Epcoritamab-Induced fatal pleural effusion in diffuse large B-Cell lymphoma: a case report and literature review.

Epcoritamab, a bispecific T-cell engager (BiTE) antibody targeting CD3 and CD20, has shown significant efficacy in treating refractory diffuse large B-cell lymphoma (DLBCL). However, its use can lead to severe side effects, such as tumor flare. Here, we report the case of an 84-year-old male with relapsed DLBCL who developed fatal unilateral pleural effusion following Epcoritamab treatment. Initially, the patient showed a favorable response, but later developed significant pleural effusion with elevated interleukin-6 (IL-6) levels, indicating a severe inflammatory response. This suggests that Epcoritamab directly affected the pleural lesions and caused a local cytokine release syndrome (L-CRS). Despite aggressive management, including Tocilizumab and Dexamethasone, the patient's condition worsened, leading to his death. This case underscores the importance of regular lab tests and imaging follow-ups to monitor and manage severe inflammatory reactions based on tumor location. Comprehensive monitoring protocols are needed to mitigate risks associated with novel immunotherapies. To our knowledge, this is the first reported case of fatal unilateral pleural effusion in a patient with relapsed DLBCL following Epcoritamab treatment.