This research study is studying a drug as a possible treatment for High Grade Meningioma.

Meningioma is one of the most common primary intracranial tumors, accounting for 13% to 26% of all intracranial tumors. Although most meningiomas are benign tumors and can be cured by surgical resection, more than 20% of WHO II (atypical) and about 3% of WHO III meningiomas are more likely to have local recurrence after initial treatment , And the lifetime is poor. The immunotherapy represented by PD-1 has achieved remarkable efficacy in the treatment of solid tumors, but the application of PD-1 in recurrent meningioma is rarely reported. The study found that the expression of PD-L1 mRNA and protein in high-grade meningioma cells increased, and the total number of T cells, including CD4+ and CD8+ cells, was significantly reduced, suggesting an inhibitory tumor immune microenvironment. Recent studies have shown that giving patients anti-PD-1 antibody immunotherapy prior to conventional treatment can improve the pathological response, enable the body to produce an enhanced and sustained anti-tumor immune response, and form a tumor microenvironment conducive to immunotherapy. Therefore, giving PD-1 antibody before surgery is a new idea for the treatment of meningiomas. This project aims to investigate whether patients with recurrent meningioma will change their immune function and prolong survival after preoperative PD-1 antibody treatment. It is planned to use flow cytometry, multiple immunofluorescence histochemistry technology, T cell receptor sequencing, etc to detect the changes in the patient's immune function before and after treatment, observe the pathological remission rate of PD-1 monoclonal antibody neoadjuvant treatment of recurrent meningioma, and identify potential response biomarkers, and conduct in-depth discussions on this treatment plan to further determine the treatment mode Clinical value and specific mechanism of action in order to improve the clinical treatment level of patients with recurrent meningioma.

Inclusion Criteria:

• Pathologically diagnosed as a patient with WHO grade III recurrent meningioma
• Age ≥ 18 years
• Kps≥70
• able to accept second surgery
• ECOG Performance Status < 2
• Glucocorticoid dosage dexamethasone ≤5mg/ day or equivalent dose

Exclusion Criteria:

• Participants who have had chemotherapy, targeted small molecule therapy or study therapy within 14 days of protocol treatment, or those who have not recovered (i.e., ≤ Grade 1 or at baseline) from adverse events due to agents administered more than 2 weeks earlier.
• Participants who are receiving any other investigational agents.
• Participants who have a diagnosis of an immunodeficiency.
• Requires treatment with high dose systemic corticosteroids defined as dexamethasone >2mg/day or bioequivalent within 7 days of initiating therapy.
• Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent. Unable to undergo brain MRI.