Stereotactic Radiosurgery for Atypical and Anaplastic Meningiomas.

Abstract Background While most meningiomas are benign, a small proportion have atypical or anaplastic histology, and exhibit more aggressive behavior. Treatment of these tumors is controversial, particularly for patients who recur after resection and radiation therapy. Here we present a large series of atypical and anaplastic meningiomas treated with stereotactic radiosurgery. Methods Retrospective review of a single institution radiosurgery database identified 48 patients with 183 lesions in 99 SRS sessions treated from 1999 to 2019. The median dose was 15 Gy prescribed to the 50% isodose line. The center of failures were plotted and the distance from the treated tumor to the center of the failure was measured. Simulated treatment volumes for external beam radiation were generated based on the target, and failures were characterized as local, marginal, or distant based on the simulated volume. Results 5 year disease-free and overall survival measured from initial SRS were 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/marginal failure. Distant failure was significantly higher after treatment of more than 2 lesions in a single SRS session. Isolated local/marginal failure was associated with Grade III tumors and 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 is distant, however local control remains an issue. Further study evaluating dose escalation strategies may be warranted.