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A Comparison of Single Fraction Radiosurgery Tumor Control and Toxicity in the Treatment of Basal and Nonbasal Meningiomas

Between July 1993 and October 1997, 107 patients with 118 meningiomas were treated with Gamma Knife radiosurgery (GKRS). The most frequent site of tumor origin was the skull base (54%). The mean tumor diameter and volume were 2.5 cm and 9.4 cm3, respectively. The mean dose to the tumor periphery was 17 Gy, prescribed to a mean iso-dose of 47%. At a mean follow-up of 28 months, tumor control for basal and nonbasal meningiomas was 80%. Deteriorating peritumoral edema associated with symptoms was observed in 1 of 49 (2%) skull-base tumors and in 4 of 39 (10%) non-basal tumors, without associated tumor growth. (p=0.l5 and 0.234 respectively, z-test). Stereotactic radiosurgery can achieve acceptable tumor control with low morbidity in the treatment of most meningiomas. However, when the tumor is nonbasal, the potential morbidity from peritumoral edema should be recognized and other treatment options considered, such as adjuvant surgery, partial fractionated irradiation or stereotactic radiotherapy.