Medical Management of Meningiomas: Current Status, Failed Treatments, and Promising Horizons

Impact on natural history of atypical meningioma after changes in 2016 edition of the world health organization (WHO) classification of central nervous system tumors: a literature review

Meningiomas and their WHO histological diagnostic criteria is complex, especially for grade 2 tumors presenting a interobserver discordance as high as 12.2%. The 2016 edition of the WHO Classification of CNS tumors recommended brain invasion as a stand-alone grading criterion for diagnosing an atypical grade 2 meningioma (AM). To provide an overview of the classification of 2016 WHO impact on the natural history of atypical meningioma (AM) relative to previous classification. To achieve this goal, we selected articles from the period 2017-2024 in Medline search on atypical meningiomas and analyzed them after following the following criteria: 1) reports with confirmed histopathological diagnosis according to WHO 2016 and or 2021 criteria; 2) series and case reports; 3) detailed and individualized clinical outcomes for AM; and 4) papers written in English; after that a total of 3445 patients reported in 67 manuscripts from worldwide centers from 2017 to March 2024 were analyzed. The patient's age at the time of surgery ranged from 1 month to 97 years (mean 52.28 ± 18.7 years). The most common tumor site was the convexity, accounting for 67.8%, followed by the skull base in 30.6%, ventricle in 1%, and spine in 0.6%; Gross total resection (GTR) was performed in 71.25% and subtotal resection (STR) in 28.75%; 1021 patients (29.63%) underwent adjuvant radiotherapy, and 22 patients (0.6%) were treated with adjuvant chemotherapy; tumor recurrence was reported in 1221 patients (35.44%) and 859 deaths (24.93%). 1) AM prevalence in females; 2) AM age distribution similar to the distribution of meningiomas in general; 3) AM recurrence rate of 35.44%, despite the high rate of GTR, which was higher than previously reported; 4) deepening knowledge in molecular mechanism of tumor progression will provide alternative therapeutic approaches for AM.

Drug target therapy and emerging clinical relevance of exosomes in meningeal tumors

Meningioma is the most common central nervous system (CNS) tumor. In recent decades, several efforts have been made to eradicate this disease. Surgery and radiotherapy remain the standard treatment options for these tumors. Drug therapy comes to play its role when both surgery and radiotherapy fail to treat the tumor. This mostly happens when the tumors are close to vital brain structures and are nonbenign. Although a wide variety of chemotherapeutic drugs and molecular targeted drugs such as tyrosine kinase inhibitors, alkylating agents, endocrine drugs, interferon, and targeted molecular pathway inhibitors have been studied, the roles of numerous drugs remain unexplored. Recent interest is growing toward studying and engineering exosomes for the treatment of different types of cancer including meningioma. The latest studies have shown the involvement of exosomes in the theragnostic of various cancers such as the lung and pancreas in the form of biomarkers, drug delivery vehicles, and vaccines. Proper attention to this new emerging technology can be a boon in finding the consistent treatment of meningioma.

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.

A Comprehensive View(COUP D'OEIL) of Brain Tumors from Eastern India

BACKGROUND

Brain tumors have always fascinated and intrigued histopathologists due to their diverse morphology and rarity. Recent surge in the molecular developments has further posed a challenge in diagnosis especially in a resource limited setting. Therefore, comprehensive tumor registries have become quintessential to compare our existing database with new found knowledge.

METHODS

A descriptive retrospective study was carried out on archival data of 5 years in a neuroscience institute. All neurosurgical cases operated with complete clinical history and definitive histopathological diagnosis were included. The cases were analyzed with reference to age, sex, location of the lesion, grade of the tumor, and immunohistochemical profile as available and compared with existing registries and literature.

RESULTS

The primary brain tumors accounted for 38.29% of all pathologies. Majority of cases clustered around 40-70 years of age (65%). Pediatric (0-19 years) cases comprised 7%. Most common primary brain tumor found in the adult population was meningioma (28%) followed by Glioblastoma (25%). The most common neoplasm in pediatric age group were gliomas (46.29%) followed by embryonal neoplasms. Pituitary adenomas (PAs) constituted 16% of all intracranial neoplasm. Gonadotroph adenoma was the most common of the nonfunctional adenomas constituting one half of the PAs (51.72%). Somatotroph adenoma was most common in the functional group constituting 20% of all PAs.

CONCLUSIONS

The layout of cases when compared with available brain tumor registries showed nearly similar trends in distribution. Our study succored data from the population in eastern part of India of which our institute is a major referral centre for neurosurgical cases.

The Role of Pharmacotherapy in Treatment of Meningioma: A Systematic Review

The safety and efficacy of various pharmacotherapeutic regimens on refractory meningiomas have been the focus of investigations. We present a comprehensive review of the previous efforts and the current state of ongoing clinical trials. A PRISMA-compliant review of the MEDLINE and ClinicalTrial.gov databases of the National Library of Medicine were performed. The primary outcomes of interest for included articles were radiographic response, overall survival, progression-free survival, six-month progression-free survival, and adverse events. Overall, 34 completed trials and 27 ongoing clinical trials were eligible. Six-month progression-free survival was reported in 6-100% of patients in the completed studies. Hematological disorders were the most common adverse events. Of the ongoing clinical trials identified, nine studies are phase I clinical trials, eleven are phase II trials, two are phase I and II trials, one is phase II and III, and two trials do not have a designated phase. Currently, there is no effective chemotherapy for refractory or recurrent meningiomas. Several promising targeted agents have been developed and are currently being investigated in the hope of identifying novel therapeutic strategies for the treatment of this pathology.

Advances in Central Nervous System Tumor Classification

Historically, the classification of tumors of the central nervous system (CNS) relies on the histologic appearance of cells under a microscope; however, the molecular era of medicine has resulted in new diagnostic paradigms anchored in the intrinsic biology of disease. The 2021 World Health Organization (WHO) reformulated the classification of CNS tumors to incorporate molecular parameters, in addition to histology, to define many tumor types. A contemporary classification system with integrated molecular features aims to provide an unbiased tool to define tumor subtype, the risk of tumor progression, and even the response to certain therapeutic agents. Meningiomas are heterogeneous tumors as depicted by the current 15 distinct variants defined by histology in the 2021 WHO classification, which also incorporated the first moelcular critiera for meningioma grading: homozygous loss of CDKN2A/B and TERT promoter mutation as criteria for a WHO grade 3 meningioma. The proper classification and clinical management of meningioma patients requires a multidisciplinary approach, which in addition to the information on microscopic (histology) and macroscopic (Simpson grade and imaging), should also include molecular alterations. In this chapter, we present the most up-to-date knowledge in CNS tumor classification, particularly in meningioma, in the molecular era and how it could affect their future classification and clinical management of patients with these diseases.

Case report: Clinical report of co-occurrence of pituitary adenoma and meningioma in the sellar region after meningioma treatment

The coexistence of meningioma and pituitary adenoma is very rare, especially in the same location after meningioma surgery. Here, we reported a case of coexisting meningioma and pituitary adenoma secondary to postoperative meningioma in the sellar region in a patient who had not received radiation therapy before the second surgery. A 61-year-old woman underwent craniotomy for tumor resection for sellar meningioma in 2017, and postoperative imaging showed no residual in the surgical area. In 2022, the patient had a history of decreased vision again. MRI showed the possibility of postoperative pituitary adenoma in the sellar region. The patient underwent endoscopic resection of the skull base lesion again. After surgery, the patient's visual symptoms improved. Histology of the sellar tumor showed both meningioma (meningeal epithelial type and WHO grade I) and pituitary adenoma in the same section. The coexistence of meningioma and pituitary adenoma is a very rare surgical entity. This report provides a theoretical basis for the selection of intracerebral tumor surgery and provides a diagnostic basis and treatment reference for patients diagnosed with meningioma and pituitary adenoma at the same time.

Bone Invasive Meningioma: Recent Advances and Therapeutic Perspectives

Meningioma is the most common primary neoplasm of the central nervous system (CNS). Generally, these tumors are benign and have a good prognosis. However, treatment can be challenging in cases with aggressive variants and poor prognoses. Among various prognostic factors that have been clinically investigated, bone invasion remains controversial owing to a limited number of assessments. Recent study reported that bone invasion was not associated with WHO grades, progression, or recurrence. Whereas, patients with longer-recurrence tended to have a higher incidence of bone invasion. Furthermore, bone invasion may be a primary preoperative predictor of the extent of surgical resection. Increasing such evidence highlights the potential of translational studies to understand bone invasion as a prognostic factor of meningiomas. Therefore, this mini-review summarizes recent advances in pathophysiology and diagnostic modalities and discusses future research directions and therapeutic strategies for meningiomas with bone invasion.

Preoperative hematological inflammatory markers associated with grade and survival in Meningiomas

Meningiomas represent the most frequently diagnosed intracranial tumors. Inflammatory cells present in the tumor can modulate both antitumor and protumor functions, and modify the therapeutic response. Hematological inflammatory parameters have provided prognostic information useful in the treatment and clinical evaluation of several tumors. The aim of this study was to evaluate preoperative hematological markers of patients with meningiomas and to relate them to clinical variables and recurrence-regrowth free survival. Eighty-nine patients without corticosteroid therapy were included. Blood test results and tumor characteristics were collected from medical records. Associations between clinical characteristics and the recurrence-regrowth free survival (RFS) were evaluated using Cox proportional hazard analysis and Kaplan-Meier curves. The receiver operating characteristic (ROC) curves were constructed. Of the 89 cases, 73 (82%) were grade I and 16 (18%) grade II. The mean age was 53 ± 13.9 years, with higher frequency in women. Anemia was observed in 23.6% and neutrophilia in 42% of the patients. In univariate analysis, anemia (p = 0.04), neutrophilia (p = 0.02) and neutrophil/lymphocyt ratio (NLR) (p = 0.02) were associated with an increased risk of recurrence-regrowth and shorter RFS. In multivariate analysis, anemia and NLR > 4.1 represented a higher risk of recurrence-regrowth (p = 0.003). The ROC curve analysis showed that only the lymphocyte/monocyte (L/M) > 2.5 was able to predict the tumor grade. The preoperative presence of anemia, neutrophilia, NLR > 4.1 and L/M > 2.5 were associated with a worse prognosis in meningiomas. The use of preoperative hematological inflammatory parameters as prognostic factors can be promissing for evaluation and follow-up of meningiomas.

Biological Treatments of Neurofibromatosis Type 2 and Other Skull Base Disorders

Studies of genomic alterations that occur in skull base tumors have provided information regarding biological aberrations that are necessary for the growth and maintenance of these tumors. This has led to the development and initiation of clinical trials incorporating biological treatments for many skull base tumors. The exciting developments of molecularly targeted therapy for the treatment of skull base tumors may provide noninvasive therapeutic options for patients that can be used either alone or in combination with surgery and/or radiation therapy. Future analysis and continued scientific discovery of treatments for skull base tumors can lead to improved outcomes in patients.

Differences in the expression of SSTR1-5 in meningiomas and its therapeutic potential

Beyond microsurgical resection and radiation therapy, there are currently no established treatment alternatives for meningioma patients. In selected cases, peptide radio receptor therapy (PRRT) can be implemented. For this purpose, a radionuclide is bound to a substance targeting specific receptors in meningiomas. One of them is somatostatin receptor 2, which can be found in most meningiomas. However, other somatostatin receptors (SSTR) exist, but their expressions have only been described in small case series. In this study, we analyzed the expression of SSTR1, 2A, 3, 4, and 5 in a large cohort of meningiomas in order to enable further refinement of this innovative treatment option. Overall, 726 tumor samples were processed into tissue microarrays and stained for SSTR1, 2A, 3, 4, and 5 immunohistochemically. Microscopic evaluation was done with an established semiquantitative score regarding percentual quantification and staining intensity, and results were correlated with clinical data. There was a significant lower rate of SSTR1 expression in meningiomas of male patients. Older age was associated with higher expression of SSTR1, 2A, and 5 and lower scores for SSTR3 and 4. Tumors treated with radiotherapy before resection showed lower rates of SSTR1 and 5 expression, while recurrent meningiomas had lower SSTR1 scores. Tumor tissue from patients suffering from neurofibromatosis type 2 had lower expression scores for SSTR1, 2, and 5. For SSTR3 and 4, NF2 patients showed higher scores than sporadic tumors. Spinal meningiomas had higher scores for SSTR1, 4, and 5 compared tumor location of the skull base and convexity/falx. Overall, higher WHO grade was associated with lower SSTR scores. While all SSTRs were expressed, there are marked differences of SSTR expression between meningioma subgroups. This has the potential to drive the development of more selective PRRT substances with higher treatment efficacy.

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.

Primary and Secondary Optic Nerve Sheath Meningioma

Objective  This study was aimed to review issues relating to the recognition, radiographic diagnosis, monitoring, and management of primary and secondary optic nerve sheath meningioma (ONSM). Design  This study is a review of peer-reviewed literature combined with illustrative case studies. Participants and Methods  A literature search was conducted via the PubMed database using pertinent search terms. Selected articles were limited to those written or translated into English. Additional works cited within articles were also included. Individual cases were drawn from the experience of a tertiary academic neuroophthalmic and orbital practice. Tables summarize radiotherapeutic and surgical studies, excluding single case reports and studies focusing on meningioma of intracranial origin. Main Outcome Measurements  Review of reported surgical and radiotherapeutic series is the primary measurement. Results  The natural history of optic nerve sheath meningiomas is primarily characterized by progressive ipsilateral vision loss. Diagnosis is typically based on radiographic imaging findings, with biopsy remaining indicated in some patients. Management strategies may include observation, radiation, and/or surgical intervention, or a combination of these approaches. The role of surgery, especially with respect to primary ONSM (pONSM), remains controversial. Advancement of radiotherapy techniques has shifted modern treatment paradigms in pONSM toward radiation as primary treatment, as surgical outcomes are inferior in major studies. Although radiation remains the treatment of choice in many cases, selected patients may benefit from surgery, especially in the setting of secondary ONSM (sONSM). Conclusion  A wide variety of radiotherapeutic and surgical treatment modalities for ONSM exist. The specific indications for each management strategy continue to be redefined.

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.

Meningioma: A Review of Clinicopathological and Molecular Aspects

Meningiomas are the most the common primary brain tumors in adults, representing approximately a third of all intracranial neoplasms. They classically are found to be more common in females, with the exception of higher grades that have a predilection for males, and patients of older age. Meningiomas can also be seen as a spectrum of inherited syndromes such as neurofibromatosis 2 as well as ionizing radiation. In general, the 5-year survival for a WHO grade I meningioma exceeds 80%; however, survival is greatly reduced in anaplastic meningiomas. The standard of care for meningiomas in a surgically-accessible location is gross total resection. Radiation therapy is generally saved for atypical, anaplastic, recurrent, and surgically inaccessible benign meningiomas with a total dose of ~60 Gy. However, the method of radiation, regimen and timing is still evolving and is an area of active research with ongoing clinical trials. While there are currently no good adjuvant chemotherapeutic agents available, recent advances in the genomic and epigenomic landscape of meningiomas are being explored for potential targeted therapy.

WHO Grade I Meningioma Recurrence: Identifying High Risk Patients Using Histopathological Features and the MIB-1 Index

Objective: In this study, we identify clinical, radiographic, and histopathologic prognosticators of overall, early, and post-median recurrence in World Health Organization (WHO) grade I meningiomas. We also determine a clinically relevant cutoff for MIB-1 to identify patients at high risk for recurrence.

Method: A retrospective review of WHO grade I meningioma patients with available MIB-1 index data who underwent treatment at our institution from 2007 to 2017 was performed. Univariate and multivariate analyses, and recursive partitioning analysis (RPA), were used to identify risk factors for overall, early (within 24 months), and post-median (>24 months post-treatment) recurrence.

Result: A total of 239 patients were included. The mean age was 60.0 years, and 69.5% of patients were female. The average follow-up was 41.1 months. All patients received surgery and 2 patients each received either adjuvant radiotherapy (2/239) or gamma knife treatment (2/239). The incidence of recurrence was 10.9% (26/239 patients), with an average time to recurrence of 33.2 months (6–105 months). Posterior fossa tumor location (p = 0.004), MIB-1 staining (p = 0.008), nuclear atypia (p = 0.003), and STR (p < 0.001) were independently associated with an increased risk of recurrence on cox-regression analysis. RPA for overall recurrence highlighted extent of resection, and after gross total resection (GTR), a MIB-1 index cutoff of 4.5% as key prognostic factors for recurrence. Patients with a GTR and MIB-1 >4.5% had a similar incidence of recurrence as those with STR (18.8 vs. 18.6%). Variables independently associated with early recurrence on binary logistic regression modeling included STR (p = 0.002) and nuclear atypia (p = 0.019). RPA confirmed STR as associated with early recurrence.

Conclusion: STR, posterior fossa location, nuclear atypia, and elevated MIB-1 index are prognostic factors for WHO grade I meningioma recurrence. Moreover, MIB-1 index >4.5% is prognostic for recurrence in patients with GTR. Verification of our findings in larger, multi-institutional studies could enable risk stratification and recommendations for adjuvant radiotherapy following resection of WHO grade I meningiomas.

DNA repair and cell synthesis proteins: immunohistochemical expression and correlation with recurrence-regrowth in meningiomas

Meningiomas are considered the second most common neoplasm of the central nervous system in adults. Most of them are benign with slow growth, frequent in women and with a high recurrence rate. In tumors, DNA error repair processes lose efficacy, providing mutagenesis and genomic instability. This work evaluated the expression of proteins involved in cell synthesis (cyclin D1) and DNA errors repair (MUTYH, XPF, XPG) in meningiomas, relating them to clinical, tumor and survival variables. The study included 85 patients, with a mean age of 52 ± 13.3 years and most of them women (2:1 ratio). Sixty-seven cases were grade I (79%). Grade II tumors were independent predictors of recurrence-regrowth (HR: 2.8; p = 0.038). The high expression of cyclin D1 was associated with grade II (p = 0.001) and low MUTYH expression with grade I (p = 0.04). Strong expression of XPF and XPG was associated with grade II (p = 0.002; p < 0.001) and with recurrence-regrowth (p = 0.04; p = 0.003). Strong XPF expression was significantly related to large tumors (p = 0.03). An association of cyclin D1, MUTYH and XPF were found. Survival was not associated with the expression of any of the proteins studied. To know the role of DNA repair proteins and cell synthesis is important for understanding the processes of origin and tumor development. Grade II meningiomas and strong expression of XPF and XPG were predictors of recurrence or regrowth and may assist in clinical management, considering the high recurrence of meningiomas and the absence of consensus regarding treatment.

A Retrospective Interventional Cohort Study to Assess the Safety and Efficacy of Sandostatin LAR for Treatment of Recurrent and/or Refractory Meningiomas

Background: Meningiomas are the most common adult primary intracranial tumors in the United States. Despite high recurrence rate of atypical and malignant subtypes, there is no approved drug indicated specifically for meningioma. Since the majority of meningiomas exhibit high density of somatostatin receptors subtypes, somatostatin analogs have been under close investigation. The aim of this study was to evaluate efficacy and safety of Sandostatin LAR (octreotide) in patients with progressive, and/or recurrent meningioma, and identify subset of patients who were more likely to benefit from this treatment.

Methods: A total of 43 patients ≥ 18 years old were included in the retrospective chart review. The patients underwent treatment with Sandostatin LAR (octreotide) from 01.01.2010 to 06.01.2017 at the University of California, Irvine after confirmation of the diagnosis. Six months progression free survival (PFS6) was defined as a primary endpoint, and the overall survival (OS), safety, and toxicity were identified as secondary endpoints.

Results: The OS for 6 months, 1, and 3 years for all WHO grades was 94.8, 88.1, and 67.0%, respectively. The PFS6 for WHO I, II, III, and all was 89.4, 89, 33.3, and 80% respectively. For patients with no prior surgeries, chemotherapy or radiation, the PFS6 was 88.9, 84.8, and 94.8%, respectively. Interestingly, the PFS6 was 90.5% for skull-based and 80% for 3–6 cm tumors. Patients with tumors in parasagittal location had PFS6 of 83.3% compared to PFS6 of 50.0% for patients with convexity tumors. Evaluation of PFS6 based on the effect of estrogen and progesterone on meningioma identified that ER-PR+ tumors had PFS6 of 87.8% while patients with ER-PR- meningiomas had PFS6 of 62.5%. Median TTP for WHO grade I, II, and III was 3.1, 2.40, and 0.26 years, respectively. Subgroup analysis showed that median TTP was 3.1 years for <3 cm tumors, 3.22 years for skull-based tumors, 2.37 years for patients with prior surgeries and 3.10 years for patients with no history of chemotherapy. History of radiation had no effect on median TTP. Sandostatin LAR (octreotide) was well-tolerated.

Conclusions:This is one of the largest retrospective analysis of meningioma patients treated with Sandostatin LAR (octreotide) suggesting that this treatment has minimal to no adverse events and could prolong overall survival, and progression free survival especially for patients with ER-PR+ tumors who underwent surgeries for small skull-based tumors.

Protein Kinase A Distribution in Meningioma

Deregulation of intracellular signal transduction pathways is a hallmark of cancer cells, clearly differentiating them from healthy cells. Differential intracellular distribution of the cAMP-dependent protein kinases (PKA) was previously detected in cell cultures and in vivo in glioblastoma and medulloblastoma. Our goal is to extend this observation to meningioma, to explore possible differences among tumors of different origins and prospective outcomes. The distribution of regulatory and catalytic subunits of PKA has been examined in tissue specimens obtained during surgery from meningioma patients. PKA RI subunit appeared more evenly distributed throughout the cytoplasm, but it was clearly detectable only in some tumors. RII was present in discrete spots, presumably at high local concentration; these aggregates could also be visualized under equilibrium binding conditions with fluorescent 8-substituted cAMP analogues, at variance with normal brain tissue and other brain tumors. The PKA catalytic subunit showed exactly overlapping pattern to RII and in fixed sections could be visualized by fluorescent cAMP analogues. Gene expression analysis showed that the PKA catalytic subunit revealed a significant correlation pattern with genes involved in meningioma. Hence, meningioma patients show a distinctive distribution pattern of PKA regulatory and catalytic subunits, different from glioblastoma, medulloblastoma, and healthy brain tissue. These observations raise the possibility of exploiting the PKA intracellular pathway as a diagnostic tool and possible therapeutic interventions.

Clinical potential of meningioma genomic insights: a practical review for neurosurgeons

Meningiomas are among the most common intracranial pathological conditions, accounting for 36% of intracranial lesions treated by neurosurgeons. Although the majority of these lesions are benign, the classical categorization of tumors by histological type or World Health Organization (WHO) grade has not fully captured the potential for meningioma progression and recurrence. Many targeted treatments have failed to generate a long-lasting effect on these tumors. Recently, several seminal studies evaluating the genomics of intracranial meningiomas have rapidly changed the understanding of the disease. The importance of NF2 (neurofibromin 2), TRAF7 (tumor necrosis factor [TNF] receptor-associated factor 7), KLF4 (Kruppel-like factor 4), AKT1, SMO (smoothened), PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha), and POLR2 (RNA polymerase II subunit A) demonstrates that there are at least 6 distinct mutational classes of meningiomas. In addition, 6 methylation classes of meningioma have been appreciated, enabling improved prediction of prognosis compared with traditional WHO grades. Genomic studies have shed light on the nature of recurrent meningioma, distinct intracranial locations and mutational patterns, and a potential embryonic cancer stem cell-like origin. However, despite these exciting findings, the clinical relevance of these findings remains elusive. The authors review the key findings from recent genomic studies in meningiomas, specifically focusing on how these findings relate to clinical insights for the practicing neurosurgeon.

Stimulated Raman Histology for Intraoperative Guidance in the Resection of a Recurrent Atypical Spheno-orbital Meningioma: A Case Report and Review of Literature

Meningiomas are the most common intracranial, extra-axial neoplasms and account for a significant proportion of all central nervous system (CNS) tumors. Regardless of the grade, treatment typically involves upfront surgical resection. However, in many instances, especially in meningiomas arising from the skull base, complete removal is often difficult given the close proximity to important anatomic structures. In this report, we discuss the use of stimulated Raman histology as a means to identify tissue boundaries during the resection of an extensive, recurrent, atypical spheno-orbital meningioma.

We report a 75-year-old male with a history of a prior left frontotemporal craniotomy for a grade II meningioma three years prior, who presented with worsening left-sided visual loss and pronounced temporal bossing. Repeat magnetic resonance imaging (MRI) revealed a recurrent left spheno-orbital tumor suggestive of a meningioma extending into the middle cranial fossa, the lateral orbit, and the temporalis muscle. He underwent an extended orbito-pterional craniotomy, and intraoperative stimulated Raman histology aided in the identification of tumor margins within the orbit and the temporalis muscle in order to better preserve the normal orbital contents and muscle bulk of the infratemporal fossa.

This case demonstrates the utility of stimulated Raman histology during the resection of invasive skull base tumors. The immediate intraoperative Raman histologic sections can clearly identify tissue boundaries and thus help preserve important anatomic structures. Continued development of this method can potentially improve the accuracy of intraoperative diagnoses and guide surgeons during tumor resections near eloquent anatomical regions or important normal structures.

Incidence of and risk factors for major complications or death in dogs undergoing cytoreductive surgery for treatment of suspected primary intracranial masses

OBJECTIVE To determine incidence of and risk factors for major complications occurring in dogs within 30 days after cytoreductive surgery performed by a single pair of surgeons for treatment of suspected primary intracranial masses. DESIGN Retrospective cohort study. ANIMALS 160 client-owned dogs that underwent cytoreductive surgery for treatment of suspected primary intracranial masses between January 2009 and December 2015 at a veterinary teaching hospital. PROCEDURES Medical records were retrospectively reviewed for complications occurring within 30 days after surgery. Data (eg, signalment, clinical signs, previous treatments, preoperative neurologic examination findings, neuroanatomical location, time from onset of clinical signs to surgery, surgical approach, and histopathologic diagnosis) were analyzed for associations with death and with development of major complications other than death. RESULTS 21 (13.1%) dogs died (11 during hospitalization and 10 after discharge) and 30 (18.8%) developed major complications other than death during the first 30 days after surgery. Dogs with abnormal preoperative neurologic examination findings were more likely to develop complications or die. Dogs undergoing a suboccipital approach were more likely to die. The most common postoperative complications other than death were seizures (n = 18 [11.3%]), worsening of neurologic status (6 [3.8%]), and aspiration pneumonia (6 [3.8%]). CONCLUSIONS AND CLINICAL RELEVANCE Results of the present study provided valuable information on predisposing factors, odds of major complications or death, and incidences of major complications or death in dogs during the first 30 days after undergoing cytoreductive surgery for treatment of suspected primary intracranial masses. Careful case selection may help improve outcomes and minimize complications.

Clinical Outcomes of Recurrent Intracranial Meningiomas Treated with Proton Beam Reirradiation

Purpose

Recurrent meningiomas remain therapeutically challenging, often progressive despite multimodality salvage. There are limited data guiding reirradiation (reRT), and proton beam radiation therapy (PBRT) offers a potential advantage owing to lower integral brain dose.

Patients and Methods

We retrospectively conducted a review of 16 patients who received PBRT reRT for recurrent meningiomas. Kaplan-Meier and proportional hazards were used to determine post-PBRT progression-free survival (PFS) and overall survival (OS) and to evaluate clinical predictors.

Results

At diagnosis, 7 (44%), 8 (50%), and 1 (6%) patient had World Health Organization (WHO) grade I, II and III tumors, respectively. All received prior radiation therapy (RT) to a median of 54 Gy (range 13-65.5). Median time to PBRT reRT after prior RT was 5.8 years (range 0.7-18.7). Median PBRT dose was 60 Gy(RBE) (range 30-66.6), and median planning tumor volume (PTV) was 76 cm³ (range 8-249). Median follow-up was 18.8 months. At last follow-up, 7 intracranial recurrences (44%) and 3 disease-related deaths (19%) were found. Median cohort PFS was 22.6 months, with 1- and 2-year PFS of 80% and 43%, respectively. Median OS was not achieved, with 1- and 2-year OS of 94% and 73%; all deaths were felt to be related to meningioma. Patients with initially grade I tumors had improved PFS versus higher grade (Hazard Ratio, HR = 0.23, P = .03) with 1- and 2-year PFS estimates of 100% versus 71% and 75% versus 29%, respectively. Longer interval between prior RT and PBRT also predicted improved PFS (P = .03) and OS (P = .049). Overall late grade 3+ toxicity rate was 31%. Two patients (13%) developed radionecrosis at 6 and 16 months after PBRT; only 1 was symptomatic.

Conclusions

This is the first series specifically analyzing PBRT alone as a reRT strategy for recurrent meningioma. We report fair intracranial control with low rates of radionecrosis at 1 year after reRT. However, strategies to achieve durable outcomes are needed, particularly for high-grade tumors.

Mebendazole and radiation in combination increase survival through anticancer mechanisms in an intracranial rodent model of malignant meningioma

PURPOSE

Meningiomas are a frequent tumor of the central nervous system. Although mostly benign, approximately 5% present as atypical or malignant tumors. Treatments for atypical meningiomas include gross total resection and radiotherapy, but about 33% of patients have recurrent tumors, sometimes as a higher grade. Recently, the brain penetrant anthelmintic drug, mebendazole, has shown promise as an anticancer agent in rodent models of glioblastoma and medulloblastoma.

METHODS

The half maximal inhibitory concentration (IC₅₀) effect on colony formation, cell proliferation, and caspase-3/7 markers of apoptosis of mebendazole with and without radiation was measured in vitro. Mice intracranially implanted with KT21MG1 human meningioma were administered mebendazole alone or in combination with radiation. Survival benefit was evaluated, while tumors were investigated by immunohistochemical staining for apoptosis, cell proliferation, and vascular density.

RESULTS

In vitro experiments on meningioma cell lines showed the IC₅₀ for mebendazole in the range of 0.26-0.42 µM. Mebendazole alone induced cytotoxicity, however the combination had a greater reduction in colony formation and resulted in higher levels of cleaved caspase-3. The in vivo study showed both, mebendazole alone and the combination, to have a survival benefit with an increase in apoptosis, and decreases in tumor cell and vascular proliferation.

CONCLUSION

These preclinical findings indicate that mebendazole alone or in combination with radiation can be considered for the treatment of malignant meningioma. The mechanism of action for this combination may include an increase in apoptosis, a reduction in proliferation and angiogenesis, or a combination of these effects.

An overview of meningiomas

Meningiomas are the most common primary intracranial tumor. Important advances are occurring in meningioma research. These are expected to accelerate, potentially leading to impactful changes on the management of meningiomas in the near and medium term. This review will cover the histo- and molecular pathology of meningiomas, including recent 2016 updates to the WHO classification of CNS tumors. We will discuss clinical and radiographic presentation and therapeutic management. Surgery and radiotherapy, the two longstanding primary therapeutic modalities, will be discussed at length. In addition, data from prior and ongoing investigations of other treatment modalities, including systemic and targeted therapies, will be covered. This review will quickly update the reader on the contemporary management and future directions in meningiomas. [Formula: see text].

Recent advances in managing/understanding meningioma

Meningiomas are the most common adult primary intracranial tumor. Despite their higher incidence, there have not—until recently—been as many advances in understanding and managing meningiomas. Thus far, two broad classes of meningiomas have emerged on the basis of their mutational profile: those driven by neurofibromatosis 2 (NF2) inactivation and those with non-NF2 driver gene alterations, such as mammalian target of rapamycin and Hedgehog, Wingless/b-catenin, Notch, transforming growth factor-b receptor, mitogen-activated protein kinase, and phospholipase C pathway alterations. In addition to improvements in molecular diagnostics, advances in imaging are being studied to better predict tumor behavior, stratify risk, and potentially monitor for disease response. Management consists primarily of surgery and radiation therapy and there has been limited success from medical therapies, although novel targeted agents are now in clinical trials. Advances in imaging and understanding of the genetic makeup of meningiomas demonstrate the huge potential in revolutionizing the classification, diagnosis, management, and prognosis of meningiomas..

Accuracy of Raman spectroscopy in differentiating brain tumor from normal brain tissue

Raman spectroscopy could be applied to distinguish tumor from normal tissues. This meta-analysis was conducted to assess the accuracy of Raman spectroscopy in differentiating brain tumor from normal brain tissue. PubMed and Embase were searched to identify suitable studies prior to Jan 1st, 2016. We estimated the pooled sensitivity, specificity, positive and negative likelihood ratios (LR), diagnostic odds ratio (DOR), and constructed summary receiver operating characteristics (SROC) curves to identity the accuracy of Raman spectroscopy in differentiating brain tumor from normal brain tissue. A total of six studies with 1951 spectra were included. For glioma, the pooled sensitivity and specificity of Raman spectroscopy were 0.96 (95% CI 0.94-0.97) and 0.99 (95% CI 0.98-0.99), respectively. The area under the curve (AUC) was 0.9831. For meningioma, the pooled sensitivity and specificity were 0.98 (95% CI 0.94-1.00) and 1.00 (95% CI 0.98-1.00), respectively. The AUC was 0.9955. This meta-analysis suggested that Raman spectroscopy could be an effective and accurate tool for differentiating glioma and meningioma from normal brain tissue, which would help us both avoid removal of normal tissue and minimize the volume of residual tumor.

Microvascularization of Grade I meningiomas: effect on tumor volume, blood loss, and patient outcome

OBJECTIVE Quantitative assessment of tumor microvascularity has the potential to improve prognostication, advance understanding of tumor biology, and help narrow potential molecular therapies. While the role of tumor microvascularity has been widely studied in meningiomas, this study examines both the role of automated measurements and the impact on surgical outcome. METHODS Two hundred seven patients with Grade I meningiomas underwent surgery between 1996 and 2011. Tissue samples from each patient were retrospectively evaluated for histopathological measures of microvascularity, including staining for von Willebrand factor (vWF), CD31, CD105, hypoxia-inducible factor 1 (HIF-1), vascular endothelial growth factor, glucose transporter 1, and carbonic anhydrase IX. Manual methods of assessing microvascularity were supplemented by a computational analysis of the microvascular patterns by means of fractal analysis. MIB-1 proliferation staining was also performed on the same tumors. These measures were compared with various patient characteristics, tumor volume, estimated blood loss (EBL) during surgery, progression-free survival (PFS), and overall survival (OS). RESULTS The mean patient age was 55.4 ± 14.8 years, and 63 (30.4%) patients were male. Patients harboring tumors ≥ 3 cm were significantly older (56.9 ± 15.2 years vs 53.1 ± 13.6 years; p = 0.07), more frequently male (40.8% vs 14.6%; p = 0.0001), and had greater EBL (446.5 ± 532.2 ml vs 185.4 ± 197.2 ml; p = 0.0001), greater tumor volume (33.9 ± 38.1 ml vs 29.4 ± 23.5 ml; p = 0.0001), higher MIB-1 index values (3.0% ± 5.4% vs 1.7% ± 1.7%; p = 0.03), higher vWF levels (85.6% ± 76.9% vs 54.1% ± 52.4%; p = 0.001), lower HIF-1 expression (1.4 ± 1.3 vs 2.2 ± 1.4; p = 0.004), and worse OS (199.9 ± 7.6 months vs 180.8 ± 8.1 months; p = 0.05) than patients with tumors < 3 cm. In the multivariate logistic regression, MIB-1 (OR 1.14; p = 0.05), vWF (OR 1.01; p = 0.01), and HIF-1 (OR 1.54; p = 0.0001) significantly predicted tumor size. Although multiple factors were predictive of EBL in the univariate linear regression, only vWF remained significant in the multivariate analysis (β = 0.39; p = 0.004). Lastly, MIB-1 was useful via Kaplan-Meier survival analysis for predicting patients with disease progression, whereby an MIB-1 cutoff value of ≥ 3% conferred a 36% sensitivity and 82.5% specificity in predicting disease progression; an MIB-1 value ≥ 3% showed significantly shorter mean PFS (140.1 ± 11.7 months vs 179.5 ± 7.0 months; log-rank test, p = 0.05). The Cox proportional hazards model showed a trend for MIB-1 in predicting disease progression in a hazards model (OR 1.08; 95% CI 0.99-1.19; p = 0.08). CONCLUSIONS These results support the importance of various microvascularity measures in predicting preoperative (e.g., tumor size), intraoperative (e.g., EBL), and postoperative (e.g., PFS and OS) outcomes in patients with Grade I meningiomas. An MIB-1 cutoff value of 3% showed good specificity for predicting tumor progression. The predictive ability of various measures to detect aberrant tumor microvasculature differed, possibly reflecting the heterogeneous underlying biology of meningiomas. It may be necessary to combine assays to understand angiogenesis in meningiomas.

Genetic variants and increased risk of meningioma: an updated meta-analysis

PURPOSE

Various genetic variants have been reported to be linked to an increased risk of meningioma. However, no confirmed conclusion has been obtained. The purpose of the study was to investigate potential meningioma-associated gene polymorphisms, based on published evidence.

MATERIALS AND METHODS

An updated meta-analysis was performed in September 2016. After electronic database searching and study screening, we selected eligible case-control studies and extracted data for meta-analysis, using Mantel-Haenszel statistics. P-values, pooled odds ratios (ORs), and 95% confidence intervals were calculated.

RESULTS

We finally selected eight genes with ten polymorphisms: MLLT10 rs12770228, CASP8 rs1045485, XRCC1 rs1799782, rs25487, MTHFR rs1801133, rs1801131, MTRR rs1801394, MTR rs1805087, GSTM1 null/present, and GSTT1 null/present. Results of meta-analyses showed that there was increased meningioma risk in case groups under all models of MLLT10 rs12770228 (all OR >1, P<0.001), compared with control groups. Similar results were observed under the allele, homozygote, dominant, and recessive models of MTRR rs1801394 (all OR >1, P<0.05), and the heterozygote and dominant models of MTHFR rs1801131 in the Caucasian population (all OR >1, P<0.05). However, no significantly increased meningioma risks were observed for CASP8 rs1045485, XRCC1 rs25487, rs1799782, MTHFR rs1801133, MTR rs1805087, or GSTM1/GSTT1 null mutations.

CONCLUSION

Our updated meta-analysis provided statistical evidence for the role of MLLT10 rs12770228, MTRR rs1801394, and MTHFR rs1801131 in increased susceptibility to meningioma.