# Case Report: Advanced grade 2 meningioma with PBRM1 inactivation with prolonged response to immunotherapy

## TL;DR

A grade 2 meningioma with PBRM1 inactivation showed a long-lasting response to pembrolizumab immunotherapy.

## Contribution

This case report adds new evidence on the potential of immunotherapy in PBRM1-mutated meningiomas.

## Key findings

- The tumor showed functional loss of PBRM1 and BAP1 with a tumor mutational burden of 4 Muts/Mb.
- Prolonged response to pembrolizumab was observed despite a low PD-L1 tumor proportion score.
- The case contributes to the limited literature on PBRM1 mutations in meningiomas and immunotherapy response.

## Abstract

Meningiomas are the most common primary tumor in the central nervous system, yet an effective systemic treatment remains a challenge. We present a grade 2 meningioma that resulted in a positive and prolonged response to pembrolizumab. Our case had polybromo-1 (PBRM1) and BAP1 functional loss, tumor mutational burden of 4 Muts/Mb, stable microsatellite status, and a PD-L1 tumor proportion score of <1%. We add to the limited literature regarding PBRM1 mutations in meningiomas. We discuss our findings in relation to the ongoing investigation of immune checkpoint inhibitor therapy in treating higher-grade refractory meningiomas.