Abstract
Immune checkpoint inhibitors (ICIs) have improved the clinical outcome of NSCLC. However, immune-related adverse events (irAEs) such as pneumonitis, thyroiditis, and colitis have been reported with the increasing use of ICIs. The diagnosis of irAEs relies on exclusion. With proper management, most patients may still benefit from ICI treatment. Pleural effusion is a rare presentation of an irAE. Here, we report a patient who experienced progressive bilateral pleural effusions during the first-line treatment of cisplatin, pemetrexed, and pembrolizumab. Serial study and surgical pleural biopsy found the possible cause of irAE. His pleural effusion subsided after discontinuing therapy. IrAE may present as pleural effusion and physicians should be alert to unknown causes of pleural effusion in patients under ICI treatment.