Incidence, Management and Outcomes of Arterial and Venous Thromboembolism after Chimeric Antigen Receptor Modified T Cells for B-Cell Lymphoma and Multiple Myeloma

Introduction: Chimeric antigen receptor modified T Cell (CAR-T) therapy is a rapidly developing treatment for patients with relapsed/refractory (R/R) B-cell non-Hodgkin lymphoma (NHL) or multiple myeloma (MM). Although this population is at high risk for thrombosis, there are few data about rates of venous thromboembolism (VTE) and arterial thromboembolism (ATE) with CAR-T. Additionally, treatment with anticoagulation is complicated because of the prevalence of thrombocytopenia following CAR-T. Our goal was to determine the incidence, associated risk factors, management and outcomes of VTE and ATE in the 60 days following CAR-T therapy.

Methods: We performed a single-center, retrospective cohort study of all patients who received inpatient CAR-T cells at UCSF Medical Center between January 2018 and May 2020 for R/R NHL or MM as standard-of-care or on a clinical trial. The outcomes of incident VTE and ATE were identified by ICD-10 codes and medical record review. Patient characteristics, pre-existing thrombosis risk factors, laboratory results, medications, and major or clinically relevant non-major bleeding or recurrent thrombotic complications were obtained through chart review. We used descriptive statistics to delineate risk factors, incidence, management and outcomes of thrombotic events.

Results: Ninety-one patients who underwent CAR-T therapy were included in the analysis, 37 with NHL and 54 with MM. For NHL, mean age was 63 (range 38-82), and 41% were women. For MM, mean age was 62 (range 33-77), and 50% were women. Patients with NHL were treated with either investigational or Federal Drug Administration-approved CD19-directed therapies, and patients with MM were treated with a variety of investigational B-cell maturation antigen-directed (BCMA) therapies.

For thrombotic risk factors, 13% of patients with NHL had a history of VTE, 3% had a history of ATE, 27% had a BMI ≥30, 59% had a recent procedure including central venous catheter (CVC) placement, 14% had an intensive care unit (ICU) stay, and 22% had an infectious complication in the 30 days pre- or post-CAR-T. Forty-one percent of patients with NHL had neurotoxicity of any grade, and 59% had CRS of any grade. At 30 days, 57% had a complete response, 41% had a partial response, 3% had stable disease. For MM, 6% of patients had a pre-existing history of VTE, 2% had a history of ATE, 19% had a BMI ≥30, 96% had a recent procedure, 11% had an ICU stay and 19% had an infection. Seventeen percent had neurotoxicity, and 85% had CRS. Thirty-two percent of patients with NHL and 48% with MM received pharmacologic VTE prophylaxis while undergoing CAR-T. For those who did not receive VTE prophylaxis, thrombocytopenia was the reason for holding prophylaxis, which occurred in 51% and 50% of NHL and MM patients, respectively.

In the 60 days post-CAR-T, 4 (11%) patients with NHL were diagnosed with VTE—3 pulmonary embolism (PE) and 1 lower extremity deep vein thrombosis (DVT) associated with a previously placed inferior vena cava filter. Four (7%) patients with MM were diagnosed with VTE—1 PE and 3 upper extremity DVTs associated with CVCs. Five out of these 8 (63%) patients had symptomatic VTE, while the remainder were incidental on PETCT. Mean time from CAR-T infusion to VTE diagnosis was 20 days (range 6-39 days). There were no documented ATEs. Six out of 8 (75%) were treated with therapeutic anticoagulation. Of those who were anticoagulated, 4 patients received direct oral anticoagulants and 2 received low-molecular-weight-heparin. Duration was 3 months in 3 patients, 11 days in 1, 150 days in 1, and indefinitely in 1 with atrial fibrillation. Among all 8 patients with VTE, there were no bleeding events or recurrent thromboses regardless of whether or not they received anticoagulation.

Discussion: In this cohort of patients with R/R NHL or MM who received either CD19- or BCMA-directed therapies, almost 1 in 10 developed VTE in the 60 days post-CAR-T. This occurred in the context of a high prevalence of risk factors for thrombosis and low rates of pharmacologic prophylaxis. Among those who developed VTE, the majority were treated with therapeutic anticoagulation for at least 3 months, without documented bleeding or recurrent VTE. Our findings provide crucial information on a common complication that can inform patients, clinicians and researchers and should be expanded upon in larger, prospective studies to identify optimal preventive and therapeutic strategies.