Rivaroxaban, a direct oral anticoagulant, is effective against venous thromboembolism (VTE) recurrence without increasing the risk of major bleeding in patients with cancer-associated venous thromboembolism (CAT). However, its clot regression effects are poorly understood. This single-arm, prospective interventional study aimed to investigate the clot regression effects of rivaroxaban in 40 CAT patients, through a contrast-enhanced computed tomography at baseline, 3 weeks, and 3 months of rivaroxaban treatment. The primary endpoint was the clot-regression ratio calculated from the thrombus volumes at 3 weeks and 3 months. Compared with baseline, the total clot volume was significantly reduced at both 3 weeks and 3 months after initiation (p < 0.01). The clot-regression rates were statistically significant with 83.1% (95% confidence interval [CI], 73.8-92.3%) at 3 weeks and 98.7% (95% CI, 97.1-100.2%) at 3 months, with complete resolution in 36.1% and 80.8% of patients at 3 weeks and 3 months, respectively. One patient had recurrent VTE after dose reduction, and seven had non-fatal major bleeding. Therefore, rivaroxaban had a sufficient clot-regression effect against CAT with caution of bleeding complication.
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