Antithrombotic utilization, adverse events, and associations with treatment outcomes in multiple myeloma: pooled analysis of three clinical trials

Background: Patients with multiple myeloma (MM) are at risk of venous thromboembolism (VTE), worsened by immunomodulatory drugs. Although antithrombotics are recommended for prophylaxis, existing guidelines are suboptimal and treatment outcomes remain unclear. Objectives: This study aimed to investigate adverse events, antithrombotic utilization, and their associations with survival outcomes in patients with MM initiating multi-drug immunomodulatory combinations. Design: A posthoc analysis of individual-participant level data (IPD). Methods: IPD from three daratumumab clinical trials (MAIA, POLLUX, and CASTOR) were pooled. Adverse events incidence and antithrombotic utilization were assessed. Logistic and Cox regression were utilized to examine associations between antithrombotics use with adverse events and survival outcomes at the baseline and 6-month landmark. Results: Among 1804 patients, VTE occurred in 10%, bleeding in 14%, ischemic heart disease in 4%, and stroke in 2%. Patients with these adverse events demonstrated elevated rates of any grade ⩾3 events. Antiplatelet (primarily aspirin) and anticoagulant (primarily LMWH and direct oral anticoagulants) prescriptions have seen an increase from baseline (25% and 14%, respectively) to 6 months (35% and 31%). The primary indication for their use was prophylaxis. Anticoagulant use within 6 months was associated with reduced VTE (OR (95% CI) = 0.45 (0.26–0.77), p = 0.004), while antiplatelet use showed no associations with any evaluated adverse events. Antithrombotics and survival outcomes had no significant associations. Conclusion: This study underscores the complexities of antithrombotic therapy and adverse events in MM and highlights the need for vigilant and proactive management due to increased grade ⩾3 adverse events. While anticoagulant use was associated with reduced VTE risk, further research is needed to optimize thromboprophylaxis guidelines and explore antithrombotic efficacy and safety in patients with MM. Trial registration: MAIA (NCT02252172), POLLUX (NCT02076009), CASTOR (NCT02136134).