Superficial vein thrombosis treated for 45 days with rivaroxaban versus fondaparinux: rationale and design of the SURPRISE trial

Patients with superficial vein thrombosis (SVT) are commonly treated with low-molecular weight heparin or fondaparinux in prophylactic, intermediate or therapeutic dosages for treatment periods of 10-45 days. This practice is also reflected by the current guideline recommendations. However, given the broad range of thromboembolic complication rates in SVT (between 0 and 30 % have been reported) it seems reasonable to suspect that risk stratification is needed to differentiate patients at low risk who may not benefit from anticoagulation from those at high risk who may need higher dosages or a longer duration of anticoagulation. Furthermore, prolonged treatment with injectable anticoagulants has been shown to result in poor patient adherence. Direct oral anticoagulants have recently been approved for venous thromboembolism therapy and these new drugs may offer advantages also for SVT patients. The prospective, randomized, open-label, blinded adjudication trial superficial phlebitis treated for 45 days with rivaroxaban versus fondaparinux (SURPRISE) will evaluate the efficacy and safety of 10 mg rivaroxaban OD compared to fondaparinux 2.5 mg OD for SVT treatment in a subset of high-risk SVT patients over a treatment period of 45 days. The purpose of the study is to demonstrate non-inferiority of rivaroxaban compared to fondaparinux in preventing the combined efficacy endpoint of thrombus progression, SVT recurrence, DVT, PE and death. The results of the SURPRISE trial will provide evidence for the concept of risk stratification in SVT and for the value of rivaroxaban 10 mg in SVT treatment (clinicaltrials.gov NCT01499953).