Canadian Cancer Society’s perspective on aspirin and cancer

31 October 2013

Over the past few years, a number of research studies have looked at the potential benefits of aspirin in relation to cancer. These studies have found that a daily aspirin can reduce the risk of certain cancers and cancer death.

Our perspective

While the Canadian Cancer Society finds this research promising, we do not recommend that Canadians take aspirin in order to reduce their risk of cancer or cancer death. There could be possible harmful effects of taking low-dose aspirin for long periods of time, including risk of bleeding and gastrointestinal complications.

More research is needed to better understand the relationship between aspirin and cancer before we can make a recommendation.


The research to date about aspirin and cancer has shown that:

  • Daily aspirin use (minimum 75 mg dose, sometimes called a baby aspirin) over a period of 5 years or longer can reduce the 20-year risk of death from esophageal, colorectal and lung cancer in men. The 75 mg daily dose of aspirin was as effective as higher doses (75-300 mg).
  • For men and women, low-dose daily aspirin use (less than 300 mg) can reduce the risk of getting cancer (about 3 years after starting to take it) and death due to cancer (about 5 years after starting to take it).
  • Daily aspirin use can reduce the risk of cancer spreading to other parts in the body.

The research so far shows trends, but it is not enough to make a recommendation for aspirin and cancer prevention. More research is needed to better understand the relationship between aspirin and cancer, including:

  • more research specifically about aspirin and cancer. The analyses to date are from randomized controlled trials that were designed to study cardiovascular disease, not cancer. The Women’s Health Study and Physicians’ Health Study are 2 large trials in primary prevention with cancer as a pre-identified outcome. The Physicians’ Health Study did not find a preventive effect when participants took aspirin every other day. The Women’s Health Study found that aspirin every other day can reduce the risk of colorectal cancer, but it increases  the risk of gastrointestinal complications.
  • research to better understand the risks of taking aspirin for long periods of time. 
  • research on the specific mechanisms of how aspirin affects cancer.
  • research to understand who is likely to benefit most from using aspirin. Some research has shown that aspirin’s effects on cancer occur regardless of other risk factors such as smoking, sex and body mass index (BMI). However aspirin may be more beneficial for older adults.