Aspirin: Could It Reduce Your Risk for Cancer?

Nyedra W. Booker, PharmD, MPH


Often called a “wonder drug,” aspirin reduces aches and pains, fever, and swelling, and lowers the risk of heart attack and stroke.  But few of us ever imagined that it might also lower our chances of developing several types of cancer, and help keep cancer from spreading.

How does aspirin prevent and fight cancer? Aspirin and many other pain killers reduce inflammation, and inflammation can contribute to the development of certain cancers.1 Besides its anti-inflammatory properties, aspirin also activates a protein (adenosine monophosphate-activated protein kinase or AMPK) that helps control how fast cells grow and change in the body. 2

The earliest and strongest evidence that aspirin can prevent cancer emerged from studies showing that a daily dose of aspirin reduced the risk of colorectal cancer by 20%.3 Early on, it appeared that people had to take aspirin for at least five years to reduce their risk of developing cancer, but some of the newer studies suggest that 2 years may also help prevent cancer. 4, 5

Analysis of five large studies of daily aspirin use (baby aspirin size or higher dose) in more than 17,000 patients, for the prevention of heart attacks, strokes, and other vascular events, found that people taking aspirin every day were less likely to develop cancer or die from cancer.6 Compared to those who did not take aspirin, the almost 10,000 people who took a daily dose of aspirin reduced their risk of dying from colorectal and prostate cancers. The people taking aspirin who were diagnosed with colorectal, lung or brain cancer during the studies were also less likely to have their cancer spread (metastasize) to other parts of the body or organs. Daily aspirin use for about two years reduced the risk of cancer spreading to other organs, sometimes by as much as 40%. Most important, there were fewer total cancer-related deaths among the people taking aspirin every day.

In another analysis of more than 50 studies of daily aspirin use for the prevention of vascular events such as stroke, aspirin reduced the risk of both cancer and non-cancer related deaths. 7 In the 34 studies (more than 69,000 participants) that included information about participants developing and dying from cancer, the people who took aspirin were less likely to develop colorectal cancer, uterine cancer, lymphoma and other types of cancer. Fewer deaths from cancer also occurred among the people taking a daily dose of aspirin than among those who took no aspirin.  There were 562 deaths reported in the group taking aspirin, compared to 664 deaths in the group that didn’t take aspirin. The aspirin-takers were almost 40% less likely to die from cancer if they took aspirin for 5 years.

Does the Dose Matter?

A standard dose of aspirin (one pill) is typically 325 mgs, and a low-dose or “baby” aspirin is 81mg. Although called baby aspirin, children under 12 should not take aspirin due to the risk of Reye’s Syndrome. In a study that compared daily use of very low dose aspirin (30mg) to a daily dose of 283mg for preventing vascular events, researchers found no significant difference in cancer deaths between the two groups. In six studies of daily low-dose aspirin use (75 to 100 mg) for preventing vascular events, aspirin reduced the risk for cancer by almost 25% after at least 3 years of aspirin therapy. Daily aspirin use appeared to be particularly beneficial in reducing the risk for certain cancers of the female reproductive organs.7 For instance, there were significantly fewer cases of uterine cancer among the women taking aspirin every day than among the women who didn’t take aspirin (zero cases among women taking aspirin as compared to 9 cases in the non-aspirin group).

At doses as low as 75mg, daily aspirin not only lowered the risk of heart attack and stroke, but it appears to have prevented many types of cancer, including colon cancer and uterine cancer, as well as slowed the spread of cancer to distant organs. Higher aspirin doses, which increase the risk of ulcer and internal bleeding, did not appear to work any better.

While these studies are exciting and reveal aspirin to be more of a wonder drug than we ever imagined, it’s important to remember that aspirin therapy is NOT for everyone. Aspirin belongs to a group of medications known as “blood thinners.” These drugs prevent the body from making potentially harmful clots that can block blood vessels and cause heart attacks and strokes. Patients already taking blood thinners who take aspirin may be at an increased risk for internal bleeding, ranging from mild to life-threatening. Those with severe liver and kidney disease are warned against using aspirin given the potentially toxic effects on these organs. In addition, asthma patients may be particularly sensitive to aspirin and can, as a result, experience asthma-related complications.8

How Often and For How long?

What about taking aspirin every other day? Two of the largest studies of aspirin use for the prevention of cardiovascular disease, the Women’s Health Study (WHS) involving more than 39,000 women, and the Physician’s Health Study (PHS) of more than 22,000 men, had patients take aspirin every other day. The women took 100 mg every other day and the men took 325 mg every other day. Surprisingly, neither study showed a reduction in cancer risk or cancer-related deaths, even after more than 10 years of aspirin therapy. 9,10

For years, people at high risk for heart attack or stroke have been advised to take a low-dose (81 mg) of aspirin every day. Will this recommendation be extended now to people at high risk for certain cancers-either because cancer runs in their family or because they themselves are cancer survivors and want to prevent a recurrence? And what about people newly diagnosed with cancer who want to make sure the cancer stays in as small an area as possible and is, therefore, easier to treat? These are still unanswered questions, as is the question of how many years a person needs to take aspirin every day to get the maximum benefit.

What You Need to Do Before Starting Aspirin Therapy

Remember that aspirin is a drug, and it has risks even at low doses. You should discuss aspirin therapy first with your doctor and let him or her know:

  • Your medical history and the medicines you are currently using, whether they are prescription or over-the-counter
  • Any allergies or sensitivities you may have to aspirin
  • Any vitamins or dietary supplements you are currently taking

Some of us know that aspirin should not be taken with certain other over-the-counter pain medications (NSAIDS), such as ibuprofen (Motrin and Advil) and naproxen (Aleve) because they can increase the risk of internal bleeding. But did you know that is also true for several herbs and nutritional supplements?  Vitamin E, fish oil (omega-3 fatty acids) and what’s known as the “four Gs”-garlic, ginger, gingko, and ginseng-can all increase your risk for bleeding when taken with aspirin and other blood thinners.11

Quitting smoking, eating a diet rich in fruits and vegetables, and avoiding long bouts of sitting (some people make 10,000 paces a day their goal), are great ways to reduce your chance of developing heart disease and cancer-without  any side effects!   For people at highest risk who can’t make these behavior changes, aspirin could truly be a lifesaver.

1 National Cancer Institute. “NCI-Sponsored Trials of Cyclooxygenase (COX) Inhibitors for Cancer Prevention and Treatment. ” Accessed March 21, 2012.

2 Hawley SA, Fullerton MD, Ross FA, et al. The Ancient Drug Salicylate Directly Activates AMP-Activated Protein Kinase. Science. 2012; DOI:10.1126/science.1215327.

3 Rothwell PM, Wilson M, Elwin CE, et al. Long-term effect of aspirin on colorectal cancer incidence and mortality: 20-year follow-up of five randomised trials. Lancet. 2010;376:1741-50.

4  Flossmann E, Rothwell PM. Effect of aspirin on long-term risk of colorectal cancer: consistent evidence from randomized and observational studies. Lancet. 2007;369:1603-13.

5  Rothwell PM, Folkes FG, Belch JF, et al. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Lancet. 2011;377:31-41.

6  Rothwell PM, Wilson M, Price JF, et al. Effect of daily aspirin on risk of cancer metastasis: a study of incident cancers during randomised controlled trials. Lancet. 2012;DOI:10.1016/S0140-6736(12)60209-8.

7 Rothwell PM, Price JF, Fowkes FG, et al. Short-term effects of daily aspirin on cancer incidence, mortality, and non-vascular death: analysis of the time course of risks and benefits in 51 randomised controlled trials. Lancet. 2012;DOI:10.1016/S0140-6736(11)61720-0.

8 FDA. “Aspirin: Questions and Answers.” Accessed March 27, 2012.

9 Cook NR, Lee IM, Gaziano JM, et al. Low-dose aspirin in the primary prevention of cancer: the Women’s Health Study: a randomized controlled trial. JAMA. 2005;294:47-55.

10 Sturmer T, Glynn RJ, Lee IM, et al. Aspirin use and colorectal cancer: post-trial follow-up data from the Physician’s Health Study. Ann Intern Med. 1998;128:713-20.

11 MedlinePlus: Drugs, Supplements, and Herbal Information. Accessed March 30, 2012.