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.

Bevacizumab in refractory higher-grade and atypical meningioma: the current state of affairs

INTRODUCTION

Historically, systemic agents had shown limited efficacy in meningioma, at the expense of significant pharmacologic and/or financial toxicity. As meningiomas are highly vascularized, they might derive benefit from antiangiogenic therapy.

AREAS COVERED

This review summarizes the literature regarding bevacizumab pharmacology, safety and efficacy in patients with refractory meningioma. We have searched PubMed/Medline database for pertinent articles published from inception to 1 September 2018.

EXPERT COMMENTARY

Results of two prospective phase II trials, supported by several retrospective cohorts, suggest a clinical benefit for the vascular endothelial growth factor inhibitor bevacizumab in meningiomas refractory to surgery and radiation therapy. This agent has a tolerable toxicity profile and seems more effective in higher-grade histologies and atypical meningioma, although responses in low-grade meningiomas have also been documented. Our conclusions are restricted due to a small size and lack of control in the prospective trials as well as the retrospective design of other studies. Further study of bevacizumab in refractory higher-grade meningiomas seems warranted.

Systemic therapy for relapsed/refractory meningioma: Is there potential for antiangiogenic agents?

Effective therapies for relapsed/refractory meningioma after surgery and radiation therapy represent an unmet need. Most meningiomas are highly vascularized tumors and, therefore, potentially amenable to antiangiogenic therapy. Herein, we review comprehensively the scientific literature on systemic therapy options for relapsed, persistent or metastatic meningioma, not amenable to local therapy. Also, this review offers insights into the function of vascular endothelial growth factor/receptor pathway both in health and disease. Further, we address the current status of the preclinical and clinical studies targeting vascular endothelial growth factor/receptor signaling in meningioma. Most relevant publications were identified through searching the PubMed/Medline database for articles published from inception to 1 February 2018. Vascular endothelial growth factor pathway activation might represent the primary driver of angiogenesis in meningioma. Positive findings of two prospective phase II trials, supported by the results of several retrospective cohorts, suggest a clinical benefit for the vascular endothelial growth factor inhibitor bevacizumab in refractory meningioma. Bevacizumab causes both peritumoral brain edema reduction and true meningioma shrinkage. Patients with WHO grades II-III meningioma appear to benefit more than patients with grade I disease. Similarly, responses have been documented with certain oral targeted anti-vascular endothelial growth factor/receptor agents. Further exploration of the role of vascular endothelial growth factor/receptor inhibitors in refractory meningioma seems warranted.

Bevacizumab therapy for adults with recurrent/progressive meningioma: a retrospective series

Intracranial meningiomas are often indolent tumors which typically grow over years to decades. Nonetheless, meningiomas that progress after maximum safe resection and radiation therapy pose a significant therapeutic challenge and effective therapies have yet to be identified. Preclinical studies implicate angiogenesis in the pathophysiology of more aggressive meningiomas, suggesting that anti-angiogenic therapies may be of utility in this setting. We performed a retrospective review of fourteen patients with recurrent meningioma treated at Duke University Medical Center with bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor, administered either alone or in combination with chemotherapy. Most patients were heavily pre-treated. Progression-free survival at 6 months was 86 % and was comparable regardless of meningioma grade and whether bevacizumab was administered as monotherapy or in combination with chemotherapy. Most toxicities were mild however single patients developed CNS hemorrhage (grade 1) and intestinal perforation (grade 4), respectively. Bevacizumab can be administered safely to patients with meningioma and appears to be associated with encouraging anti-tumor effect when administered as either a single agent or in combination with chemotherapy. Phase II trials investigating bevacizumab in patients with progressive/recurrent meningioma are warranted.

Adult primary intradural spinal cord tumors: a review

Primary spinal cord tumors constitute 2% to 4% of all central nervous system neoplasms and are characterized based on their location as intramedullary, intradural extramedullary, and extradural. A contemporary literature review of primary intradural spinal cord tumors was performed. Among intramedullary tumors, ependymomas are more common and often can be surgically resected. However, astrocytomas infiltrate the spinal cord and complete resection is rare. Intradural extramedullary tumors include schwannomas, neurofibromas, and meningiomas and are usually amenable to surgical resection. Radiotherapy is reserved for malignant variants and recurrent gliomas, whereas chemotherapy is administered for recurrent primary spinal cord tumors without surgical or radiotherapy options. Early recognition of the signs and symptoms related to primary spinal cord tumors facilitates timely discovery, treatment, potentially minimizes neurologic morbidity, and may improve outcome. Treatment consists of surgical resection, and predictors of outcome include preoperative functional status, histologic grade of tumor, and extent of surgical resection.

Meningiomas

OPINION STATEMENT

Meningiomas are extra-axial dural-based tumors. They are the most common intracranial tumors, occur in mid to late life, and have a female predilection. Symptoms are a function of location. Meningiomas are usually benign, but atypical and malignant forms exist. Treatment is indicated for symptomatic lesions or when neurologic symptoms may shortly occur. Surgical resection can be curative; however, because of their location, some lesions are amenable only to partial resection. Radiation therapy is used for incompletely removed symptomatic lesions, lesions that are not surgically accessible, and small symptomatic lesions. For higher grade meningiomas, radiation is used after surgery. For lesions that recur or grow despite surgery and radiation, systemic chemotherapy can be tried. There is no optimal agent, but hydroxyurea is used most often with very modest success; hormonal approaches have not been successful. Targeting somatostatin receptors or receptor tyrosine kinases using novel agents appears to have some activity and is an area of clinical research.

Adult primary spinal cord tumors

Primary spinal cord tumors represent 2-4% of all neoplasms of the CNS. Primary spinal cord tumors are anatomically separable into two broad categories: intradural intramedullary and intradural extramedullary. Intramedullary tumors are comprised predominantly of gliomas (infiltrative astrocytomas and ependymomas). Resective surgery can usually be accomplished with spinal ependymomas owing to separation of tumor from spinal cord and, when complete, require no further therapy. By contrast, spinal cord gliomas infiltrate the myelon and, consequently, surgery is nearly always incomplete. Involved-field radiotherapy is most often administered after partial resection. Intradural extramedullary tumors are either peripheral nerve sheath tumors (neurofibromas or schwanommas) or meningiomas. In either instance, complete resection may be accomplished and is often curative. Radiotherapy is reserved for rare malignant variants and for patients in whom surgery is contraindicated. Chemotherapy is administered for recurrent primary spinal cord tumors without other options, that is, reoperation or re-irradiation. Problematic, however, is the lack of clinical trials in general for these CNS tumors and for spinal cord tumors in particular. Consequently, treatment is similar to that for intracranial tumors with a similar histology. Early recognition of the signs and symptoms of primary spinal cord tumors allows for early treatment, potentially minimizes neurologic morbidity and improves outcome. Primary treatment is surgery in essentially all spinal cord tumors, and predictors of outcome include preoperative functional status, histological grade of tumor and extent of surgical resection.