OC 32.1 - Risk of CAR T-cell therapy-related thrombosis and bleeding: preliminary results of the multicenter ‘Follow that CAR’ registry

Background: Chimeric antigen receptor T-cell (CAR-T) therapy has dramatically changed treatment and survival rates for patients with hematological malignancies. Reports on thrombosis and bleeding complications after CAR-T are emerging, but their relevance remains unclear because of large heterogeneity between studies.

Aims: To assess incidence of thrombosis and bleeding in a homogenous cohort of adults with lymphoma undergoing CAR-T therapy, and evaluate anticoagulation use in this population.

Methods: We used the ‘Follow that CAR’ registry, a retrospective multicenter cohort including adults with relapsed/refractory lymphoma receiving CAR-T therapy in the Netherlands between 2020-2022. Patients were monitored from start of lymphodepleting chemotherapy before CAR-T until 1 year after infusion. We recorded all venous and arterial thrombosis, major bleeding (according to ISTH definition) and death events during follow-up.

Results: 58 patients treated in Erasmus MC were included in this analysis (baseline characteristics; Table 1). After median follow-up of 372 days, 5 patients experienced thrombosis (incidence rate 11.6% [95% CI, 3.76-27.02] per person-year); 3 had venous (all in upper extremity after central venous catheters) and 2 arterial thrombosis (1 myocardial infarction, 1 peripheral artery disease-related limb event). 4 patients experienced major bleeding (incidence rate 8.7% [95% CI, 2.38-22.37] per person-year). Median time to thrombosis and major bleeding was 55 and 22.5 days, respectively. 17 patients (29.3%) received thromboprophylaxis during CAR-T infusion, 12 (20.7%) therapeutic anticoagulation. One patient received therapeutic anticoagulation at time of major bleeding, all other thrombosis or bleeding occurred in patients without prophylactic or therapeutic anticoagulation. 17 (29.3%) patients had died after 1 year follow-up, mostly due to progression of underlying disease.

Conclusion(s): This homogeneous cohort confirms that patients are at considerable risk of thrombosis and bleeding in the first year after CAR-T therapy. These preliminary results will be completed with data from other Dutch centers, but justify further research on the relevance and prevention of these complications.