Effectiveness and Safety of Lower Dose of Rivaroxaban for Cancer-Related Venous Thromboembolism: A Retrospective Cohort Study

Background: Primary and recurrent venous thromboembolism (VTE) commonly occur in patients with cancer. However, because of the National Health Insurance regulations, available dosage forms, and clinical conditions, the prescribed dose of rivaroxaban may not be consistent with its recommended dose. Objective: To evaluate the 6-month recurrence rate of VTE and safety of rivaroxaban for patients with cancer. Methods: Patients with new cancer diagnosis or recurrence from 2014 to 2018 who initiated rivaroxaban for VTE from January 2015 to January 2019 were included. We set the rivaroxaban initiation date as the index date and followed up the patients for 180 days. We collected information regarding the starting and maintenance dose/frequency and the treatment duration. The efficacy outcome was the recurrence of VTE within 180 days. The safety outcome included the major bleeding rate and clinically relevant nonmajor bleeding (CRNMB) rate. Results: Approximately, 46.2% of the 65 included patients received a standard starting dose, and 45% of patients received a maintenance dose above 15 mg (median: 23.9 and 13.1 mg per day, respectively). Two-thirds of the patients stopped treatment within 180 days. Recurrent VTE occurred in 2 (3.1%) patients within 6 months. The major bleeding rate was 7.7%, and the CRNMB rate was 3.1%. Conclusion and Relevance: The 6-month recurrence rate of VTE and safety profile were similar between the lower and standard dose of rivaroxaban. This result may be applied to the institutions with dosage availability limited by formulary regulation and patients who cannot use full dose because of clinical considerations.