Warfarin Use and Cancer Risk

Study Questions:

What is the association between warfarin use and cancer incidence?

Methods:

Using a population-based cohort study, all Norwegian people born between 1924 and 1954, who resided in Norway between 2006 and 2012, were included. Participants were divided into warfarin users (≥6 months) and nonusers. Cancer occurring >2 years after initiating warfarin was analyzed.

Results:

Of the 1,256,725 persons, 92,942 (7.4%) were included in the warfarin user group. Warfarin users had a lower age- and sex-adjusted incidence rate ratio (IRR) for all identified cancer sites (IRR, 0.84; 95% confidence interval [CI], 0.82-0.86), along with lung (IRR, 0.80; 95% CI, 0.75-0.86), prostate (IRR, 0.69; 95% CI, 0.65-00.72), and breast (IRR, 0.90; 95% CI, 0.82-1.00) cancer. There was no significant difference for colon cancer (IRR, 0.99; 95% CI, 0.92-1.06). IRRs were lower for warfarin users versus nonusers in the subgroup of atrial fibrillation patients.

Conclusions:

The authors concluded that warfarin use may have broad anticancer potential at a large population level.

Perspective:

Prior studies have been conflicted as to the association between warfarin use and a reduction in cancer risk. This large, nationwide study lends data to support a reduction in cancer risk among warfarin users. Although observational studies are not conclusive, it remains to be seen if there is an association between incident cancer and any chronic anticoagulant use (including the direct oral anticoagulants) or just warfarin. Preliminary work suggests that warfarin may have unique tumorigenesis blocking properties. Similar work should be done with the direct oral anticoagulants.

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Prevention, Anticoagulation Management and Atrial Fibrillation, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Breast Neoplasms, Carcinogenesis, Cell Transformation, Neoplastic, Colonic Neoplasms, Lung Neoplasms, Neoplasms, Prostatic Neoplasms, Secondary Prevention, Risk Reduction Behavior, Warfarin


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