Risk of Cancer Comparing Warfarin and Direct Oral Anticoagulants: Population-Based Cohort Studies in England and Hong Kong

Previous evidence suggests a potential protective effect of warfarin against cancer, compared to non-users. However, it may be prone to immortal time bias and residual confounding. We aimed to examine the association between cancer and warfarin, compared with active comparator (direct oral anticoagulants). We conducted studies using population-based databases from England and Hong Kong to investigate the association between warfarin and hazard of cancer using a new-user active-comparator cohort design. People with atrial fibrillation aged ≥ 18 years who had first received anticoagulant treatment during 01/01/2011–31/12/2019 were involved. No evidence supported the association between warfarin and hazard of overall cancer, compared with direct oral anticoagulants in both settings (England: hazard ratio [HR] = 1.03, 95