (TG2) expression by immunohistochemistry (IHC). IHC results were correlated using a Spearman correlation matrix. Transcript expression, correlation, and overall survival (OS) analyses were evaluated using public datasets available on GEPIA2 in Glioblastoma (GBM) and Lower Grade Glioma (LGG) cohorts.

RESULTS

Seven out of ten markers showed a significantly different IHC expression in at least one of the evaluated cohorts whereas CD3, CD4 and 5-LOX were differentially expressed between GBMs and astrocytomas. Correlation matrix analysis revealed that 5-LOX and GzmB expression were associated in both meningiomas and GBMs, whereas 5-LOX expression was significantly and positively correlated to TG2 in both meningioma and astrocytoma cohorts. These findings were confirmed with the correlation analysis of TCGA-GBM and LGG datasets. Profiling of mRNA levels indicated a significant increase in CD3 (CD3D, CD3E), and CD138 (SDC1) expression in GBM compared to control tissues. CD4 and 5-LOX (ALOX5) mRNA levels were significantly more expressed in tumour samples than in normal tissues in both GBM and LGG. In GBM cohort, GzmB (GZMB), SDC1 and MGMT gene expression predicted a poor overall survival (OS). Moreover, in LGG cohort, an increased expression of CD3 (CD3D, CD3E, CD3G), CD8 (CD8A), GZMB, CD20 (MS4A1), SDC1, PD-L1, ALOX5, and TG2 (TGM2) genes was associated with worse OS.

CONCLUSIONS

Our data have revealed that there is a positive and significant correlation between the expression of 5-LOX and GzmB, both at RNA and protein level. Further evaluation is needed to understand the interplay of 5-LOX and immune infiltration in glioma progression.

Volumetric growth rate of incidentally found meningiomas on immunotherapy

PURPOSE

The expression of PD-L1 in high-grade meningiomas made it a potential target for immunotherapy research in refractory cases. Several prospective studies in this field are still on going. We sought to retrospectively investigate the effects of check-point inhibitors (CI) on meningiomas that had been naïve to either surgical or radiation approaches by following incidental meningiomas found during treatment with CI for various primary metastatic cancers.

METHODS

We used the NYU Perlmutter Cancer Center Data Hub to find patients treated by CI for various cancers, who also had serial computerized-tomography (CT) or magnetic-resonance imaging (MRI) reports of intracranial meningiomas. Meningioma volumetric measurements were compared between the beginning and end of the CI treatment period. Patients treated with chemotherapy during this period were excluded.

RESULTS

Twenty-five patients were included in our study, of which 14 (56%) were on CI for melanoma, 5 (20%) for non-small-cell lung cancer and others. CI therapies included nivolumab (n = 15, 60%), ipilimumab (n = 11, 44%) and pembrolizumab (n = 9, %36), while 9 (36%) were on ipilimumab/nivolumab combination. We did not find any significant difference between tumor volumes before and after treatment with CI (1.31 ± 0.46 vs. 1.34 ± 0.46, p=0.8, respectively). Among patients beyond 1 year of follow-up (n = 13), annual growth was 0.011 ± 0.011 cm3/year. Five patients showed minor volume reduction of 0.12 ± 0.10 cm3 (21 ± 6% from baseline). We did not find significant predictors of tumor volume reduction.

CONCLUSION

Check-point inhibitors may impact the natural history of meningiomas. Additional research is needed to define potential clinical indications and treatment goals.

Interdisciplinary Therapeutic Approaches to Atypical and Malignant Meningiomas

Meningiomas have the highest incidence among brain tumors. In contrast to benign tumors that constitute the majority of this tumor entity, the treatment of aggressive meningiomas (WHO Grade 2 and 3) is more challenging, requiring gross total removal of the tumor and the affected dura and adjuvant radiotherapy. Sometimes the location and/or the configuration of the tumor do not favor radical surgical resection without endangering the patient's clinical condition after surgery and pharmacological therapy has, until now, not been proven to be a reliable alternative. Discussion: In this narrative review, we discuss the current literature with respect to the management of meningiomas, discussing the importance of the grade of resection in the overall prognosis of the patient and in the planning of adjuvant therapy. Conclusions: According to the location and size of the tumor, radical resection should be taken into consideration. In patients with aggressive meningiomas, adjuvant radiotherapy should be performed after surgery. In cases of skull base meningiomas, a maximal, though safe, resection should take place before adjuvant therapy. An interdisciplinary approach is beneficial for patients with primary or recurrent meningioma.

Medical Management of Meningiomas

Meningiomas represent the most common type of benign tumor of the extra-axial compartment. Although most meningiomas are benign World Health Organization (WHO) grade 1 lesions, the increasingly prevalent of WHO grade 2 lesion and occasional grade 3 lesions show worsened recurrence rates and morbidity. Multiple medical treatments have been evaluated but show limited efficacy. We review the status of medical management in meningiomas, highlighting successes and failures of various treatment options. We also explore newer studies evaluating the use of immunotherapy in management.

The Role of Immunotherapy in the Treatment of Rare Central Nervous System Tumors

Establishing novel therapies for rare central nervous system (CNS) tumors is arduous due to challenges in conducting clinical trials in rare tumors. Immunotherapy treatment has been a rapidly developing field and has demonstrated improvements in outcomes for multiple types of solid malignancies. In rare CNS tumors, the role of immunotherapy is being explored. In this article, we review the preclinical and clinical data of various immunotherapy modalities in select rare CNS tumors, including atypical meningioma, aggressive pituitary adenoma, pituitary carcinoma, ependymoma, embryonal tumor, atypical teratoid/rhabdoid tumor, and meningeal solitary fibrous tumor. Among these tumor types, some studies have shown promise; however, ongoing clinical trials will be critical for defining and optimizing the role of immunotherapy for these patients.

The Current Landscape of Immune Checkpoint Inhibitor Immunotherapy for Primary and Metastatic Brain Tumors

Antibodies against immune checkpoint inhibitors (ICIs) have revolutionized the treatment of multiple aggressive malignancies, including melanoma and non-small cell lung cancer. ICIs for the treatment of primary and metastatic brain tumors have been used with varying degrees of success. Here, we discuss the available evidence for the use of ICIs in the treatment of primary and metastatic brain tumors, highlighting challenges and opportunities for furthering this type of cancer immunotherapy in neuro-oncology.

The Tumor Immune Microenvironment in Primary CNS Neoplasms: A Review of Current Knowledge and Therapeutic Approaches

Primary CNS neoplasms are responsible for considerable mortality and morbidity, and many therapies directed at primary brain tumors have proven unsuccessful despite their success in preclinical studies. Recently, the tumor immune microenvironment has emerged as a critical aspect of primary CNS neoplasms that may affect their malignancy, prognosis, and response to therapy across patients and tumor grades. This review covers the tumor microenvironment of various primary CNS neoplasms, with a focus on glioblastoma and meningioma. Additionally, current therapeutic strategies based on elements of the tumor microenvironment, including checkpoint inhibitor therapy and immunotherapeutic vaccines, are discussed.

Immunotherapy for Meningiomas

Systemic treatment approaches are urgently needed for a subset of meningioma patients who do not achieve local tumor control with surgery and radiotherapy. Classical chemotherapy or anti-angiogenic agents exert only very limited activity in these tumors. Long-term survival of patients with advanced metastatic cancer following treatment with immune checkpoint inhibitors, i.e., monoclonal antibodies designed to unleash suppressed anticancer immune responses, has fostered hopes for benefit from similar approaches in patients with meningiomas that recur after standard local therapy. Moreover, a plethora of immunotherapy approaches beyond these drugs have entered clinical development or clinical practice for other cancer entities, including (i) novel immune checkpoint inhibitors that may act independently of T cell activity, (ii) cancer peptide or dendritic cell vaccines to induce anticancer immunity utilizing cancer-associated antigens, (iii) cellular therapies utilizing genetically modified peripheral blood cells to directly target cancer cells, (iv) T cell engaging recombinant proteins that link tumor antigen-binding sites to effector cell activating or recognition domains, or to immunogenic cytokines, and (v) oncolytic virotherapy utilizing attenuated viral vectors designed to specifically infect cancer cells, seeking to elicit systemic anticancer immunity. This chapter provides an overview of the principles of immunotherapy, summarizes ongoing immunotherapy clinical trials in meningioma patients, and discusses the applicability of established and emerging immunotherapy concepts to meningioma patients.

Immune Profiling of Meningiomas

Though meningiomas are generally regarded as benign tumors, there is increasing awareness of a large group of meningiomas that are biologically aggressive and refractory to the current standards of care treatment modalities. Coinciding with this has been increasing recognition of the important that the immune system plays in mediating tumor growth and response to therapy. To address this point, immunotherapy has been leveraged for several other cancers such as lung, melanoma, and recently glioblastoma in the context of clinical trials. However, first deciphering the immune composition of meningiomas is essential in order to determine the feasibility of similar therapies for these tumors. Here in this chapter, we review recent updates on characterizing the immune microenvironment of meningiomas and identify potential immunological targets that hold promise for future immunotherapy trials.

Emerging systemic treatment options in meningioma

PURPOSE

Meningiomas are the most frequently diagnosed intracranial neoplasms. Usually, they are treated by surgical resection in curative intent. Radiotherapy and stereotactic radiosurgery are commonly applied in the adjuvant setting in newly diagnosed atypical (CNS WHO grade 2), and anaplastic (CNS WHO grade 3) meningioma, especially if gross total resection is not feasible, and in recurrent cases. Conversely, the evidence for pharmacotherapy in meningioma is scarce.

METHODS

The available literature of systemic treatment in meningioma was screened using PubMed, and ongoing clinical trials were explored using ClinicalTrials.gov.

RESULTS

Classical cytotoxic agents, somatostatin analogs, and antihormone treatments have shown only limited efficacy. In contrast, tyrosine kinase inhibitors and monoclonal antibodies, especially those targeting angiogenic signaling such as sunitinib and bevacizumab, have shown promising antitumoral activity in small phase 2 trials. Moreover, results of recent landmark studies on (epi-)genetic alterations in meningioma revealed potential therapeutic targets which are currently under investigation. These include inhibitors of mammalian target of rapamycin (mTOR), focal adhesion kinase (FAK), cyclin-dependent kinases (CDK), phosphoinositide-3-kinase (PI3K), sonic hedgehog signaling, and histone deacetylases. In addition, clinical trials evaluating immune checkpoint inhibitors such as ipilimumab, nivolumab, pembrolizumab and avelumab are currently being conducted and early results suggest clinically meaningful responses in a subset of patients.

CONCLUSIONS

There is a paucity of high-level evidence on systemic treatment options in meningioma. However, interesting novel treatment targets have been identified in the last decade. Positive signals of anti-angiogenic agents, genomically targeted agents and immunotherapy in early phase trials should be confirmed in large prospective controlled trials.

Programmed death ligand 1 and tumor-infiltrating CD8+ T lymphocytes are associated with the clinical features in meningioma

Objective

To investigate the expression of programmed death ligand-1 (PD-L1) and the levels of CD8+ tumor-infiltrating lymphocytes (TILs) in meningioma as well as determine the association between their levels and the clinical outcomes.

Methods

We performed a retrospective case-control study on 93 patients with meningioma. The patients showed tumor recurrence and were matched with the control patients without recurrence in their age, gender, admission time, tumor sites, tumor volume, peritumoral brain edema (PTBE), Simpson grade resection, WHO grade, postoperative radiotherapy, and the follow-up duration. We reviewed the clinical data of patients and performed immunohistochemistry analysis to investigate the PD-L1 expression and the levels of CD8+ TILs. Multivariate logistic regression was performed to analyze the association between clinical features and immune markers. The conditional logistic regression models were used to calculate the odds ratios (ORs) with 95% confidence intervals (CIs), and Kaplan–Meier analysis was performed to analyze tumor recurrence.

Results

Tumor volume was correlated with the PD-L1 expression (P = 0.003, HR = 5.288, 95%CI, 1.786–15.651). PTBE served as an independent predictor of CD8+ TIL levels (P = 0.001, HR = 0.176, 95%CI 0.065–0.477). The levels of CD8+ TILs were associated with tumor recurrence (P = 0.020, OR = 0.325, 95%CI, 0.125–0.840).

Conclusion

Tumor volume was associated with PD-L1 expression, and PTBE was an independent predictor of CD8+ TIL levels in meningioma. CD8+ TIL levels correlated with tumor recurrence in meningioma.

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.

Advances in Molecular Biological and Translational Studies in World Health Organization Grades 2 and 3 Meningiomas: A Literature Review

The treatment of World Health Organization (WHO) grades 2 and 3 meningiomas remains difficult and controversial. The pathogenesis of high-grade meningiomas was expected to be elucidated to improve treatment strategies. The molecular biology of meningiomas has been clarified in recent years. High-grade meningiomas have been linked to NF2 mutations and 22q deletion. CDKN2A/B homozygous deletion and TERT promoter mutations are independent prognostic factors for WHO grade 3 meningiomas. In addition to 22q loss, 1p, 14p, and 9q loss have been linked to high-grade meningiomas. Meningiomas enriched in copy number alterations may be biologically invasive. Furthermore, several new comprehensive classifications of meningiomas have been proposed based on these molecular biological features, including DNA methylation status. The new classifications may have implications for treatment strategies for refractory aggressive meningiomas because they provide a more accurate prognosis compared to the conventional WHO classification. Although several systemic therapies, including molecular targeted therapies, may be effective in treating refractory aggressive meningiomas, these drugs are being tested. Systemic drug therapy for meningioma is expected to be developed in the future. Thus, this review aims to discuss the distinct genomic alterations observed in WHO grade 2 and 3 meningiomas, as well as their diagnostic and therapeutic implications and systemic drug therapies for high-grade meningiomas.

Synthesizing Molecular and Immune Characteristics to Move Beyond WHO Grade in Meningiomas: A Focused Review

No portion of this manuscript has previously been presented. Meningiomas, the most common primary intracranial tumors, are histologically categorized by the World Health Organization (WHO) grading system. While higher WHO grade is generally associated with poor clinical outcomes, a significant subset of grade I tumors recur or progress, indicating a need for more reliable models of meningioma behavior. Several groups have developed risk scores based on molecular or immunologic characteristics. These classification schemes show promise, with several models preliminarily demonstrating similar or superior accuracy to WHO grading. Improved understanding of immune system recognition and targeting of meningioma subtypes is necessary to advance the predictive power, as well as develop new therapies. Here, we characterize meningioma molecular drivers, predictive of recurrence and progression, and describe specific aspects of the immune response to meningiomas while highlighting critical questions and ongoing research. Relevant manuscripts of interest were identified using a systematic approach and synthesized into this focused review. Finally, we summarize the ongoing and completed clinical trials for immunotherapy in meningiomas and offer perspective on future directions.

Immune checkpoint inhibitor therapy for recurrent meningiomas: a retrospective chart review

INTRODUCTION

Meningiomas that progress despite surgery and radiotherapy represent an unmet medical need. Expression of PD-1 and PDL-1 has been demonstrated in meningiomas and is proportional to tumor grade, suggesting a potential role for anti-PD-1/anti-PDL-1 inhibitor therapy. We explored the potential role of immunotherapy for recurrent meningiomas by describing progression-free survival (PFS) and overall survival (OS) in a single-center patient sample.

METHODS

This is a retrospective chart review of patients with meningioma who were treated with PD-1 inhibitors at UPMC Hillman Cancer Center. Any patient over age 18 who received immunotherapy was included in this study. Patients received treatment until development of disease progression, intolerable toxicities or adverse events, death, or oncologist decision. Serial radiographic assessments were made every 3-6 months.

RESULTS

Between January 2015 and November 2021, eight patients received anti-PD-1 therapy. All patients underwent tumor resection and radiosurgery, and four patients received prior systemic therapy. Six out of eight patients experienced symptomatic perilesional edema and three patients experienced exacerbation of seizures. Median PFS was 7 months (95% CI 1-24) and median OS was 1.75 years (95% CI 1.5-4.0). In patients with positive PD-1/PD-L1 expression, median PFS was 2 years and median OS was 3 years.

CONCLUSION

Anti-PD-1 therapy was associated with a manageable safety profile in patients with recurrent meningiomas. Patients with WHO Grade III tumors and positive PD-1/PD-L1 expression were noted to have increased PFS and OS, suggesting a potential role for immunotherapy in these patients, but further studies are needed to investigate this in a larger patient population.

m6A Regulator Expression Segregates Meningiomas Into Biologically Distinct Subtypes

BACKGROUND

Meningiomas are the most common primary intracranial tumors in adults. According to the 2021 World Health Organization (WHO) classification of central nervous system tumors, approximately 80% of meningiomas are WHO grade 1, that is, histopathologically benign, whereas about 20% are WHO grade 2 or grade 3, showing signs of atypia or malignancy. The dysregulation of N6-methylation (m⁶A) regulators is associated with disorders of diverse critical biological processes in human cancer. This study aimed to explore whether m⁶A regulator expression was associated with meningioma molecular subtypes and immune infiltration.

METHODS

We evaluated the m⁶A modification patterns of 160 meningioma samples based on 19 m⁶A regulators and correlated them with immune infiltration characteristics. Novel molecular subtypes were defined based on prognostic hub gene expression.

RESULTS

Two meningioma clusters were identified based on the expression of 19 m⁶A regulators. In cluster 1, 607 differentially expressed genes (DEGs) were upregulated and 519 were downregulated. A total of 1,126 DEGs comprised three gene expression modules characterized by turquoise, blue, and gray. Functional annotation suggested that the turquoise module was involved in Wnt-related and other important cancer-related pathways. We identified 32 hub genes in this module by constructing a protein-protein interaction network. The meningioma samples were divided into two molecular subtypes. EPN1, EXOSC4, H2AX, and MZT2B not only showed significant differences between meningioma molecular subtypes but also had the potential to be the marker genes of specific meningioma subtypes.

CONCLUSION

m⁶A regulator gene expression may be a novel prognostic marker in meningioma.

Chemotherapy and targeted therapies for meningiomas: what is the evidence?

PURPOSE OF REVIEW

Although most meningiomas are slow growing tumors mainly controlled by surgery with or without radiotherapy, aggressive meningiomas that fail these conventional treatments constitute a rare situation, a therapeutic challenge and an unmet need in neuro-oncology.

RECENT FINDING

Mutational landscape in recurrent high-grade meningiomas includes mainly NF2 mutation or 22q chromosomal deletion, whereas telomerase reverse transcriptase promoter, BAP-1 and CDK2NA mutations were also found in aggressive meningiomas. Pi3K-Akt-mTOR pathway is currently the most relevant intracellular signaling pathway target in meningiomas with preliminary clinical activity observed. Assessment of drug activity with progression free survival rate at 6 months is challenging in regard to meningioma growth rate heterogeneity, so that 3-dimensional growth rate before and during treatment could be considered in the future to selected new active drugs.

SUMMARY

Despite a low evidence level, some systemic therapies may be considered for patients with recurrent meningioma not amenable to further surgery or radiotherapy. In recurrent high-grade meningioma, everolimus-octreotide combination, bevacizumab, sunitinib and peptide receptor radionuclide therapy exhibit a signal of activity that may justify their clinical use. Despite a lack of clear signal of activity to date, immunotherapy may offer new perspectives in the treatment of these refractory tumors.

The role of systemic inflammatory cells in meningiomas

The aim of this review is to describe the inflammatory systemic cell infiltrate and its role in pathophysiology and prognostic implications of meningiomas. Articles from PubMed describing inflammation and immune cells in meningioma were systematically selected and reviewed. Infiltrating inflammatory cells are common in meningiomas and correlate with tumor behavior and peritumoral edema. The immune cell infiltrate mainly comprised macrophages, CD4 + T cells of the Th1 and Th2 subtype, CD8 + cytotoxic T cells, mast cells, and to a lesser degree B cells. The polarization of macrophages to M1 or M2 states, as well as the differentiation of T-helper cells to Th1 or Th2 subsets, is of prognostic value, but whether or not the presence of macrophages is associated with the degree of malignancy of the tumor is controversial. The best documented immunosuppressive and tumor-promoting mechanism is the expression of programmed cell death protein 1 (PD-1/PD-1L) which is found on both tumor cells and tumor-infiltrating immune cells. The immune cell infiltration varies between different meningiomas. It contributes to a microenvironment with potential contradictory effects on tumor growth and edema. The immune mechanisms are potential therapeutic targets provided that their effects can be comprehensively understood.

Meningioma-Brain Crosstalk: A Scoping Review

Background: In recent years, it has become evident that the tumoral microenvironment (TME) plays a key role in the pathogenesis of various cancers. In meningiomas, however, the TME is poorly understood, and it is unknown if glia cells contribute to meningioma growth and behaviour. Objective: This scoping review investigates if the literature describes and substantiates tumour-brain crosstalk in meningiomas and summarises the current evidence regarding the role of the brain parenchyma in the pathogenesis of meningiomas. Methods: We identified studies through the electronic database PubMed. Articles describing glia cells and cytokines/chemokines in meningiomas were selected and reviewed. Results: Monocytes were detected as the most abundant infiltrating immune cells in meningiomas. Only brain-invasive meningiomas elicited a monocytic response at the tumour-brain interface. The expression of cytokines/chemokines in meningiomas has been studied to some extent, and some of them form autocrine loops in the tumour cells. Paracrine interactions between tumour cells and glia cells have not been explored. Conclusion: It is unknown to what extent meningiomas elicit an immune response in the brain parenchyma. We speculate that tumour-brain crosstalk might only be relevant in cases of invasive meningiomas that disrupt the pial-glial basement membrane.

Long-Term Non-progression in Metastatic Breast Cancer Beyond 5 Years: Case Series and Review

Purpose of review

Metastatic breast cancer (MBC) was traditionally viewed as homogeneously progressive and incurable among all comers, but there is new evidence that MBC harbors a range of tumor molecular/immune subtypes and degrees of aggressiveness. Thus, MBC is not rapidly fatal in all affected patients.

Recent findings

A small subset of patients will attain long-term disease control, or undetectable disease, and will enjoy a prolonged survival with little disability from their disease or treatment. Though the term is controversial, some patients with long-term non-detectable disease may effectively be considered “cured”. To best advise treatment options in these patients, it is imperative to identify patients most likely to benefit from aggressive treatment.

Summary

In this review, we delineate the clinical, pathologic, and disease characteristics associated with long-term non-progression in MBC. We include a single institution case series of long-term non-progressive MBC patients and their characteristics as an example of the frequency of this sub-population of MBC. Future prospective trials are warranted to examine the utility of clinical characteristics as predictors of long-term survival in MBC.

Rare Diseases of the Oral Cavity, Neck, and Pharynx

Diseases occurring with an incidence of less than 1-10 cases per 10 000 individuals are considered as rare. Currently, between 5 000 and 8 000 rare or orphan diseases are known, every year about 250 rare diseases are newly described. Many of those pathologies concern the head and neck area. In many cases, a long time is required to diagnose an orphan disease. The lives of patients who are affected by those diseases are often determined by medical consultations and inpatient stays. Most orphan diseases are of genetic origin and cannot be cured despite medical progress. However, during the last years, the perception of and the knowledge about rare diseases has increased also due to the fact that publicly available databases have been created and self-help groups have been established which foster the autonomy of affected people. Only recently, innovative technical progress in the field of biogenetics allows individually characterizing the genetic origin of rare diseases in single patients. Based on this, it should be possible in the near future to elaborate tailored treatment concepts for patients suffering from rare diseases in the sense of translational and personalized medicine. This article deals with orphan diseases of the lip, oral cavity, pharynx, and cervical soft tissues depicting these developments. The readers will be provided with a compact overview about selected diseases of these anatomical regions. References to further information for medical staff and affected patients support deeper knowledge and lead to the current state of knowledge in this highly dynamic field.

Review of Atypical and Anaplastic Meningiomas: Classification, Molecular Biology, and Management

Although the majority of meningiomas are slow-growing and benign, atypical and anaplastic meningiomas behave aggressively with a penchant for recurrence. Standard of care includes surgical resection followed by adjuvant radiation in anaplastic and partially resected atypical meningiomas; however, the role of adjuvant radiation for incompletely resected atypical meningiomas remains debated. Despite maximum treatment, atypical, and anaplastic meningiomas have a strong proclivity for recurrence. Accumulating mutations over time, recurrent tumors behave more aggressively and often become refractory or no longer amenable to further surgical resection or radiation. Chemotherapy and other medical therapies are available as salvage treatment once standard options are exhausted; however, efficacy of these agents remains limited. This review discusses the risk factors, classification, and molecular biology of meningiomas as well as the current management strategies, novel therapeutic approaches, and future directions for managing atypical and anaplastic meningiomas.

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.

NF2 mutation status and tumor mutational burden correlate with immune cell infiltration in meningiomas

BACKGROUND

The tumor microenvironment is an emerging biomarker of underlying genomic heterogeneity and response to immunotherapy-based treatment regimens in solid malignancies. How tumor mutational burden influences the density, distribution, and presence of a localized immune response in meningiomas is unknown.

METHODS

Representative hematoxylin and eosin slides were reviewed at 40X to assess for the density of inflammatory cells. Lymphocytes and macrophages were quantified in the following ordinal manner: 0 = not present, 1 = 1-25 cells present, and 2 = greater than 26 cells present. Immune cell infiltrate grade was scored for both scattered and aggregated distributions. Next generation targeted sequencing was performed on all meningiomas included in this study.

RESULTS

One hundred and forty-five meningiomas were evaluated in this study. Lymphocytes were observed in both scattered (95.9%) and aggregated (21.4%) distributions. A total of 115 (79.3%) meningiomas had 1-25 scattered lymphocytes, and 24 (16.6%) had > 25 scattered lymphocytes, and 6 (4.1%) had no scattered lymphocytes. Twenty (13.8%) meningiomas had 1-25 aggregated lymphocytes. Eleven (7.6%) had > 25 aggregated lymphocytes and 114 (78.6%) had no aggregated lymphocytes. Six (4.1%) meningiomas had 1-25 aggregated macrophages, 5 (3.4%) had > 25 aggregated macrophages, and 134 (92.4%) had no aggregated macrophages. Density of aggregated lymphocytes and aggregated macrophages were associated with higher tumor grade, P = 0.0071 and P = 0.0068, respectively. Scattered lymphocyte density was not associated with meningioma grade. The presence of scattered lymphocytes was associated with increased tumor mutational burden. Meningiomas that did not have scattered lymphocytes had a mean number of single mutations of 2.3 ± 2.9, compared with meningiomas that had scattered lymphocytes, 6.9 ± 20.3, P = 0.03. NF2 mutations were identified in 59 (40.7%) meningiomas and were associated with increased density of scattered lymphocytes. NF2 mutations were seen in 0 (0%) meningiomas that did not have scattered lymphocytes, 46 (40.0%) meningiomas that had 1-25 scattered lymphocytes, and 13 (54.2%) meningiomas that had > 25 scattered lymphocytes, P = 0.046.

CONCLUSIONS

Our findings suggest that distribution of immune cell infiltration in meningiomas is associated with tumor mutational burden. NF2 mutational status was associated with an increasing density of scattered lymphocytes. As the role of immunotherapy in meningiomas continues to be elucidated with clinical trials that are currently underway, these results may serve as a novel biomarker of tumor mutational burden in meningiomas.

A Rapid Robust Method for Subgrouping Non-NF2 Meningiomas According to Genotype and Detection of Lower Levels of M2 Macrophages in AKT1 E17K Mutated Tumours

The majority of meningiomas are grade I, but some grade I tumours are clinically more aggressive. Recent advances in the genetic study of meningiomas has allowed investigation into the influence of genetics on the tumour microenvironment, which is important for tumorigenesis. We have established that the endpoint genotyping method Kompetitive Allele Specific PCR (KASP™) is a fast, reliable method for the screening of meningioma samples into different non-NF2 mutational groups using a standard real-time PCR instrument. This genotyping method and four-colour flow cytometry has enabled us to assess the variability in the largest immune cell infiltrate population, M2 macrophages (CD45+HLA-DR+CD14+CD163+) in 42 meningioma samples, and to suggest that underlying genetics is relevant. Further immunohistochemistry analysis comparing AKT1 E17K mutants to WHO grade I NF2-negative samples showed significantly lower levels of CD163-positive activated M2 macrophages in meningiomas with mutated AKT1 E17K, signifying a more immunosuppressive tumour microenvironment in NF2 meningiomas. Our data suggested that underlying tumour genetics play a part in the development of the immune composition of the tumour microenvironment. Stratifying meningiomas by mutational status and correlating this with their cellular composition will aid in the development of new immunotherapies for patients.

Possible Abscopal Effect Observed in Frontal Meningioma After Localized IMRT on Posterior Meningioma Resection Cavity Without Adjuvant Immunotherapy

Background: Localized radiation therapy (RT) is known to infrequently cause off-target or “abscopal” effects at distant metastatic lesions. The mechanism through which abscopal effects occur remains unknown, but is thought to be caused by a humoral immune response to tumor-specific antigens generated by RT. Combination treatment regimens involving RT and immunotherapy to boost the humoral immune response have demonstrated synergistic effects in promoting and accelerating abscopal effects in metastatic cancer. Nevertheless, abscopal effects, particularly after RT alone, remain exceedingly rare.

Case Presentation: We report the case of an 84-year-old man with an atypical meningioma, who demonstrated a radiographically significant response to an untreated second intracranial lesion, likely also a meningioma, after intensity-modulated radiation therapy (IMRT) to a separate, detatched resection cavity. Serial annual MRI imaging starting at 2- to 3.5-year (most recent) post-IMRT follow-up demonstrated a persistent decrease in both tumor size and surrounding edema in the untreated second lesion, suggestive of a possible abscopal effect.

Conclusions: We describe here the first report of a potential abscopal effect in meningioma, summarize the limited literature on the topic of abscopal effects in cancer, and detail the existing hypothesis on how this phenomenon may occur and possibly relate to the development of future treatments for patients with metastatic disease.