Duration of Anticoagulation for Venous Thromboembolism in Pediatric Patients: Kids-DOTT Trial Outcomes at Two Years

BACKGROUND The Kids-DOTT multinational randomized clinical trial (RCT) revealed non-inferiority of a six-week versus three-month duration of anticoagulation for the treatment of provoked venous thromboembolism (VTE) in patients <21 years old, in regard to net clinical benefit at one year. OBJECTIVE To evaluate non-inferiority at two years. PATIENTS/METHODS Patients whose repeat imaging six weeks after VTE diagnosis did not show complete veno-occlusion were randomized to discontinue anticoagulation versus receive a total three-month course and followed for two years for the occurrence of symptomatic recurrent (SR-) VTE (efficacy outcome) and clinically-relevant bleeding (CRB, safety outcome). Outcomes were centrally adjudicated and net clinical benefit was compared between treatment arms via a pre-specified bivariate non-inferiority boundary, using 95% confidence intervals (CIs) in absolute risk differences (ARDs) between treatment arms. RESULTS Kaplan-Meier estimates of two-year cumulative incidences in the six-week and three-months arms of the intention-to-treat (ITT) population (n=417) were 1.7% (95% CI: 0%, 3.7%) and 2.9% (95% CI: 0.3%, 5.4%) for SR-VTE and 1.1% (95% CI: 0%, 2.5%) and 3.2% (95% CI: 0.6%, 5.7%) for CRB. Bivariate analysis of the ARDs in the ITT population demonstrated that a six-week anticoagulation duration was non-inferior to a three-month course. CONCLUSIONS These findings support durability of the Kids-DOTT RCT findings of net clinical benefit at two years.