The role of stereotactic radiosurgery in the management of benign, atypical, and malignant meningiomas

Stereotactic radiosurgery and fractionated stereotactic radiotherapy (SR) offer precise localization of radiation dose (Gy) for the treatment of meningioma (M). For the multimodal treatment with preservation of function, SR is complementary to both microsurgery (S) and conventional external beam radiotherapy (XRT). The role of SR in the management of atypical and malignant meningiomas, however, remains unexplored. Fifty consecutive patients with meningioma: 18 males (60.1 +/- 2.3 years) and 32 females (56.9 +/- 2.2 years) (p = NS) received SR. Thirty-one patients had surgery 69.6 +/- 13.9 months (95% CI: 53.3-98.0) prior to SR. For patients having S, the incidence of atypical or malignant versus benign meningiomas (14 versus 17 patients) increased with age (p = 0.03). Twenty patients had XRT approximately 18 months prior to SR. For antecedent XRT, the range of doses was 3600-6400 cGy (median: 5040 cGy). Following failure of S and/or XRT, patients had SR. Compared to other series, the mean tumor volumes for SR were comparatively large: 9.8 +/- 1.3 cm³ (range 0.3-37.1 cm³). The median SR dose was 3500 cGy (range 540-5400 cGy) administered in seven fractions (range 1-30). Linear regression analysis showed a consistent method for fractionation: the number of administered fractions increased (p = 0.053) and the total dose increased (p = 0.054) with tumor size. During the interval for follow-up (17.9 +/- 2.9 months), one patient with malignant meningioma required surgery for progression 8 months after SR. In the remaining patients, post-SR MRIs showed control (unchanged or smaller tumor volume) regardless of histology. These results show that SR may provide control of M regardless of grade.