Rationale and Design of the DEFIANCE Study: A Randomized Controlled Trial of Mechanical Thrombectomy Versus Anticoagulation Alone for Iliofemoral Deep Vein Thrombosis

Background: Deep vein thrombosis (DVT) is a common medical condition that is associated with clinically significant sequelae, including postthrombotic syndrome (PTS). Anticoagulation alone remains the guideline-recommended treatment for many patients with iliofemoral DVT. Recent technological advances have led to an increase in the use of mechanical thrombectomy for DVT, but mechanical thrombectomy-based procedures have not yet been compared with standard-of-care anticoagulation therapy in randomized studies.

Methods: The DEFIANCE study (ClinicalTrials.gov: NCT05701917) is an international and actively enrolling randomized controlled trial (RCT) in lower extremity DVT assessing an interventional strategy that includes mechanical thrombectomy with the ClotTriever System (Inari Medical, Irvine, CA) versus anticoagulation alone. Approximately 300 patients with unilateral iliofemoral DVT and symptom duration ≤12 weeks will be randomized 1:1. Study conduct includes an independent core laboratory for duplex ultrasound assessment, an independent medical monitor for safety adjudication, and evaluation of PTS severity on the Villalta scale using best clinical practices. The primary endpoint is a composite outcome structured as a hierarchal win ratio of 1) the occurrence of treatment failure or therapy escalation as adjudicated by the medical monitor, with failure defined as amputation or gangrene of the target leg or venous thromboembolism-related mortality, and 2) the assessment of PTS severity at the 6-month follow-up visit. In addition to being a component of the primary endpoint, the severity of PTS at 6 months is also evaluated as a stand-alone secondary endpoint. An additional secondary endpoint is a composite of outcomes at the 10-day visit and is structured as a hierarchal win ratio of 1) vessel compressibility on duplex ultrasound, 2) patient-reported pain, and 3) improvement of edema. The safety endpoints are access site complications requiring endovascular or surgical repair and the occurrence through the 30-day visit of mortality, major bleeding, or new symptomatic pulmonary embolism.

Conclusions: DEFIANCE will be the first RCT to evaluate a mechanical thrombectomy-based interventional approach versus anticoagulation therapy alone for DVT. The results will inform the treatment of patients with iliofemoral DVT and the prevention of PTS-associated morbidity.

Trial registration: DEFIANCE: RCT of ClotTriever System Versus Anticoagulation In Deep Vein Thrombosis (DEFIANCE), ClinicalTrials.gov: NCT05701917, URL: https://clinicaltrials.gov/study/NCT05701917?cond=Deep%20Vein%20Thrombosis&term=defiance&rank=1.