Management of atypical and malignant meningiomas: role of high-dose, 3D-conformal radiation therapy

Objective Atypical and malignant meningiomas are at high risk for local failure. The role of radiation therapy (RT) and dose levels required to improve tumor control are poorly defined. This study reviews our experience with RT. Material and methods Thirty-one patients underwent fractionated RT for atypical (AM, 15 patients) or malignant meningioma (MM, 16 patients) of the cranium. Sixteen patients presented with primary and 15 with recurrent disease. Eight patients received RT following total resection, 21 patients after subtotal resection and 2 patient following biopsy only. RT was given using megavoltage photons in 15 patients and combined photons and 160 MeV protons in 16 patients. Total target doses ranged from 50 to 68 (AM, mean 62) and from 40 to 72 (MM, mean 58) Gy or CGE (= cobalt-gray-equivalent). Results With mean observation time of 59 months (range: 7-155 months) actuarial local control rates at 5- and 8-years were similar for both histologies (38% and 19% for AM and 52 and 17% for MM). However, significantly improved local control was observed for proton versus photon RT (80% versus 17% at 5 years, p = 0.003) and target doses greater than or equal to 60 Gy for both, atypical (p = 0.025) and malignant meningioma (p = 0.0006). At time of analysis, 14/15 patients (93%) with AM and 6/16 (38%) with MM were alive. Three patients (19%) with MM developed distant metastasis. Actuarial 5- and 8-year survival rates for MM were significantly improved by use of proton over photon RT and radiation doses greater than or equal to 60 CGE. Three patients developed symptomatic radiation damage after 59.3, 68.4 and 72 Gy/CGE. Conclusion Conformal, high dose RT resulted in significant improvement of local control for atypical and malignant meningiomas. Increased local control resulted also in improved rates of survival for patients with malignant meningioma.