medwireNews: Warfarin use is associated with reduced cancer incidence across a wide range of malignant neoplasms, Norwegian population-based data show.
James Lorens (University of Bergen) and co-investigators say their findings “could have important implications for the selection of medications for patients needing anticoagulation.”
The researchers explain that “[i]n cancer models, warfarin inhibits AXL receptor tyrosine kinase–dependent tumorigenesis and enhances antitumor immune responses at doses not reaching anticoagulation levels.” However, data from epidemiologic studies give conflicting results.
To address this, Lorens and team analyzed nationwide registry data for all individuals born in Norway between 1924 and 1954 who were still living there from 2006 to 2012 (n=1,256,725, 48.3% men).
Of these, 92,942 (7.4%) were warfarin users, receiving the anticoagulant for 4.8 years, on average.
During the 7-year follow-up period, 132,687 (10.6%) individuals developed cancer. There were 8754 (9.4%) cancer diagnoses among the warfarin users and 123,933 (10.6%) among the nonusers.
After adjustment for age and sex, because warfarin users were older (70.2 vs 63.9 years) and more likely to be men (61.7%), warfarin users had a significantly lower rate for cancer overall than nonusers, at an incidence rate ratio (IRR) of 0.84.
The incidence of three of the four most prevalent organ-specific cancers – lung, prostate, and breast – was also lower among warfarin users versus nonusers, at IRRs of 0.80, 0.69, and 0.90, respectively. But there was no significant reduction in colon cancer associated with warfarin use.
The effect of warfarin use was more pronounced in a subgroup of patients with atrial fibrillation or atrial flutter (n=33,313): the respective IRRs for all cancers, and lung, prostate, and breast cancers were 0.62, 0.39, 0.60, and 0.72. These patients also had a significant reduction in colon cancer (IRR=0.71) associated with warfarin use.
Discussing their findings, Lorens et al point out that new oral anticoagulants that require less monitoring are being used more often.
“An unintended consequence of this switch to new oral anticoagulants may be an increased incidence of cancer, which is an important consideration for public health,” they caution in JAMA Internal Medicine.
By Laura Cowen
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