Enoxaparin Thromboprophylaxis in Cancer Patients With Elevated Tissue Factor Bearing Microparticles

The study was a randomized phase II trial to evaluate the cumulative incidence of VTE in cancer outpatients. At baseline, measurement of tissue factor-bearing microparticles (TFMP) was performed by impedance-based flow cytometry based on established methods. (Zwicker et al, 2009) Patients were classified as having high or low TFMP levels based on a reference repository of plasmas from sixty cancer patients. The top tercile of tissue factor-bearing microparticle concentrations from the reference specimens (3.5 x 104 microparticles/µl) was considered a cutoff for "high" and corresponds with previously described "detectable" levels. Patients with high levels were randomized (2:1) to enoxaparin 40 mg subcutaneously once daily or observation. Randomization was stratified based on cancer diagnosis. Low TFMP patients were observed without anticoagulation. Both the treating physicians and patients were blinded to microparticle status in the observation arms.