Stereotactic Radiosurgery for Atypical and Anaplastic Meningiomas

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).

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.

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.

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.