Atypical and malignant meningiomas treated with stereotactic irradiation

Introduction: Atypical and malignant meningiomas are at high risk of local failure and regional progression. The role of Stereotactic irradiation for local control and regional progression free survival in the brain were evaluated in this retrospective study. Methods: Of all meningiomas treated with Stereotactic irradiation from 1991-2002, 40 tumors in 21 patients were confirmed as atypical or malignant in the UCLA pathology record. 45% (18 tumors in 13 patients) were classified as atypical and 55% (22 tumors in 8 patients) were malignant. Follow-up was available in 19/21 patients (median 16 mo). All patients had undergone previous resection. 78% of tumors were treated with Stereotactic radiosurgery (dose range 1400-1800 cGy; isodose 50-90%) and 22% were treated with Stereotactic radiotherapy (dose range 2500 cGy in 5 fxns to 5400 in 30 fxns; isodose 85-90%). There were 11 female and 10 male patients. Results: The actuarial regional progression free survival was significantly better for atypical vs. malignant meningioma (P = 0.006, Kaplan-Meier, Log Rank Test). At last follow up crude regional progression free survival was 47% for atypical and 11% for malignant meningioma. Also, there was a trend for increased local control in atypical vs. malignant meningioma (P = 0.09, Kaplan-Meier, Log Rank Test). At last follow-up local control was achieved in 47% of atypical and 33% malignant meningioma. There was no statistical difference in local control or regional progression free survival between patients treated with SRS or SRT. Conclusion: Local and regional control rates were modest in our series. However, with atypical meningioma, local control did translate into regional progression free survival (47% local control, 47% regional progression free survival). Therefore, because of the ability to add a margin and safely treat larger areas at risk for tumor, SRT should be the modality of choice for atypical and malignant meningioma.