Can an Aspirin a Day Keep Cancer Away?

Aspirin has been called the one-cent miracle drug, and it remains the most famous and most widely used drug in the world. Still, it is easy to take aspirin for granted. It's what our grandparents took when they had a headache or fever, but most of us have moved on to other pain relievers.

Millions of healthy people take low-dose aspirin to help prevent heart attacks but this benefit appears to be smaller than once thought—especially when compared to the effect of statin drugs, or statins. We haven't figured out all the complex effects that aspirin has on body chemistry, however, and it continues to make headlines. Recently the news was about aspirin's potential as an anti-cancer drug.

Actually, it's not a surprise that aspirin may reduce the risk of cancer. Lab and animal studies have found that it can slow or prevent the growth of tumor cells. And in many observational studies, people taking aspirin have had lower rates of precancerous colorectal polyps (adenomas), colorectal cancer, and some other cancers. Some of the evidence suggests that other nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may also reduce the risk.

In January 2011, the strongest case yet for aspirin's anti-cancer potential was made by an analysis in The Lancet. It combined data from eight randomized clinical trials on aspirin therapy for cardiovascular disease, which involved 25,570 people and lasted four to eight years. The conclusion: Daily aspirin reduced total cancer deaths by 34 percent after five years. And 15 years later, long after the trials had ended, death rates among aspirin groups were still 20 percent lower, with the biggest drops in esophageal, colorectal, lung, and prostate cancer, in that order. The longest studies found the greatest reductions in cancer deaths. The studies included mostly men, so breast cancer risk could not be evaluated.

Low Dose Aspirin, Big Anti-Cancer Benefit

One promising finding was that the anti-cancer benefit was not related to the dose of aspirin. In fact, the low doses used for heart health (75 to 81 milligrams, the amount in a "baby" aspirin or one quarter of a standard tablet) were just as effective as larger amounts. Some earlier studies that suggested anti-cancer effects had focused on heavy aspirin use, which was a concern because the higher the dose, the greater the risk of adverse effects. However, several recent studies looking at aspirin and colorectal cancer have concluded that low daily doses are also protective. And the new analysis found that this may be true of some other cancers as well.

Aspirin reduces inflammation, which plays a role in cancer development and/or growth. It's also theorized that aspirin may be involved in the death of early cancer cells and have other anti-cancer effects.

A Balancing Act between Aspirin Risk and Benefits

Many doctors have rightly hesitated to recommend low-dose aspirin for healthy people because the small risk of stomach or intestinal bleeding, ulcers and hemorrhagic ("bleeding") strokes at least partly offsets the heart benefits. But adding in aspirin's anti-cancer potential may well tip the balance in favor of benefits for many people, especially if aspirin is started in middle age.

"Potential" is a key word here. As strong as the new analysis is, the studies it included were not designed to look at cancer, and that can complicate the interpretation of the results. So it's still too soon to recommend aspirin therapy for everyone. Of course, most people who have cardiovascular disease or who are at high risk for it should take low-dose aspirin.

Based on this and previous research, others should consider it, too, especially those at high risk for colon cancer because they've had polyps or have a family history, or those who already have the disease.

"The new study suggests that the risk of bleeding from low-dose aspirin is offset by the reduction in deaths from colorectal cancer and perhaps other types of cancers as well," according to Dr. Steven Jacobsohn, a gastroenterologist and Clinical Professor of Medicine at the University of California, San Francisco. "It’s not clear at what age people should start. The benefit isn't immediate, so starting at age 45 for patients with average risk factors for colorectal cancer seems reasonable. Someone with a family history of colorectal cancer might start at age 40. These findings do not alter the need to continue colorectal cancer screening."

Bottom line: The best evidence for aspirin's anti-cancer effect concerns colorectal cancer. But if you're at high risk for some other cancers, you may also want to consider daily low-dose aspirin. Some people, including those who have had ulcers or are taking certain drugs, are at elevated risk for adverse effects from aspirin. So, if you're considering aspirin therapy, it's important to talk to your doctor first.

Source: Originally published in The University of California, Berkeley Wellness Letter (April 2011)

Publication Review By: the Editorial Staff at

Published: 31 Mar 2011

Last Modified: 03 Sep 2015