Stereotactic Radiosurgery for Intracranial Meningiomas: A 15 Year Experience

This study aims to report long-term clinical outcomes after Gamma knife radiosurgery (GKRS) for intracranial meningiomas. In this IRB approved study, we reviewed the records of all patients with meningiomas treated with GKRS between 1998 and 2014. GKRS treatment planning and delivery was performed according to standard protocols. The median GKRS dose was 14 Gy (SD ± 1.9) prescribed to the 50% isodose line. A total of 470 meningiomas in 391 patients were treated consecutively during this 15 years period; 427 meningiomas were included & 35 patients (43 meningiomas) were excluded being lost to follow up. Median age was 60 years, 59.8% had prior surgery, and 32% were males. Tumor sites included anterior (14%), middle (14%), & posterior (30%) cranial fossae, convexity (25%), parasagittal (10%), temporal (5%), & others (2%). Of 201 tumors with available histopathology; 36.3%, 47.8%, & 15.9% were grades 1, 2, & 3, respectively. Mean tumor size was 5.73 cm3 (median 2.5). Among 52.7% symptomatic patients, most common symptoms were headache (23%), visual impairment (11%), hearing deficit (7%), and motor deficits (7%). After a mean follow up of 51 months (range 3 – 188m), the local recurrence rate was 14.5% of all treated meningiomas (13% of the patients). The mean time to recurrence was 33 months (range 2 – 134). The 3, 5, & 10-year actuarial local control (LC) rates were 86.7%, 82.0%, & 71.2%, respectively. The 3, 5, & 10-years overall survival (OS) was 92.7%, 87.9%, & 66.8%, respectively. In univariate analysis: Females had higher LC (HR 0.407, P=0.00004); Non-white race (HR 1.804, P=0.03), larger tumor size (HR 1.039, P <0.0001), grade 2 (HR 5.496P <0.0001), and grade 3 tumors (HR 6.53, P <0.0001) had worse LC; Higher GKRS doses were associated with superior OS (HR 0.808, P= 0.01); Older age (HR 1.058, P <0.00021), non-white race (HR 2.508, P=0.0006), and larger tumor size (HR 1.022, P=0.009) were associated with inferior OS. Multivariate analysis revealed: Significantly worse LC in non-white race (HR 4.629, P=0.0004), larger tumor size (HR 1.049, P <0.0001), grade 2 (HR 7.160, P <0.0001), and grade 3 tumors (HR 16.635, P <0.0001); significantly inferior OS in older age (HR 1.060, P <0.0001), non-white race (HR 2.844, P =0.0001); significantly superior OS in females (HR 0.473, P = 0.006). The most common acute toxicities after GKRS were headache (3.6%), visual impairment (3.6%), and dizziness (1.1%). Chronic toxicities included, headache (3%), visual impairment (2.5%) and two patients (0.5%) developed GKRS-induced radiation necrosis. There were no second malignant tumors noted in our series. This report, one of the larger GKRS series for meningiomas, demonstrates that GKRS is a safe and effective treatment modality for these patients with durable tumor control and minimal toxicity.