JAMA study says blood-thinner warfarin cuts cancer risk by up to 61%; now they tell us.

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The News:

A medicine widely taken to prevent heart attack and stroke may also guard against cancer, new research suggests.

Warfarin is an inexpensive blood thinner, US News points out. It’s typically prescribed for patients whose leg arteries are prone to clots and for patients with the abnormal heartbeat called atrial fibrillation.

Now, Norwegian investigators say it may also protect against any type of cancer and from prostate, lung and breast cancer, in particular. Lower colon cancer risk was also reported, but only in people taking warfarin for A-fib, according to the study.

“This is an observational study using data on more than 1.25 million people 50 and older from Norwegian national registries, and cannot prove a cause-and-effect relationship,” said lead researcher James Lorens, a professor of biomedicine at the University of Bergen in Norway.

Among adults taking warfarin, however, fewer developed cancer compared with those not taking the drug, Lorens said.

This study suggests there is something about warfarin that might reduce the risk of cancer, said Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society.

However, “the study does not suggest that we should be prescribing warfarin to reduce cancer risk,” he said. “No one should be taking warfarin as a cancer prevention measure.”

Lichtenfeld added that a healthy diet and exercise are better ways to prevent cancer than taking warfarin.

Experimental cancer models have found that warfarin blocks a receptor called AXL on tumor cells, which might explain why it could prevent cancers, Lichtenfeld said.

As many as 10% of adults in Western countries take warfarin, according to background notes with the study. As a blood thinner, warfarin works by blocking vitamin K, which is essential for clotting. But the drug is difficult to regulate, and frequent blood tests are needed to ensure the dose is high enough to prevent clotting, but not so high as to cause major bleeding.

New drugs that don’t need such careful monitoring, such as Xarelto (rivaroxaban) and Eliquis (apixaban), have started to replace warfarin. Because these new drugs have a different mechanism of action, “we do not expect the same cancer protective effect as warfarin,” Lorens noted.

Rolf Brekken is a professor of surgery at the Center for Therapeutic Oncology Research at the University of Texas Southwestern Medical Center in Dallas. He hopes to see a trial testing warfarin in patients who have had cancer.

“The next step is to demonstrate that a low dose of warfarin is safe and effective in preventing a return of cancer,” Brekken said.

Steve’s Take:

I recently wrote a piece describing how researchers have concluded that blood thinners like warfarin may protect against dementia. Now, we’re finding that warfarin–taken to prevent blood clots, strokes and heart attacks–reduced the cancer threat for all patients using it.

Scientists believe warfarin reduces the risk of cancer by boosting the immune system’s ability to kill tumor cells.

Steve's Take: Amazing that #Warfarin, in use for 50+ years, can reduce #Dementia and #Cancer Click To Tweet

But for those with an irregular heartbeat–a common condition known as atrial fibrillation–it was even more effective.

Those people saw their chance of getting any cancer reduced by 38% and of getting lung cancer by an eye-popping 61%.

Lead researcher James Lorens sums up the JAMA study saying: “Our main finding is that a drug that has been in clinical use for more than 50 years and used by millions of adults worldwide, may protect against cancer.”

And this wasn’t a small sample, randomly thrown together. No, warfarin’s potential to protect against cancer emerged from a study of 1.2 million over-50-year-olds.

The researchers say warfarin cuts the risk of getting any cancer by 16%. And they warn switching to newer clot-busting drugs will lead to more cancer cases.

I read the entire JAMA study, and here are some of the verbatim conclusions the researchers articulated that make this finding so stunning.

  • “Our large population-based study with a subgroup analysis of patients with arrhythmia reveals a remarkable association between warfarin use and lower cancer incidence across a broad range of malignant neoplasms. The well-known challenges of warfarin dosing that necessitate regular monitoring have fueled a transition to new oral anticoagulants. 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.”


  • “A large number of patients with AF were identified in the cohort, and the association between warfarin use and lower cancer incidence in this subgroup was stronger compared with that in groups in the main analysis. This finding supports the hypothesis that warfarin may exert considerable cancer protection against major carcinoma types.”


  • “[The] observed association between warfarin use and lower cancer incidence is likely due in part to an enhanced antitumor immune surveillance of early cancer. Congruently, warfarin is associated with immune activation, and autoimmune disorders are reported as an adverse effect.”


  • “Our data indicate that warfarin provides a possible cancer protection, a finding that may have important implications for choosing medications for patients who need anticoagulation.”

Here’s a summary of my earlier piece on warfarin and its connection to dementia, the biggest subcategory of which is Alzheimer’s:

Anticoagulant drugs may protect against dementia as well as stroke in people with an irregular heartbeat, new research suggests.

A Swedish study found that patients being treated for atrial fibrillation were less likely to develop dementia if they were taking anticoagulants.

Their risk was reduced by up to 48% compared with others with the same condition who were not prescribed the drugs. The study, published in the European Heart Journal, found no difference in dementia prevention between the older blood-thinning drug warfarin and newer anticoagulants.

Researchers found that of 444,106 patients in Sweden who had atrial fibrillation, an abnormal heart condition that can provoke strokes, those taking drugs to prevent blood clots had a 29% lower risk of developing dementia. The risk further decreased as patients continued to take the medication. The study is the largest ever on the link between anticoagulants and dementia in atrial fibrillation patients.

Dr. Friberg from the Karolinska Institute, who co-led the above study, said: “As a clinician I know there are AF patients who have a fatalistic view on stroke. Either it happens, or it does not. [But] few patients are fatalistic about dementia, which gradually makes you lose your mind.”

Not exactly subtle, but I the good doctor’s matter-of-fact choice of words.

Bottom Line:

It’s important to understand that these jaw-dropping studies don’t recommend that everyone rush to their doctor to get on warfarin. Such medicines are primarily indicated where there is an increased risk of stroke due to blood clot. And they do have the increased bleeding risk. Just happens that they also cut a user’s risk of dementia by half and cancer by up to 60%.

After all the time, effort, science and funding, warfarin, which has been in use for over fifty years, has been systematically ushered out of pharmacies with the advent of newer, pricier types of anticoagulants–like Xarelto and Eliquis. Now, researchers are saying: Not so fast. I say, better late than never.

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