Inclusion Criteria:

• PRIOR TO STEP 1 REGISTRATION:
• The patient must have a newly diagnosed unifocal intracranial meningioma, gross totally resected, and histologically confirmed as WHO grade II based upon pathology findings at the enrolling institution; WHO grade will be assigned according to WHO 2016 criteria
• Gross total resection (GTR) will be interpreted as modified Simpson grade 1-3 without gross residual dural-based or extradural tumor; GTR must be confirmed both by modified Simpson grade and by post-operative magnetic resonance imaging (MRI) findings
• Step 1 registration must occur within 180 days of the initial surgery; within this 180 day interval, a second surgery is permitted in order to achieve GTR, but even with a second surgery, step 1 registration must occur within 180 days of the initial resection
• For step 1 registration the operating neurosurgeon must provide the modified Simpson grade
• GTR must be confirmed on post-operative imaging following the most recent surgery; submission of both pre-operative and post-operative MRIs is required for patients; if a second surgery is performed, submission of post-operative MRI is required and pre-operative MRI is required only if obtained; all sequences obtained in the preand post-operative MR imaging are to be submitted to National Radiology Group (NRG) Oncology for study registration; imaging subsequent to enrollment must include pre and post gadolinium contrast-enhanced three-dimensional spoiled gradient (SPGR), magnetization-prepared rapid gradient echo (MP-RAGE), or turbo field echo (TFE) MRI scan and an axial T2 fluid attenuated inversion recovery (FLAIR) sequence; to yield acceptable image quality, the gadolinium contrast-enhanced three-dimensional SPGR, MP-RAGE, or TFE axial MRI scan should use the smallest possible axial slice thickness not exceeding 1.5 mm; the post-operative MRI must be completed within sufficient time to permit step 1 registration within 180 days of the initial resection; these same conditions apply in the setting of a second surgical procedure, although if a second surgery is completed, step 1 registration must still occur with 180 days of initial surgery; computed tomography (CT) imaging is not required, but may be obtained if desired clinically, for instance to assess calcifications or hyperostosis
• The patient or a legally authorized representative must provide study-specific informed consent prior to study entry
• If the patient is a primary English speaker, the patient must participate in the NCF and patient reported outcomes part of the study; if the patient is a primary French or Spanish speaker, the patient must participate in the patient reported outcomes part of the study
• NOTE: Central pathology review must occur between steps 1 and 2 of registration; once appropriate pathology specimens are received, central pathology review will occur within 15 days, and must confirm WHO grade II meningioma before the patient can proceed to step 2 registration and randomization
• PRIOR TO STEP 2 REGISTRATION:
• Histologically confirmed diagnosis of WHO grade II meningioma confirmed by central pathology review prior to step 2 registration
• History/physical examination, including neurologic examination within 60 days prior to step 2 registration
• Post-operative Zubrod performance status 0-1 within 60 days prior to step 2 registration
• If the patient is a woman is of childbearing potential, a serum pregnancy test, obtained within 14 days prior to step 2 registration, must be negative, and, if randomized to receive radiation therapy, the woman must agree to use contraception

Exclusion Criteria:

• Optic nerve sheath meningioma, spinal or other extracranial meningioma, multiple meningiomas, hemangiopericytoma
• Definitive evidence of metastatic meningioma
• Prior invasive malignancy (except non-melanomatous skin cancer) unless disease free for a minimum of 3 years (carcinoma in situ of the breast, oral cavity, cervix, melanoma in situ, or other non-invasive malignancies are permissible)
• Previous radiotherapy to the scalp, cranium, brain, or skull base and radiation-induced meningiomas
• Major medical illnesses or psychiatric impairments, which in the investigators opinion, will prevent administration or completion of the protocol therapy and/or preclude informed consent; these include, but are not restricted to:
  • Unstable angina and/or congestive heart failure requiring hospitalization at the time of step 2 registration
  • Transmural myocardial infarction within the last 6 months prior to step 2 registration
  • Acute bacterial or fungal infection requiring intravenous antibiotics at the time of step 2 registration
  • Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of step 2 registration
  • Type II neurofibromatosis (NF2)
  • Ailments entailing substantial increases in sensitivity and side effect risk from radiation therapy (ataxia telangiectasia, Nijmegen breakage syndrome, and human immunodeficiency virus (HIV) with CD4 count < 200 cells/microliter); HIV testing is not required for eligibility for this protocol, and known HIV positive patients are eligible, provided they are under treatment with highly active antiretroviral therapy (HAART) and have a CD4 count >= 200 cells/microliter within 30 days prior to step 2 registration
  • Inability to undergo MRI with and without contrast (e.g. claustrophobia, non-MRI compatible implant or foreign body, etc) or receive gadolinium; note that patients with severe claustrophobia are permitted on this study if they are willing and able to undergo MRI with adequate sedation or anesthesia
• Pregnancy and/or nursing females