Incidence and Outcomes of Brain Metastasis in Pleural Mesothelioma in the Era of Immunotherapy.

INTRODUCTION

Immunotherapy (IO) has reported efficacy in pleural mesothelioma (PM). Brain metastases (BMs) in PM are rare; thus, surveillance brain imaging is not included in the guidelines. We evaluated the incidence of BM by treatment type.

METHODS

In this retrospective analysis, patients with PM treated at the University of Pennsylvania between January 1, 2015, and August 31, 2023, were included. Demographic and clinical data were extracted from the medical records. The treatment categories included chemotherapy, single-agent IO, and dual-agent IO. A two-tailed Z score was used to determine a difference in the proportion of BM. Overall survival (OS) was analyzed using the Kaplan-Meier method. Of those with BM, available brain tissue was further analyzed.

RESULTS

In total, 251 patients were included; the median age of the participants was 73 years (range: 35-92 y), 79% were male individuals, 91% were white, and 73% had epithelioid histology. In the study, 102 (40.6%) were treated with chemotherapy, 100 (39.8%) with single-agent IO, and 49 (19.5%) with dual-agent IO. The median OS (mOS) was 21.6 months (95% confidence interval: 17.7-25.5) and did not differ between treatment groups (p = 0.774). A higher proportion of patients treated with IO developed BM than those treated with chemotherapy (6/149 [4%] versus 0/102 [0%]; Z score p = 0.04). The mOS from BM diagnosis was 95 days (range: 16-1025 d). The histomorphology of three patients with available brain tissue were similar to the primary site and reported substantial edema and hemorrhage.

CONCLUSIONS

In this retrospective study, clinically significant BM was most prevalent in those exposed to IO and not seen in those receiving chemotherapy despite similar mOS between the groups. Brain imaging should be considered before starting IO in patients with PM.