DP058 | THROMBOTIC AND BLEEDING EVENTS AFTER CD19 CAR-T THERAPY IN LBCL: REAL-WORLD EVIDENCE FROM 381 PATIENTS

Occurrence of thrombotic events following CAR-T therapy remains poorly characterized, with limited data on their incidence, timing, and risk factors. In this study, we analyzed 381 consecutive patients with large B-cell lymphoma treated with CD19 CAR-T cells at two hub centers (Rome and Paris) between 2019 and 2024. Primary endpoints were thrombotic events and bleeding episodes occurring within 12 months post-CAR-T infusion. Patients were censored at lymphoma relapse. Clinical and laboratory risk factors were evaluated. Overall, thrombotic events occurred in 22 patients (5.8%) and the median onset of those episodes was 9 days post-infusion (range 2–340). Of these, 18 were deep vein thromboses (including 6 pulmonary embolisms), and 4 were arterial events (all ischemic strokes). Patients with thrombosis had higher peak activated partial thromboplastin time during the acute phase (median 46 vs. 40 seconds, p<0.001). Although univariate analysis showed trends for increased thrombosis in patients with elevated CAR-HEMATOTOX, clinical ICANS, or steroid use, only ICU admission remained an independent risk factor in multivariate analysis (HR 4.9, 95% CI 1.84–13.19). Thrombotic risk was not associated with traditional cardiovascular risk factors, age, sex, ECOG performance status, CAR-T product (axi-cel vs. tisa-cel), disease status at infusion, baseline mEASIX, or prior thrombotic events (<6 months). Bleeding events were observed in 13 patients (3.4%) at a median of 12 days post-infusion (range 1–270), mostly classified as minor. Univariate analysis linked early bleeding with antiplatelet therapy, ICANS, steroid use, and platelet nadir <20×10⁹/L. However, only ICANS remained an independent predictor in multivariate analysis (HR 7.3, 95% CI 1.63–32.22). In conclusion, while bleeding events after CAR-T are infrequent and generally mild, thrombosis unrelated to lymphoma relapse occurs in 5.8% of patients within the first year, primarily associated with ICU admission during acute toxicity. Pulmonary embolism and ischemic stroke accounted for half of all events, highlighting the need for careful consideration of thromboprophylaxis in the early post-infusion period.