Weight Adjusted Low-Dose Warfarin Decreases the Incidence of Thalidomide (T) Associated Venous Thromboembolism (VTE) in Patients (pts) with Multiple Myeloma (MM) and Waldenstroms Macroglobulinemia (WM).

Introduction: T is an effective antimyeloma therapy. An important and problematic side effect of T is development of VTE. The underlying etiology of T associated VTE remains unknown, though a definite rise in its incidence is recorded when combined with other antimyeloma therapies such as dexamethasone (15%) and doxorubicin (26%). Defining an optimal way to prevent T associated VTE is important to improve patient’s quality of life and safety of T. We prospectively investigated the use of weight-adjusted, low-dose warfarin to decrease the incidence of VTE among pts treated with T based regimens.

Methods: All pts treated with T-based therapies, at our institute were given VTE prophylaxis with 1 vs. 2mg warfarin for actual body weight <70 kg vs. ≥ 70 kg, respectively. Concurrent aspirin or other anticoagulants were not given. Pts with underlying pre-existing hypercoaguable disorders were fully anticoagulated with warfarin and were excluded from this analysis. Warfarin was continued throughout the duration of T therapy.

Results: A total of 80 pts, 60 years (range 43–82), 35M and 45F are included in this analysis. Sixty three had stage III and 14 had ≤ stage II MM while 3 pts had WM. T was given with dex in 58 (72%) with dox in 57(71%) and with bortezomib in 32 (40%). Table 1 outlines the T based regimens used. IgG MM was noted in 39, IgA in 20 and 31 had other types of MM. Median T dose was 200 mg (range 50–300) and the median duration 4 months (range 1–6 months). Thirty two pts received 1mg and 48 received 2mg warfarin. Overall incidence of VTE was 6.25% (n=5). There were no bleeding complications noted with the use of warfarin in this pt population.

Conclusion: Our study demonstrates for the first time that a weight adjusted low-dose warfarin approach in MM pts decreases the incidence of T associated VTE and can be safely instituted in pts treated with this important anti-myeloma therapy. Interestingly, none of the pts who received T with Doxil experienced any episode of VTE.