Bleeding and thrombosis in patients receiving chimeric antigen receptor T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapy has transformed the management of relapsed or refractory hematologic malignancies but is accompanied by immune-mediated toxicities that may disrupt hemostatic balance. In addition to cytokine release syndrome (CRS), immune effector cell–associated neurotoxicity syndrome (ICANS), and cytopenias, emerging data suggest an increased incidence of both thrombotic and bleeding complications following CAR T-cell infusion. We conducted a narrative review to evaluate the incidence, timing, risk factors, mechanisms, and management of CAR T-cell–associated coagulopathy, including 5 phase III randomized controlled trials and 11 observational studies published after 2020. Venous thromboembolism (VTE) was the most frequently reported thrombotic event, with rates ranging from 0.48–3.26% in trials and 2.1–10.8% in observational cohorts, typically occurring within the first 30–90 days post-infusion and often overlapping with CRS or ICANS. Arterial events were less common (<2%). Reported bleeding rates were low in trials (0–1.85%) but higher in observational studies (2.8–12.5%), frequently associated with thrombocytopenia, hypofibrinogenemia, and markers of endothelial activation. Anticoagulation for established VTE did not appear to confer excess major bleeding in limited series. Current evidence does not support routine thromboprophylaxis for all CAR T-cell recipients. Instead, thrombotic and hemorrhagic risks appear intertwined and temporally dynamic, driven by inflammation, endothelial injury, and cytopenias. Prospective studies incorporating standardized endpoint adjudication and risk stratification are needed to inform individualized prevention and management strategies.