A Phase III Study of Enoxaparin Versus Low-Dose Warfarin Versus Aspirin as Thromboprophylaxis for Patients with Newly Diagnosed Multiple Myeloma Treated up-Front with Thalidomide-Containing Regimens

Thalidomide-containing regimens are currently being used as standard initial therapy for both younger and elderly pts with multiple myeloma (MM), but are associated with an increased risk of venous thromboembolism (VTE) which necessitates routine thromboprophylaxis. Controversies exist concerning the best thromboprophylactic regimen to be used in these pts. To address this issue, the Italian Myeloma Network GIMEMA designed a phase III sub-study aimed at prospectively investigating the efficacy and safety of low molecular weight heparin (LMWH) or fixed low-dose warfarin (WAR) or low-dose aspirin (ASA) as prophylaxis against VTE in newly diagnosed MM pts who were randomized to receive primary induction therapy with thalidomide-containing regimens in the context of 2 phase III studies conducted by the same group. In one of these studies, pts with ≤65 years of age were randomly assigned to receive Velcade-Thalidomide-Dexamethasone (VTD) or Thalidomide-Dexamethasone (TD) before autologous transplantation. In the other study, Velcade-Melphalan-Prednisone (VMP) was compared with VMP plus thalidomide (VMPT) for elderly patients aged >65 years. The daily dose of Thalidomide was 200 mg in both VTD and TD, and 50 mg in VMPT. Pts randomized to VTD or TD received a total Dexamethasone dose of 320 mg/cycle, while those assigned to VMP or VMPT were given a total Prednisone dose of 240 mg/m²/cycle. By sub-study design, pts treated on VTD or TD or VMPT were randomly assigned to receive thromboprophylaxis with LMWH (Enoxaparin, 40 mg/d) or WAR (1.25 mg/d) or ASA (100 mg/d) for the duration of induction therapy. At the opposite, pts randomized to VMP did not receive any prophylaxis and were used as controls. Sub-study end points included incidence of VTE, acute cardiovascular events, sudden death, bleeding and any other serious adverse events. At the time of the present analysis, 703 pts who received at least 3 cycles of induction therapy were evaluated. Of these pts, 164 treated on VMP were the control group, while the remaining 539 pts (of whom, 209 treated on VTD, 211 on TD and 119 on VMPT) were randomized to receive either LMWH (n=178) or WAR (n=180) or ASA (n=181). Baseline pts characteristics and risk factors for VTE were comparable in all sub-groups. Overall, the risk of VTE was 3.9% with WAR vs 4.5% with LMWH vs 5.5% with ASA (P values not significant for comparisons between different sub-groups), whereas it was 1.8% among the controls. Median times to onset of VTE for pts treated on LMWH or WAR or ASA were 2.66 vs 2.96 vs 2.10 months, respectively. Pts receiving Velcade-containing regimens (VTD or VMPT) had a VTE frequency in the range of approximately 3%, as compared to 5.8% for pts on TD (P value not significant). The rates of cardiovascular events were 0.6% in each of sub-groups including LMWH, WAR and controls, vs 1.1% for pts treated on ASA. No sudden deaths were reported. The incidence of all grades bleeding was 0.6% with LMWH vs 1.1% with WAR vs 3.3% with ASA (P values not significant for comparisons between different sub-groups), while it was 3.7% among the controls. In conclusion, results of the present analysis show that the overall risk of VTE among sub-groups of pts treated with different thalidomide-containing regimens was not superior to that expected during the natural course of MM. No significant relationship was found between the frequency of VTE and thromboprophylactic regimens, induction treatments (e.g. containing or not Velcade) and age of pts (e.g. young vs elderly). In comparison with LMWH and WAR, there was a higher, albeit marginal, risk of VTE and bleeding complications associated with ASA prophylaxis. Finally, a finding not previously well recognized, fixed low-dose WAR was not inferior to LMWH in reducing the risk of VTE among newly diagnosed MM pts receiving thalidomide-containing regimens. For these pts, LMWH, WAR and ASA are likely to be effective thromboprophylactic regimens.