Observation or Radiation Therapy in Treating Patients With Newly Diagnosed Grade II Meningioma That Has Been Completely Removed by Surgery

PRIMARY OBJECTIVE: I. To determine the extent of clinical benefit of the addition of adjuvant radiotherapy (RT) to gross total resection (GTR) for patients with newly diagnosed World Health Organization (WHO) grade II meningioma. SECONDARY OBJECTIVES: I. Overall survival (OS). II. Disease-specific survival (DSS). III. Toxicity (grade 3+, exclusive of expected alopecia). IV. Neurocognitive function (NCF). V. Patient reported outcomes (PRO) measurements. VI. Adherence to protocol-specific target and normal tissue parameters. VII. Concordance measurements of central versus parent-institution pathology. VIII. Assessment of pHH3 mitotic index and its correlation with progression-free survival (PFS) and OS. IX. Validation of the prognostic value of a 34-gene expression biomarker. X. Validation of the predictive value of a 34-gene expression biomarker in predicting the benefit of radiotherapy. XI. Tissue and specimen collection for future translational research. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients undergo observation. Additionally, patients undergo magnetic resonance imaging (MRI) and blood collection throughout the study. ARM II: Patients undergo intensity-modulated radiation therapy (IMRT) or proton beam radiation therapy 5 days a week over 6.5-7 weeks for a total of 33 fractions in the absence of disease progression or unacceptable toxicity. Additionally, patients undergo MRI and blood collection throughout the study. After completion of study treatment, patients are followed up at 3, 6, and 12 months, every 6 months for year 2 and 3, then yearly for 10 years.