Young AM, et al. - Researchers tested the efficacy of rivaroxaban (an oral factor Xa inhibitor) as an alternative treatment for venous thromboembolism (VTE) in patients with cancer. Despite a relatively low VTE recurrence, clinically relevant nonmajor bleeding was higher with rivaroxaban vs dalteparin.

Methods

• Researchers performed this multicenter, randomized, open-label, pilot trial in the UK, including patients with active cancer who had symptomatic pulmonary embolism (PE), incidental PE, or symptomatic lower-extremity proximal deep vein thrombosis (DVT).
• They assigned study participants to receive dalteparin (200 IU/kg daily during month 1, then 150 IU/kg daily for months 2-6) or rivaroxaban (15 mg twice daily for 3 weeks, then 20 mg once daily for a total of 6 months).
• VTE recurrence over 6 months was the primary outcome.
• Evaluation of safety was based on rates of major bleeding and clinically relevant nonmajor bleeding (CRNMB).
• A sample size of 400 patients would provide estimates of VTE recurrence to within ± 4.5%, assuming a VTE recurrence rate at 6 months of 10%.

Results

• A total of 203 patients were randomly assigned to each group, 58% of whom had metastases.
• Recurrent VTE was detected in 26 patients (dalteparin, n=18; rivaroxaban, n= 8).
• With dalteparin vs rivaroxaban, the reported 6-month cumulative VTE recurrence rate was 11% (95% CI, 7% to 16%) vs 4% (95% CI, 2% to 9%), respectively (hazard ratio [HR], 0.43; 95% CI, 0.19 to 0.99).
• For dalteparin and for rivaroxaban, the estimated 6-month cumulative rate of major bleeding was 4% (95% CI, 2% to 8%) and 6% (95% CI, 3% to 11%), respectively (HR, 1.83; 95% CI, 0.68 to 4.96).
• For dalteparin and for rivaroxaban, corresponding rates of CRNMB were 4% (95% CI, 2% to 9%) and 13% (95% CI, 9% to 19%), respectively (HR, 3.76; 95% CI, 1.63 to 8.69).