Warfarin may have anti-tumor properties, and warfarin-use was associated with a reduced relative risk of all cancer types, according to a study published in JAMA Internal Medicine.1

There is a growing need to elucidate the impact of warfarin, which inhibits pathways necessary for oncogenesis, on cancer prevention.

For this population-based cohort study, researchers analyzed the health outcomes of 1,256,725 patients and separated them into warfarin- and non-warfarin-using subgroups. Researchers defined warfarin-use as at least 6 months of use as determined by prescription history and at least 2 years of use from the first prescription filled to disease diagnosis.

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Of the enrolled patients, 7.4% were warfarin users and 92.6% were non-users; 10.6% of all patients in the cohort had cancer.

There was a significantly lower incidence rate ratio (IRR) for all cancer sites once adjusted for age and sex among patients using warfarin compared with non-users (IRR, 0.84; 95 %CI, 0.82-0.86), and for 3 of the 4 most prevalent cancer sites: lung (IRR, 0.80; 95% CI, 0.75-0.86), prostate (IRR, 0.69; 95% CI, 0.65-0.72), and breast (IRR, 0.90; 95% CI, 0.82-1.00).

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A subgroup analysis of patients with atrial fibrillation or atrial flutter also revealed a lower IRR in all cancer sites (IRR, 0.62; 95% CI, 0.59-0.65), and for all 4 of the most prevalent cancer sites: lung (IRR, 0.39; 95% CI, 0.33-0.46), prostate (IRR; 0.60; 95% CI, 0.55-0.66), breast (IRR, 0.72; 95% CI, 0.59-0.87), and colon (IRR, 0.71; 95% CI, 0.63-0.81).

The authors concluded that these findings “may have important implications for choosing medications for patient who need anticoagulation. Further studies are warranted to fully elucidate the mechanisms underpinning these observations.”


  1. Haaland GS, Falk RS, Straume O, Lorens JB. Association of warfarin use with lower overall cancer incidence among patients older than 50 years. JAMA Intern Med. 2017 Nov 6. doi: 10.1001/jamainternmed.2017.5512 [Epub ahead of print]