OC03 | THROMBOEMBOLIC PREVALENCE IN MULTIPLE MYELOMA BEFORE AND AFTER THE INTRODUCTION OF DIRECT ORAL ANTICOAGULANTS: A LONGITUDINAL COHORT STUDY

A. Ramírez¹, A. Orozco², A. Sánchez³, F. Villalpa¹, S. Burgos², G. Cesarman³, G. Rodríguez¹, D. Vieyra², J. Álvarez⁴, G.M. Flores³, S. González¹, D. Martínez², B. Cabello³, R. Espinoza³, O. Fernández³ | ¹Myeloma-clinic Hematology service, Centro Médico Nacional La Raza, Instituto Mexicano del Seguro Social, México City, México; ²Myeloma-clinic Hematology service, Instituto Nacional de Nutrición Salvador Zubirán, México City, México; ³Myeloma-clinic Hematology service, Instituto Nacional de Cancerologçia, México City, Mexico; ⁴Centro Médico Nacional 20 de Noviembre, México City, Mexico

Thromboembolic events are frequent nonhematologic complications of multiple myeloma (MM). This study aimed to quantify the prevalence of thromboembolic events in Mexican MM patients. We conducted a multicenter retrospective cohort study of patients aged ≥18 years from October 1997 to October 2025. Thromboprophylaxis strategies included none, antiplatelet therapy, or anticoagulation (DOACs, VKA, or LMWH). Patients were stratified in the pre-DOAC and DOAC-access eras. The sample size was calculated, assuming an expected incidence of 10%, a 95% confidence level, and an absolute precision of 3%. The required sample size was 384. Normality was assessed using the Kolmogorov-Smirnov test. Comparison between groups was performed using Student's t-test. The association between categorical variables was tested with the x₂ test. Time-to-event analyses were conducted using Kaplan-Meier curves and the log-rank test. Multivariable analyses include logistic regression and Cox proportional hazard models. A total of 517 patients were included. Men accounted for 53.6% and women for 46.4%, with a mean diagnosis age of 55.8 years. Renal involvement was present in 26.9%, and bone disease in 49%. Elevated DHL was observed in 14.9%, and 33.7% underwent autologous stem cell transplantation. The IMPEDE-VTE score median was 6.71 (5-9, RIC 4). Baseline characteristics were similar between groups with and without thrombotic events. According to IMPEDE-VTE, 13% were low risk, 29.4% intermediate risk, and 56.75% high risk. 84.7% received thromboprophylaxis, mainly aspirin (42.6%), DOACs (31%), and vitamin K antagonists (9.9%). Major bleeding occurred in 0.4%. Thromboembolic prevalence was 8.3%. The mean time to thrombosis for the entire cohort was 4.6 months (95% CI 2.3-6.9). Patients' diagnoses in the pre-DOAC access era had a thrombotic incidence of 10.9% (n=35/322), compared with 4.1% (8/195) in the DOAC access era (p=0.007). Kaplan-Meier analysis in the pre-DOAC group showed a median time to thrombosis of 5.8 mo (95% CI 0.6-19.9) vs. 1 mo. (95% CI 0.0-4.1) in the DOAC era (p=0.012). Cox regression did not identify independent predictors of thrombosis. Logistic regression demonstrated a significantly lower odds of thrombosis with anticoagulation compared with antiplatelet therapy (p<0.001). In conclusion, the prevalence of thrombosis in this cohort was 8.3%. Expanded access to DOACs reduced thrombotic events, and the shorter time to thrombosis reflects a shorter follow-up, not increased risk.