Atypical and Anaplastic Meningiomas: Comparison of Outcomes Between Photon and Proton Radiation Therapy

Abstract

Purpose/Objective(s): To compare clinical outcomes in patients with grade 2 and 3 meningiomas treated with photon or proton radiation therapy (RT). Materials/Methods: Retrospective review of 42 patients with grade 2 (nZ36) or grade 3 (nZ6) meningiomas treated with photon (nZ16) or proton (nZ26) RT from 2005e2014. The median patient age was 58.3 years (range 14e75) for the entire cohort. Twenty-seven patients were treated adjuvantly and 15 at the time of disease progression with a median interval from surgery to RT of 2 months and 21.5 months, respectively. Two patients were treated with stereotactic radiosurgery with median dose of 15.5 Gy to the 50% isodose line, while the remainder received conventionally fractionated therapy. The median tumor volume at time of RT was 5.3 cc. There was no statistical difference between the two RT modality cohorts by patient gender, tumor location, indication for RT, number of prior meningioma surgeries, or tumor volume at the time of RT. The median fractionated RT dose was 63 Gy (RBE) (range 54e68.4) for proton therapy and 59.4 Gy (range 54e68.4) for photon therapy (p 60 Gy (pZ0.06). On multivariate analysis, negative prognostic factors for local recurrence were grade 3 tumor histology (hazard ratio (HR) 20.1, 95% CI 3.3e121.3, pZ0.001), tumor volume larger than the median volume of 5.3 cc (HR 5.1, 95% CI 1.2e21.2, pZ0.025), and radiation dose 60 Gy (HR 4.8, 95% CI 1.2e20.0, pZ0.03). The 2-year overall survival (OS) for the entire cohort was 91.8% (95% CI 82.8e100%). On univariate analysis, tumor grade was the only variable significantly associated with OS (grade 3 HR for death 42.9, 95% CI 5.8e319.5, p 60 Gy was associated with improved local control on multivariate analysis. Prospective studies are needed to define the optimal radiation dose for high-grade meningiomas. Author Disclosure: T.M. Hansen: None. G.K. Bartlett: None. K.P. McMullen: None. M.W. McDonald: None.