Is Warfarin a Protective Factor for Cancer Among A-Fib Patients? Research Finds a Possible Link

A 7-year retrospective study of patients older than 50 years drawn from the Norwegian National Registry and other databases (1,256,725 persons), found a possible link between warfarin use and cancer prevention. Particularly for A-Fib patients.

Study Participants and Design

Warfarin (brand: Coumadin) tablets

Of the over one million patients in the combined databases, 48.3% were male, 51.7% were female, 7.4% were classified as warfarin users, and 92.6% were classified as nonusers. The participants were divided into 2 groups—warfarin users and nonusers.

Warfarin users had to be taking warfarin for at least 6 months and at least 2 years from first prescription to any cancer diagnosis.

A subgroup were persons taking warfarin for atrial fibrillation or atrial flutter.

Study Findings: Warfarin Users vs. Nonusers

During the 7-year follow-up period, 10.6% (132,687) individuals developed cancer. There were 9.4% cancer diagnoses among the warfarin users and 10.6% among the nonusers.

Warfarin Users vs. Nonusers: Among warfarin users as compared with nonusers, there was a significantly lower incidence of cancer in all organ-specific sites (lung, prostate, and breast, except colon cancer).

A-Fib/A-Flutter group: The effect of warfarin use was more pronounced in the subgroup of patients with atrial fibrillation or atrial flutter for all cancers (lung, prostate, and breast). These patients also had a significant reduction in colon cancer associated with warfarin use.

Interpreting the Study Results

Warfarin use may have broad anti-cancer potential (in patients older than 50).

The study authors believe that warfarin’s vitamin K antagonism is the property that may prevent or hinder the progression of cancer.

They noted 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 cautioned.

James Lorens (University of Bergen) and co-investigators say their findings “could have important implications for the selection of medications for patients needing anticoagulation.”

What This Means to Patients

This begs the question, on the basis of this Norwegian study, “Should A-Fib patients stop taking the new anticoagulants (NOACs) and switch back to warfarin?”  Probably not.

Warfarin blocks vitamin K and has bad side effects: The bad side effects of warfarin use include increased bleeding, hemorrhagic stroke, and microbleeds in the brain.

In addition, warfarin blocks vitamin K absorption, thereby depositing calcium in our arteries and progressively turns them into stone (hardening of the arteries). Vitamin K is essential for heart and bone health. For more, see my article, Stop Taking Warfarin―Produces Arterial Calcification.

Some comfort: If warfarin is your anticoagulant of choice, it’s good to know that it may have anti-cancer properties.