A Study of Dabigatran Etexilate as Primary Treatment of Malignancy Associated Venous Thromboembolism

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Patients with malignancies are at increased risks of venous thromboembolism (VTE). The annual incidence of VTE in cancer patients is 0.5%, which is 5-fold more than the general population . Low molecular weight heparin (LMWH) has been the standard treatment for malignancy-associated VTE. This recomm...

Patients with malignancies are at increased risks of venous thromboembolism (VTE). The annual incidence of VTE in cancer patients is 0.5%, which is 5-fold more than the general population . Low molecular weight heparin (LMWH) has been the standard treatment for malignancy-associated VTE. This recommendation follows the results of the Randomized Comparison of Low-Molecular-Weight Heparin versus Oral Anticoagulant Therapy for the Prevention of Recurrent VenousThromboembolism in Patients with Cancer (CLOT) trial, which showed superiority of Low molecular weight heparin (LMWH) over warfarin in cancer patients with VTE . Low molecular weight heparin (LMWH) has a number of inherent advantages over warfarin. It does not interact with chemotherapeutic agents, and dose titration is not necessary. Furthermore, the risks of both bleeding and breakthrough VTE are also lower with LMWH. However, the requirement of daily subcutaneous injection makes LWMH inconvenient to use. Most patients have difficulties continuing daily injection, partly owing to compliance issues, but also because an emaciated state in some patients makes subcutaneous injection painful. As the life expectancy of solid cancer patients is improved with novel treatment options, the choice of anticoagulation has become a major issue in the management of VTE in this patient population. The main reason underlying the inferior performance of warfarin in oncology patients is difficult dose titration. Drug interaction and hepatic dysfunction are common in patients on chemotherapy. Frequent interruptions of warfarin for invasive procedures and chemotherapy-induced-thrombocytopenia also lead to fluctuations in anticoagulation level. As a result, highs risk of recurrence of VTE and bleeding were observed in cancer patients taking warfarin. Direct-acting oral anticoagulants (DOACs), on the other hand, may be an attractive alternative treatment to LMWH. They are administered at a fixed dose with predictable pharmacokinetics, so that therapeutic monitoring is not required. There is minimal food and drug interaction. They have been shown to be effective in the treatment of VTE in several pivotal randomized controlled trials in comparison with warfarin . However, their role in malignancy associated VTE is yet to be determined, because cancer patients were either excluded or very much underrepresented in these VTE treatment trials. Moreover, the non-inferiority of DOACs in VTE treatment was only demonstrated against warfarin, which is already shown to be suboptimal in oncology patients. A trial directly comparing DOACs with LMWH in malignancy associated VTE is therefore needed. Dabigatran etexilate is an oral thrombin inhibitor. It was shown in the RECOVER study to be effective in treatment of VTE and it has a lower bleeding risk than warfarin. It is not metabolized by cytochrome P450 system and therefore, in contrast to other DOACs, concomitant administration of CYP3A4 inducers or inhibitors is not a concern. We propose this prospective single armed trial to evaluate the efficacy and safety of dabigatran in the treatment of malignancy associated VTE. We will compare the result with our historical control who were treated with LMWH.

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