Bleeding and thrombotic events occur within the first 3 months after chimeric antigen receptor (CAR) T-cell therapy, and some patients are at higher risk of bleeding, according to research published in Blood Advances.

In this study, the authors evaluated the incidence of bleeding and thrombotic events in adults with diffuse large B-cell lymphoma (DLBCL) or B-cell acute lymphoblastic leukemia (B-ALL).

A total of 9.4% of patients developed bleeding and 6.3% developed thrombotic complications within the first 3 months after receiving CAR-T infusion. All bleeding events occurred within the first month after CAR-T therapy.

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The study included 127 patients receiving CD19-directed CAR-T therapy. There were 12 patients who had study-defined bleeding and 8 patients who had thrombotic complications.

Thrombotic complications included deep vein thrombosis, thrombotic stroke, and splanchnic vein thrombosis. Bleeding events included gross hematuria, soft tissue bleeding, subdural hematoma, gastrointestinal hemorrhage, and hemoptysis.

Patients who had a low baseline platelet count and high-grade immune-effector cell-associated neurotoxicity syndrome (ICANS) had the highest risk of bleeding events. This suggests these patients may need monitoring after therapy.

More than half of bleeding events within the first 30 days after CAR-T therapy occurred after the patient was discharged, signaling a need to follow up with these patients.

“Our findings suggest that a systemic coagulopathy occurs after CAR T therapy, coinciding with predominant bleeding manifestations,” the authors wrote in their report. “However, despite a high incidence of DIC [diffuse intravascular coagulation] according to standard criteria this itself does not appear to modulate the risk of bleeding in our study. This finding raises questions about the generalizability of routinely used scoring algorithms for DIC in CAR-T settings and may imply that biologic processes mediating CAR T-related coagulopathy are more distinct from other known disorders associated with DIC.”

This study was limited by its small sample size and retrospective design. The study detected a trend toward increased risk of bleeding and thrombotic events based on age or history of thrombosis, but these weren’t significant. The study size may have also been underpowered for this analysis.

Further prospective studies should examine the risk factors for bleeding and thrombotic complications.

Disclosure: One or more study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Johnsrud A, Craig J, Baird J, et al. Incidence and risk factors associated with bleeding and thrombosis following chimeric antigen receptor T-cell therapy. Blood Adv. 2021;5(21):4465-4475. doi:10.1182/bloodadvances.2021004716