A case report of hemophagocytic lymphohistiocytosis secondary to tislelizumab and bevacizumab combination therapy for renal cell carcinoma.

Background: Recently, the widespread application of immune checkpoint inhibitors (ICIs) in the field of tumor therapy has brought clinical benefits to many patients with advanced disease. Simultaneously, immune-related adverse events (irAEs) have attracted growing attention from the academic community. ICI-related hemophagocytic lymphohistiocytosis (HLH) is a rare irAE with a low incidence but high potential lethality, the pathophysiological mechanism of which is related to the abnormal activation of T cells resulting from the down-regulation of inhibitory signals. Due to the lack of specific clinical manifestations, HLH is prone to misdiagnosis and missed diagnosis, and its treatment strategy is individualized. Case Description: We report the case of a 64-year-old male patient with stage IV renal cell carcinoma (RCC) treated at Hubei Cancer Hospital, China, who developed HLH after combination therapy with tislelizumab and bevacizumab. In this case, HLH was detected early, and appropriate interventions were implemented in a timely manner. Subsequently, the patient's symptoms improved quickly, and short-term follow-up showed no significant tumor progression. As a rapidly progressing and highly lethal disease, the mortality rate of HLH is as high as 50%; thus, timely diagnosis and standardized treatment are crucial. Conclusions: This study reports the first case of HLH induced by the clinically relevant combination of tislelizumab and bevacizumab in RCC, filling the gap in safety data for this first-line regimen.