Low-dose ASA is already known to prevent heart attacks and strokes in certain patients. Now, new research suggests the little white pill might be able to reduce deaths from several common cancers.

The research, published in The Lancet medical journal, was pulled from eight large studies that were designed to compare heart and stroke events among those taking ASA and those who didn't (ASA stands for acetylsalicylic acid, and is commonly sold as aspirin).

The research team, led by Dr. Peter Rothwell, a neurologist at Oxford University, reviewed the data involving more than 25,000 patients and found that not only did low dose ASA reduce bowel cancer cases – as previous research has found – it also appeared to affect the death rates of several other common cancers, including esophageal, prostates and lung cancer.

The team found there were at least 20 per cent fewer deaths from cancer among patients who took between 75 mg and 300 mg of ASA each day, compared to those who didn't take ASA. The 20-year risk of death was reduced by about:

  • 10 per cent for prostate cancer
  • 30 per cent for lung cancer
  • 40 per cent for colorectal or bowel cancer
  • 60 per cent for esophageal cancer in those taking aspirin.

The benefits were found in both genders and seemed to increase with age.

It's not clear why ASA might be linked to lower cancer death rates. But previous research has found the drug blocks the enzyme cyclooxygenase2, which promotes inflammation and cell division and is found in high levels in cancer tumours.

The researchers say that ASA may need to be taken for at least five years before it offers any cancer-prevention benefit – and maybe even longer for some cancers. But they say the benefit generally appears greater the longer ASA has been taken.

The researchers note that ASA can increase the risk of bleeding. In fact, for patients who aren't at risk of a heart attack or stroke, the benefit of ASA may be outweighed by the risk of bleeding.

But the authors say their findings could alter clinical advice about low dose ASA, "because the balance between benefit and bleeding has probably been altered towards using it."

The authors stress that their results don't mean every adult should start taking ASA. But they do suggest additional benefits of the drug are not currently factored into guidelines for preventing cardiovascular events.

The Canadian Cancer Society responded to the study with caution, saying that while it welcomes the study, "it's certainly not anything that would be enough to start making recommendations to the public."

"One of the limitations is that because the study was looking at cardiovascular events, it wasn't designed in such a way to take into account the other factors that impact cancer deaths," CCS's Heather Chappell, director of cancer control policy, told The Canadian Press.

Furthermore, she noted, the researchers looked only at cancer deaths -- not the risk of developing the disease.