Prevention of venous thromboembolism in acutely ill medical patients after the results of recent trials with the new oral anticoagulants

Has time come for the use of direct oral anticoagulants in the extended prophylaxis of venous thromboembolism in acutely ill medical patients? Yes

Betrixaban is a direct factor Xa inhibitor with a renal excretion of only approximately 5-7%. On June 23rd 2017, it became the first direct oral anticoagulant to receive Food and Drug Administration approval for the prevention of venous thromboembolism in acutely ill medical patients, and the first anticoagulant agent to be approved for extended-duration thromboprophylaxis after hospital discharge in this setting. Approval followed the results of the APEX trial, a phase III clinical trial comparing betrixaban (80 mg) administered for 35-42 days with enoxaparin (40 mg) administered for 10 ± 4 days. This study for the first time applied a risk assessment model, integrating clinical factors and a laboratory marker to identify high risk patients. To improve safety, a dose reduction was used for patients with creatinine clearance between 15 and 30 mL/min (betrixaban 40 mg and enoxaparin 20 mg) and for patients receiving concomitant treatment with potent P-glycoprotein inhibitors (betrixaban 40 mg). The primary prespecified analysis tested the hypothesis that the benefit of extended thromboprophylaxis with betrixaban was greatest in patients with elevated D-dimer, but the 21% relative risk reduction failed to meet the prespecified threshold for statistical significance. However, the analysis of the overall study population showed a favorable net clinical benefit with betrixaban, with a statistically significant reduction in all efficacy outcomes and no increase in major bleeding rates. An ongoing trial, MARINER, is also assessing a combined approach for risk stratification comparing extended-duration rivaroxaban with standard duration low molecular weight heparin.

Efficacy and safety of extended thromboprophylaxis for medically ill patients. A meta-analysis of randomised controlled trials

Compelling evidence suggests that the risk of pulmonary embolism (PE) and deep-vein thrombosis (DVT) persists after hospital discharge in acutely-ill medical patients. However, no studies consistently supported the routine use of extended-duration thromboprophylaxis (ET) in this setting. We performed a meta-analysis to assess efficacy and safety of ET in acutely-ill medical patients. Efficacy outcome was defined by the prevention of symptomatic DVT, PE, venous thromboembolism (VTE) and VTE-related mortality. Safety outcome was the occurrence of major bleeding (MB) and fatal bleeding (FB). Pooled odds ratios (ORs) and 95 % confidence intervals (95 %CI) were calculated for each outcome using a random effects model. Four RCTs for a total of 28,105 acutely-ill medical patients were included. ET was associated with a significantly lower risk of DVT (0.3 % vs 0.6 %, OR 0.504, 95 %CI: 0.287-0.885) and VTE (0.5 % vs 1.0 %, OR: 0.544, 95 %CI: 0.297-0.997); a non-significantly lower risk of PE (0.3 % vs 0.4 %, OR 0.633, 95 %CI: 0.388-1.034) and of VTE-related mortality (0.2 % vs 0.3 %, OR 0.687, 95 %CI: 0.445-1.059) and with a significantly higher risk of MB (0.8 % vs 0.4 %, OR 2.095, 95 %CI: 1.333-3.295). No difference in FB was found (0.06 % vs 0.03 %, OR 1.79, 95 %CI: 0.384-8.325). The risk benefit analysis showed that the NNT for DVT was 339, for VTE was 239, and the NNH for MB was 247. Results of our meta-analyses focused on clinical important outcomes did not support a general use of antithrombotic prophylaxis beyond the period of hospitalization in acutely-ill medical patients.

Primary prophylaxis of VTE in cancer outpatients

Cancer patients have a significantly higher risk of developing venous thromboembolism (VTE) compared to non-cancer patients and several studies suggest that VTE risk among ambulatory cancer patients varies widely. Recently, predictive models capable of risk-stratifying a broad range of ambulatory cancer outpatients have been developed and validated; using the Khorana model a score of 2 is associated with an intermediate-high risk for VTE. However, the use of VTE prophylaxis in ambulatory patients who have cancer remains controversial. Even if important randomized clinical trials showed decreased rates of VTE events among patients who were receiving chemotherapy, the effect of prophylaxis on morbidity, mortality, and costs has not been rigorously studied. Outpatients with active cancer should be assessed for thrombosis risk and although most do not routinely require thromboprophylaxis, it should be considered for high risk patients.