Observation or Radiation Therapy in Treating Patients With Grade I, Grade II, or Grade III Meningioma

OBJECTIVES: Primary * To estimate the rates of progression-free survival at 3 years in patients with low-risk meningioma undergoing observation and in patients with intermediate- or high-risk meningioma undergoing radiotherapy. Secondary * To study the concordance, or lack thereof, between central and parent institution histopathologic diagnosis, grading, and subtyping. * To estimate the rates of overall survival at 3 years in these patients. * To estimate the incidence rates of acute and late adverse events ≥ grade 2 in patients with intermediate- or high-risk meningioma undergoing radiotherapy. * To evaluate MRI imaging predictors by central neuroradiology review at diagnosis, at any failure, and at 3 years. * To evaluate adherence to protocol-specific target and normal tissue radiotherapy parameters. This is a multicenter study. Patients are assigned to 1 of 3 groups according to risk. After completion of study treatment, patients are followed up every 3-6 months for 3 years and then annually for 10 years.