OBJECTIVE: To examine and compare the safety and efficacy of extended treatment with dabigatran, apixaban, rivaroxaban and warfarin in patients with unprovoked venous thromboembolism.

METHODS: PubMed and Embase were searched for randomized clinical trials reporting on the use of direct oral anticoagulants (DOACs) and warfarin for the extended treatment of VTE. Meta-analysis was performed on studies reporting similar study design and comparator.

RESULTS: A total of 729 articles were identified and 5 studies covering 6 randomized clinical trials met the eligibility criteria and were included in the study. 5 studies were included in the meta-analysis. Results from the meta-analysis showed that the extended use of DOACs and warfarin significantly decreased the risk of recurrent VTE with 83 % when compared placebo. Warfarin (RR: 0.03, CI: 0.00-0.49) and dabigatran (RR: 0.08, CI: 0.03-0.27) showed the largest relative risk reduction followed by apixaban 2.5mg (RR: 0.19, CI: 0.11-0.33), rivaroxaban (RR:0.19, CI: 0.09-0.40) and apixaban 5mg (RR: 0.20, CI: 0.11-0.34). No significant increased risk of major bleeding was observed with the extended use of any DOACs and warfarin compared to placebo (1.15, CI: 0.40-3.31), but an overall increased risk of non-major clinically relevant bleeding (NMCRB) was observed (RR: 2.12, CI: 1.55-2.90). Apixaban 2.5mg and warfarin was not individually associated with an increased risk of NMCRB. Furthermore, it was found from a study not included in the meta-analysis that dabigatran was non-inferior to VKA for the prevention of recurrent VTE (HR: 1.44, CI: 0.78-2.64, p=0.01 for noninferiority) and decreased the risk of NMCRB compared to VKA (RR: 0.58, CI: 0.43-0.77).

CONCLUSION: Extended treatment with both warfarin and DOACs are effective in preventing recurrent VTE and does not increase the risk of major bleeding, but increases the risk of NMCRB.