Patients with unprovoked venous thromboembolism (VTE) or VTE associated with persistent risk factors have a high risk of recurrence after stopping anticoagulation. In the PADIS-PE trial comparing an additional 18 months of warfarin (target international normalized ratio (INR) from 2 to 3) versus placebo in 371 patients who have completed 6 months of anticoagulation for a first unprovoked pulmonary embolism, the PADIS-PE trial confirmed that prolonged warfarin therapy was highly effective for preventing recurrent VTE but that benefit was lost after stopping anticoagulation. In another trial, similar findings had been reported using direct oral anticoagulants (DOAC) at therapeutic dose. These results reinforce international recommendation for indefinite anticoagulation in patients at high risk of recurrent VTE (unprovoked VTE, recurrent VTE or persistent risk factors).~However, prolonged use of warfarin or DOAC at therapeutic dose is associated with a significant risk of bleeding. Consequently, it has been hypothesized that extended anticoagulation at lower dosage might be as effective as and safer than full dose of anticoagulation. However, low-dose warfarin (INR 1.5-2) was less effective and not safer than conventional dose warfarin (INR 2-3).~Low dose of DOAC has the potential to validate this hypothesis. First, DOACs have been shown to be as effective as and safer than warfarin (INR 2-3) during the first 6 months of anticoagulation after an acute VTE. Second, in a first randomized trial comparing full-dose or low-dose apixaban with a placebo during an additional one year of anticoagulation in patients where physicians were uncertain for prolonging anticoagulation (Amplify-extension trial), low-dose apixaban was more effective than placebo without any major concern regarding safety and possibly as effective as and safer than full-dose apixaban; in a second randomized trial comparing full-dose or low-dose rivaroxaban with aspirin, during an additional one year of anticoagulation in patients where physicians were uncertain for prolonging anticoagulation (Einstein-Choice trial), low-dose rivaroxaban was more effective than aspirin without any major concern regarding safety and possibly as effective as and safer than full-dose rivaroxaban. However, these two studies were not designed and powered to demonstrate non-inferiority on efficacy and superiority on safety of a reduced dose of DOAC versus a full dose DOAC and the selected population did not have strong indications for indefinite anticoagulation. Thus, there is currently no evidence to recommend a reduced dose rather than a full dose of DOAC for extended therapy in patients at high risk of recurrent VTE. Consequently, a randomized trial comparing low-dose DOAC with full-dose DOAC therapy in patients at high risk of recurrent VTE is needed and justified.~Main hypothesis:~After VTE at high risk of recurrence initially treated during 6 (-15 days) to 24 (+3 months) uninterrupted months, a reduced dose of DOAC will be non-inferior to a full dose of DOAC in terms of recurrent VTE during extended anticoagulation phase.~Design~The RENOVE trial is designed as an academic, multicenter, open, with blind evaluation (PROBE), randomized, parallel arm, controlled, trial sponsored by the Brest University Hospital Center. Patients meeting the inclusion criteria will be randomized at visit 1 (day 0) and allocated to receive:~either a reduced dose of DOAC (apixaban 2.5 mg twice daily or rivaroaxaban 10 mg once daily) during a mean follow-up period of 24 months (12 to 48 months)~or a full dose of DOAC (Apixaban 5 mg twice daily or Rivaroxaban 20 mg once daily) during a mean follow-up period of 24 months (12 to 48 months).~The study is powered to demonstrate the following hypotheses using a three steps hierarchical analysis:~Primary hypothesis: non-inferiority of a reduced dose of DOAC as compared to a full dose of DOAC on the risk of recurrent VTE;~Secondary hypothesis: in case of the confirmation of the previous hypothesis, superiority of a reduced dose of DOAC on the risk of major or clinically relevant non-major bleeding.~Third hypothesis: in case of the confirmation of the previous hypothesis, superiority of a reduced dose of DOAC on the risk of the composite of recurrent VTE, major bleeding or clinically relevant non major bleeding.~Randomization will be centralized and stratified on:~Center~Type of DOAC~antiplatelet agent taking~At visit 1, patients will have a therapeutic education and they will be instructed to call research team in case of any medical event during the study treatment period. Follow-up visits will be planned at 3, 6, 12 months and every 6 months until study end (i.e.; after the last included patient has achieved 12- month of study treatment period).~All critical events will be adjudicated by an independent adjudication committee blinded from the treatment allocation. A data safety board will be constituted and will meet on a regular basis. Duration of each patient's participation will be on average 24 months (12 months for the last included patient) and a total duration of the study is expected for 48 months.~Objectives:~Main Objective~• To demonstrate that a reduced dose of DOAC is non-inferior to a full dose of DOAC for the risk of recurrent VTE during the during a mean study treatment period of 24 months in patients with VTE that warrants indefinite anticoagulation and who have been initially treated for 6 (-15 days) to 24 (+3 months) uninterrupted months.~Secondary Objectives~• Key secondary objectives: if the main objective is verified, key secondary objectives are to demonstrate the superiority of a reduced dose of DOAC over a full dose of DOAC during a mean study treatment period of 24 months :~on the risk of major or CRNMB and, if confirmed,~on the composite of recurrent VTE, major bleeding or CRNMB.~• Other secondary objectives:~To evaluate the benefit of a reduced dose of DOAC on the risk of major bleeding during a mean study treatment period of 24 months~To evaluate the benefit of a reduced dose of DOAC on the composite outcome of recurrent VTE and major bleeding during a mean study treatment period of 24 months~To determine the impact of a reduced dose of DOAC on deaths of all causes and deaths related to recurrent VTE or major bleeding during a mean study treatment period of 24 months~To evaluate dyspnea and post-thrombotic syndrome (villalta score)(65).~To evaluate compliance treatment using the Morisky auto-questionnaire (66,67)~To analyse the treatment effect on recurrent VTE and major bleeding and CRNM among predefined sub-groups (screening for heterogeneity among predefined strata).~Sample size justification~In this three steps hierarchical trial, the sample size was calculated on the basis of the following three conditional hypotheses:~Primary hypothesis: non inferiority of a reduced dose of DOAC compared to a full dose of DOAC on the risk of recurrent VTE. Based on an expected rate of recurrent VTE of 2%/year (4% during the entire study period (i.e.; mean study treatment period of 24 months)) in each group and a requirement that the study would have 90% power to exclude a hazard ratio of 1.7* for the primary outcome with a reduced dose of DOAC, at a two-sided alpha level of 0.05, 1030 patients need to be included in each treatment group.~Secondary hypothesis: in case of the confirmation of the previous hypothesis, superiority of a reduced dose of DOAC on the risk of major or clinically relevant non major bleeding. Assuming an estimated incidence in the full-dose DOAC group of 10% in the entire study period and a reduction in the relative risk of at least 35%** with a reduced dose of DOAC as compared with a full dose of DOAC, 966 patients in each group for the study would have 80% power to show the superiority of a reduced dose of DOAC over warfarin, at a two-sided alpha level of 0.05.~Third hypothesis: in case of the confirmation of the previous hypothesis, superiority of a reduced dose of DOAC on the risk of the composite of recurrent VTE, major bleeding or clinically relevant non major bleeding. Assuming an estimated incidence in the full-dose DOAC group of 14% and 10% in the reduced-dose DOAC group in the entire study period, 1029 patients in each group for the study would have 80% power to show the superiority of a reduced dose over a full dose of DOAC, at a two-sided alpha level of 0.05.~Taking in account 5% of loss of follow-up, a total of 2200 patients are required in order to be able to confirm these three conditional hypotheses.
Patients with unprovoked venous thromboembolism (VTE) or VTE associated with persistent risk factors have a high risk of recurrence after stopping anticoagulation. In these patients, international guidelines recommend indefinite anticoagulation. However, prolonged use of warfarin or DOAC at therapeutic dose is associated with a significant risk of bleeding. Consequently, it has been hypothesized that extended anticoagulation at lower dosage might be as effective as and safer than full dose of anticoagulation. However, low-dose warfarin (INR 1.5-2) was less effective and not safer than conventional dose warfarin (INR 2-3).~Low dose of DOAC has the potential to validate this hypothesis. In a first randomized trial comparing full-dose or low-dose apixaban with a placebo during an additional one year of anticoagulation in patients where physicians were uncertain for prolonging anticoagulation (Amplify-extension trial), low-dose apixaban was more effective than placebo without any major concern regarding safety and possibly as effective as and safer than full-dose apixaban; in a second randomized trial comparing full-dose or low-dose rivaroxaban with aspirin, during an additional one year of anticoagulation in patients where physicians were uncertain for prolonging anticoagulation (Einstein-Choice trial), low-dose rivaroxaban was more effective than aspirin without any major concern regarding safety and possibly as effective as and safer than full-dose rivaroxaban. However, these two studies were not designed and powered to demonstrate non-inferiority on efficacy and superiority on safety of a reduced dose of DOAC versus a full dose DOAC and the selected population did not have strong indications for indefinite anticoagulation. Thus, there is currently no evidence to recommend a reduced dose rather than a full dose of DOAC for extended therapy in patients at high risk of recurrent VTE. Consequently, a randomized trial comparing low-dose DOAC with full-dose DOAC therapy in patients at high risk of recurrent VTE is needed and justified.~Main hypothesis:~After VTE at high risk of recurrence initially treated during 6 (-15 days) to 24 (+ 3 months) uninterrupted months, a reduced dose of DOAC will be non-inferior to a full dose of DOAC in terms of recurrent VTE during extended anticoagulation phase.