A new study published in JAMA Intern Medicine has reported that Warfarin, used by millions of adults worldwide, might be associated with lower cancer incidence across a broad range of malignant neoplasms.

In cancer models, warfarin inhibits AXL receptor tyrosine kinase–dependent tumorigenesis and enhances antitumor immune responses at doses not reaching anticoagulation levels. In the present, researchers investigate the association between warfarin use and cancer incidence in a large, unselected population-based cohort. In this population-based cohort study of 1?256?725 persons, there was a significantly lower age- and sex-adjusted incidence rate ratio of cancer among warfarin users vs nonusers.

The population-based cohort study with subgroup analysis used the Norwegian National Registry coupled with the Norwegian Prescription Database and the Cancer Registry of Norway. The cohort comprised all persons born between January 1, 1924, and December 31, 1954, who were residing in Norway from January 1, 2006, through December 31, 2012. The cohort was divided into 2 groups—warfarin users and nonusers; persons taking warfarin for atrial fibrillation or atrial flutter were the subgroup.

Warfarin use was defined as taking at least 6 months of a prescription and at least 2 years from first prescription to any cancer diagnosis. If warfarin treatment started after January 1, 2006, each person contributed person-time in the nonuser group until the warfarin user criteria were fulfilled. Of the 1?256?725 persons in the cohort, 607?350 (48.3%) were male, 649?375 (51.7%) were female, 132?687 (10.6%) had cancer, 92?942 (7.4%) were classified as warfarin users, and 1?163?783 (92.6%) were classified as nonusers.

Warfarin users were older, with a mean (SD) age of 70.2 (8.2) years, and were predominantly men (57 370 [61.7%]) as compared with nonusers, who had a mean (SD) age of 63.9 (8.6) years and were mostly women (613 803 [52.7%]). Among warfarin users and compared with nonusers, there was a significantly lower age- and sex-adjusted incidence rate ratio (IRR) in all cancer sites (IRR, 0.84; 95% CI, 0.82-0.86) and in prevalent organ-specific sites (lung, 0.80 [95% CI, 0.75-0.86]; prostate, 0.69 [95% CI, 0.65-0.72]; and breast, 0.90 [95% CI, 0.82-1.00]).

There was no observed significant effect in colon cancer (IRR, 0.99; 95% CI, 0.93-1.06). In a subgroup analysis of patients with atrial fibrillation or atrial flutter, the IRR was lower in all cancer sites (IRR, 0.62; 95% CI, 0.59-0.65) and in prevalent sites (lung, 0.39 [95% CI, 0.33-0.46]; prostate, 0.60 [95% CI, 0.55-0.66]; breast, 0.72 [95% CI, 0.59-0.87]; and colon, 0.71 [95% CI, 0.63-0.81]).

In conclusion, the research team showed that Warfarin use might have broad anticancer potential in a large, population-based cohort of persons older than 50 years. This finding could have important implications for the selection of medications for patients needing anticoagulation.