The effect of warfarin therapy on breast, colorectal, lung, and prostate cancer survival: a population-based cohort study using the Clinical Practice Research Datalink

Abstract

Purpose: Pre-clinical studies suggest that oral anticoagulant agents, such as warfarin, may inhibit metastases and potentially prolong survival in cancer patients. However, few population-based studies have examined the association between warfarin use and cancer-specific mortality. Methods: Using prescribing, cause of death, and cancer registration data from the UK Clinical Practice Research Datalink, four population-based cohorts were constructed, comprising breast, colorectal, lung, and prostate cancer patients diagnosed between 1 January 1998, and the 31 December 2010. Comparing pre-diagnostic warfarin users to non-users, multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) for cancer-specific mortality. Results: Overall, 16,525 breast, 12,902 colorectal, 12,296 lung, and 12,772 prostate cancers were included. Pre-diagnostic warfarin use ranged from 2.4 to 4.7 %. There was little evidence of any strong association between warfarin use pre-diagnosis and cancer-specific mortality in prostate (adjusted HR 1.03, 95 % CI 0.84–1.26), lung (adjusted HR 1.06, 95 % CI 0.96–1.16), breast (adjusted HR 0.81, 95 % CI 0.62–1.07), or colorectal (adjusted HR 0.88, 95 % CI 0.77–1.01) cancer patients. Dose–response analyses did not reveal consistent evidence of reductions in users of warfarin defined by the number of prescriptions used and daily defined doses. Conclusions: There was little evidence of associations between pre-diagnostic use of warfarin and cancer-specific mortality in lung, prostate, breast, or colorectal cancer patients.