Population-based study of long-term anticoagulation for treatment and secondary prophylaxis of venous thromboembolism in men with prostate cancer in Sweden.

BACKGROUND: Epidemiological data on anticoagulation for venous thromboembolism (VTE) in prostate cancer are sparse. We aimed to investigate associations between anticoagulation duration and risks of VTE recurrence after treatment cessation and major on-treatment bleeding in men with prostate cancer in Sweden. METHODS: Using nationwide prostate cancer registry and prescribing data, we followed 1413 men with VTE and an outpatient anticoagulant prescription following prostate cancer diagnosis. Men were followed to identify cases of recurrent VTE, and hospitalized major bleeding. We calculated adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) to quantify the association between anticoagulation duration (reference ≤ 3 months) and recurrent VTE using Cox regression. We estimated 1-year cumulative incidences of major bleedings from anticoagulation initiation. RESULTS: The outpatient anticoagulation prescribed was parenteral (64%), direct oral anticoagulant (31%), and vitamin K antagonist (20%). Median duration of anticoagulation was 7 months. Adjusted HRs (95% CI) for off-treatment recurrent pulmonary embolism (PE) were 0.32 (0.09-1.15) for > 3-6 months' duration, 0.21 (0.06-0.69) for > 6-9 months and 0.16 (0.05-0.55) for > 9 months; corresponding HRs for deep vein thrombosis (DVT) were 0.67 (0.27-1.66), 0.80 (0.31-2.07), and 1.19 (0.47-3.02). One-year cumulative incidences of intracranial, gastrointestinal and urogenital bleeding were 0.9%, 1.7%, 3.0% during treatment, and 1.2%, 0.9%, 1.6% after treatment cessation. CONCLUSION: The greatest possible benefit in reducing recurrent VTE risk occurred with > 9 months anticoagulation for PE and > 3-6 months for DVT, but larger studies are needed to confirm this. Risks of major bleeding were low overall.