Elsevier

World Neurosurgery

Volume 144, December 2020, Pages e53-e61
World Neurosurgery

Original Article
Stereotactic Radiosurgery for Atypical and Anaplastic Meningiomas

https://doi.org/10.1016/j.wneu.2020.07.211Get rights and content

Background

Although most meningiomas will be benign, a small proportion will have atypical or anaplastic histologic features and will exhibit more aggressive behavior. The treatment of these tumors has been controversial, especially for patients with recurrence after resection and radiotherapy. We have presented a large series of atypical and anaplastic meningiomas treated with stereotactic radiosurgery (SRS).

Methods

We performed a retrospective review of a single-institution radiosurgery database and identified 48 patients with 183 lesions who had undergone 99 SRS sessions from 1999 to 2019. The median dose was 15 Gy prescribed to the 50% isodose line. The center of the failures was plotted, and the distance from the treated tumor to the center of the failure was measured. Simulated treatment volumes for external beam radiotherapy were generated according to the target, and failures were characterized as local, marginal, or distant according to the simulated volume.

Results

The 5-year disease-free and overall survival rate measured from the initial SRS session was 45.8% and 74.7%, respectively. The 5-year lesional control rate was 68.9%. The most common pattern of first failure was isolated distant failure, followed by isolated local or marginal failure. The incidence of distant failure was significantly greater after treatment of >2 lesions in a single SRS session. Isolated local/marginal failure was associated with grade III tumors and an increasing tumor size.

Conclusions

High-risk meningiomas are a heterogeneous group of tumors with a propensity for multiple failures. The most common pattern of relapse after SRS was distant. However, local control remains an issue. Further studies evaluating dose-escalation strategies are warranted.

Introduction

Meningiomas are common intracranial tumors. Most will be World Health Organization (WHO) grade I and considered benign. However, a smaller proportion of meningiomas will be higher grade, either WHO grade II (atypical), which formerly accounted for 7% of all meningiomas, or WHO grade III (anaplastic), which account for 3% of all meningiomas.1 Because of the changes in the WHO criteria for the pathologic diagnosis of grade II tumors, the incidence of grade II meningioma has been increasing, with some series reporting >30% of meningiomas as atypical.2 Although patients with grade I meningiomas will generally have excellent outcomes after surgery or radiotherapy (RT) alone, grade II and grade III meningiomas will behave more aggressively and commonly lead to morbidity and mortality.1 The management of these tumors has been somewhat controversial; however, increasing data have suggested a benefit from the use of adjuvant RT.3,4

The Radiation Therapy Oncology Group (RTOG) 0539 study is a recently reported phase II trial that investigated the use of adjuvant RT for meningioma.5 Patients with high-risk tumors (any recurrent WHO grade II; new grade II tumors without gross total resection; and any WHO grade III tumors) were assigned to receive adjuvant RT. Adjuvant RT consisted of 54 Gy the tumor bed plus a 2-cm margin and a simultaneous integrated boost to 60 Gy to the tumor bed plus a 1-cm margin. More than 90% of the cases of tumor progression within 3 years occurred inside the 54-Gy volume.5

The high rates of in-field progression seen in the RTOG 0539 trial have raised questions regarding the need for the large margins used in the study and the potential role of further dose escalation to smaller fields. Previous reports of stereotactic radiosurgery (SRS) for atypical meningioma have reported a dose–response relationship in which escalating doses were associated with local control.6, 7, 8 However, a greater incidence of marginal failure has been reported with SRS for atypical meningioma, with 1 series reporting a 17% marginal failure rate, which was defined as within 2 cm of the radiosurgical volume.6 Moreover, 1 series reported that the local control benefit seen with adjuvant RT for grade II meningioma was limited to those who had received external beam RT (EBRT) instead of more focused adjuvant SRS.9 No clear consensus has been reached on the optimal treatment of patients with recurrent meningioma who have previously undergone RT. In the present report, we have described a large, retrospective cohort of patients with high-risk meningioma treated with SRS with the patterns of failure determined with respect to a hypothetical fractionated RT volume using the RTOG 0539 guidelines.

Section snippets

Data Collection

A retrospective review of our institutional gamma knife database revealed 48 patients who had undergone 99 individual SRS sessions for pathologically confirmed WHO grade II or III meningioma from 1999 to 2019. Of these 48 patients, the clinical outcomes have been previously reported for 24.6 A new meningioma that had developed in a patient with a pathologically confirmed WHO grade II or III meningioma was presumed to be of the same grade and characteristics as the previous tumor. The patient

Patient Characteristics

Baseline patient and SRS session level characteristics are depicted in Table 1. The median age at the first SRS session was 61 years (range, 2–89 years). Of the 48 patients, 29 (60%) patients were female and 19 (40%) were male. Neurofibromatosis was present in 3 (6%) and radiation-induced meningioma was present in 3 (6%). A total of 99 SRS sessions were included in the present analysis. The median number of SRS sessions per patient was 1 (range, 1–7), and median number of lesions treated per

Discussion

The ideal management of atypical and anaplastic meningiomas has remained unclear. RT has been commonly used, both as adjuvant treatment after surgical resection and definitively for unresectable disease. However, the ideal margins for RT have not been well defined. In the present report, we have described a large series of high-risk meningiomas treated with SRS.

Conclusions

High-risk meningiomas are a heterogeneous group of tumors with a propensity for multiple recurrences. Although the treatment of these tumors with SRS has been classically associated with marginal failure, failure outside a simulated adjuvant RT field are also common, especially for patients with >2 lesions treated in a single SRS session. Local and marginal failure remains an issue; thus, radiation dose escalation, such as combining EBRT with an SRS boost to a limited volume would be worthy of

CRediT authorship contribution statement

Corbin A. Helis: Conceptualization, Methodology, Investigation, Writing - original draft, Data curation, Visualization. Ryan T. Hughes: Conceptualization, Methodology, Formal analysis, Data curation, Writing - review & editing. Christina K. Cramer: Conceptualization, Writing - review & editing. Stephen B. Tatter: Conceptualization, Writing - review & editing. Adrian W. Laxton: Conceptualization, Writing - review & editing. J. Daniel Bourland: Conceptualization, Writing - review & editing.

References (19)

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The views and information presented are those of the authors and do not represent the official position of the U.S. Army Medical Center of Excellence, the U.S. Army Training and Doctrine Command, or the Departments of Army, Department of Defense, or U.S. Government.

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