Use of Novel oral anticoagulants for treatment of venous thromboembolism (VTE) in patients with malignancy: meta-analysis of randomized controlled trials
Venous thromboembolism (VTE) is a frequent complication of cancers. Patients with cancer have at least a 6 fold increased risk for VTE compared to those without cancer, and the diagnosis of VTE in cancer patient is associated with a 2-4 fold decreased survival during the first year. The mainstays of anticoagulant treatment in cancer patients remain unfractionated heparin, LMWH, and the Vitamin K antagonists (VKAs), with current guideline favoring the use of LMWH. Novel oral anticoagulants (NOAs) that directly inhibit factor Xa and thrombin, including dabigatran, rivaroxaban, and apixaban, represents a milestone in the prevention and treatment of VTE. However, there have been no clinical trials to test the efficacy of NOAs in cancer patients, therefore, use of these agents in cancer population is an extrapolation of published results with general population.
Determine the efficacy of novel oral anticoagulants (thrombin inhibitor; dabigatran, and direct factor Xa inhibitors; rivaroxaban and apixaban) in VTE treatment in patients with cancer.
A systematic review was conducted using MEDLINE and EMBASE up to July 2013. Key words used included venous thromboembolism, pulmonary embolism, deep venous thrombosis, cancer, dabigatran, rivaroxaban, and apixaban. Due to the fact that no randomized controlled trials (RCTs) in cancer population, we combined data that were extracted from major RCTs that include cancer patients and performed a sub-group analysis.
Three randomized controlled trials (RCTs) were reviewed, and a total of 550 patients with cancers were analyzed. NOAs are not inferior to the current standard anticoagulant therapy with enoxaparin followed by an adjusted-dose vitamin K antagonist, to prevent symptomatic recurrent venous thromboembolism. Odd ratio (OR) is 0.988 (95% CI, 0.51-1.94). There is no significant heterogeneity. The major bleeding events were not analyzed due to lack of sub-group data in the trials.
Cancer patients have different hemodynamics and unique features that make the treatment of VTE challenging. These includes: tumor-associated pro-coagulant, venous stasis and endothelial damage from chemotherapy and catheters, an increased risk of anticoagulant-related bleeding, and the complexity of anticoagulant control because of the occurrence of urgent procedures. The development of NOAs provided new modalities to treat VTEs in cancer patients, as it showed that NOAs is non-inferior to the current standard anticoagulant therapy. However, large scale randomized controlled trials specifically targeted cancer patients are needed.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.