(P-352) Effectiveness and Safety of Extended Anticoagulation in Patients with Venous Thromboembolism: A Retrospective Cohort Study

Background: Limited real-world evidence exists for effectiveness and safety of extended oral anticoagulation beyond 6 months of initial treatment for patients with venous thromboembolism (VTE).

Objectives: To assess the effectiveness and safety of extended use of apixaban or warfarin beyond 6 months of initial treatment for prevention of recurrent VTE and adverse major bleeding events among patients with VTE.

Methods: A retrospective cohort study using 2013-2019 Truven Commercial and Medicare Supplemental database was conducted in patients aged ≥18 years with a diagnosis of deep vein thrombosis or pulmonary embolism ascertained from inpatient claims. Patients were included if they initiated anticoagulants within 30 days of their first VTE diagnosis, completed 6 months of therapy (≥ 5-month supply), and had extended treatment with either apixaban or warfarin or no extended therapy. Study outcomes including VTE and major bleeding were compared between apixaban, warfarin, and no treatment groups. Follow-up continued until the occurrence of the first event, switch to the comparator, end of study period, or end of enrollment. Multivariable Cox proportional hazards modeling with inverse probability treatment weighting was used to obtain adjusted hazard ratio (aHR) and 95% confidence interval (95%CI).

Results: The study cohort (mean age=60 ±15 years and 50% males) consisted of 4,338 apixaban users, 5,298 warfarin users, and 5,182 untreated patients. The incidence rates of recurrent VTE were 0.22, 0.50, and 1.76 per 100 person-years, and those of major bleeding were 0.62, 1.69, and 0.52 per 100 person-years in the apixaban, warfarin, and no treatment groups, respectively. Compared to no treatment, the use of apixaban was associated with a decreased risk of recurrent VTE (aHR=0.11, 95%CI=0.03-0.25) without increasing the risk of major bleeding (aHR=0.92, 95%CI=0.45-1.91); the use of warfarin was associated with a decreased risk of recurrent VTE (aHR=0.22, 95%CI=0.11-0.43) but with an increased major bleeding risk (aHR=2.53, 95%CI=1.46-4.38). Compared to the use of warfarin, the use of apixaban was associated with a lower risk of major bleeding (aHR=0.39, 95%CI=0.20-0.76) although there was no difference in recurrent VTE risk (aHR=0.45, 95% CI=0.15-1.33).

Conclusions: Extended anticoagulation with apixaban or warfarin was associated with a reduced risk of recurrent VTE among commercially insured patients with VTE. Apixaban had a better safety profile with fewer major bleeding events compared to warfarin. Our findings suggest apixaban as an effective and safer option for extended treatment of VTE when compared to warfarin or no treatment.