An Open-Label Phase II Study of Nivolumab or Nivolumab/Ipilimumab in Adult Participants With Progessive/ Recurrent Meningioma

Inclusion Criteria: * Have histologically confirmed WHO grade I, II or III meningioma that is progressive or recurrent. Metastatic meningiomas are allowed. Participants with grade I tumors must have failed radiation therapy. * Prior therapy: * There is no limit on the number of prior surgeries, radiation therapy, radiosurgery treatments or systemically administered therapeutic agents. * Patients may have been treated with standard external beam radiation or radiosurgery in any combination, however, an interval of ≥ 12 weeks (84 days) must have elapsed from the completion of the radiation therapy to start of study therapy unless there is histopathologic confirmation of recurrent tumor or there is new enhancing tumor outside the radiation field (beyond the high dose region or the 80% isodose line). * In addition, there must be subsequent evidence of tumor progression after completion of radiation therapy (grade I tumors only) * An interval of ≥ 28 days and full recovery (no ongoing safety issues) from surgical resection * An interval of ≥ 7 days from stereotactic biopsy; * For prior systemic agents, participants must be at least 4 weeks (or 5 half-lives, whichever is shorter) from other prior cytotoxic chemotherapy (6 weeks from nitrosoureas) or biologic therapies. * Participants must have recovered to grade ≤ 1 or pretreatment baseline from clinically significant adverse events related to prior therapy (exclusions include but are not limited to alopecia, laboratory v…