Could a common drug in your medicine cabinet help prevent colorectal cancer? Possibly, although nothing in cancer prevention is quite that simple, of course. Studies have shown, however, that aspirin may be beneficial for some people.

[See: 10 Health Pros and Cons of Aspirin.]

What’s the Relationship Between Aspirin and CRC Risk?

Aspirin (acetylsalicylic acid) is a chemical derived from the bark of the willow tree that helps relieve pain and fever. It’s been studied widely for its role in preventing cardiovascular disease, and research indicates there’s a link between aspirin and lowered risk for colorectal cancer, too.

In cohort studies, which follow people for a long time, researchers have observed that individuals taking aspirin for 10 or more years (often for heart disease prevention) have lower rates of colorectal cancer. In fact, in one study, they had a 20 to 30 percent reduced risk of developing CRC, says Dr. Ezra Burstein, chief of the division of digestive and liver diseases at UT Southwestern Medical Center. “We understand that cancers of the colon develop in an environment where there is a lot of inflammation,” Burstein says. “The colon is not a sterile environment, like the brain [for example].” According to the National Cancer Institute, prolonged inflammation can promote changes in cells that line the gastrointestinal tract and lead to the formation of polyps (precancerous growths that can develop into tumors). Aspirin reduces inflammation.

Furthermore, Burstein says, early in the development of a tumor, we see an increase in an enzyme called COX-2, which makes prostaglandins, substances that contribute to characteristics of inflammation, such as swelling and pain. If you block COX-2, as aspirin does, it helps avert the growth of tumors and stop new, abnormal growths from developing into tumors.

Data from clinical trials demonstrate that regular aspirin use significantly decreases the risk of colorectal cancer, says Dr. Dale Shepard, a medical oncologist at the Cleveland Clinic. People who take aspirin have fewer polyps and, after removing existing polyps, they are less likely to develop new ones.

Individuals who have a genetic condition called Lynch syndrome, which significantly increases your risk for CRC, may benefit the most from the protective effects of aspirin. In the CAPP2 clinical trial, high doses of daily aspirin in people with Lynch syndrome were associated with a 63 percent reduction in the relative risk of developing colorectal cancer. Relative risk is the risk of a certain event happening in one group compared to the risk of the same event happening in another group.

Aspirin may also help lower your risk of dying from CRC after diagnosis. “Even people who already have cancer and are undergoing treatment, if they are on aspirin after treatment, they do better than those not taking aspirin,” Burstein says.

This benefit is not for every colorectal cancer patient, however. A study published in June 2017 found that among long-term cancer survivors, regular use of non-steroidal anti-inflammatory drugs (such as aspirin) after diagnosis was associated with a 40 percent improved overall survival only in patients whose tumors had the normal version of a specific gene, KRAS wild-type. This applies to about 70 percent of CRC patients. The other 30 percent of patients who have the mutated version of the KRAS wild-type gene didn’t benefit from regular aspirin use.

[See: 8 Questions to Ask Your Doctor About Colon Cancer.]

Risks of Long-Term Aspirin Use

The U.S. Food and Drug Administration has not approved aspirin for CRC prevention, and adopting the regimen isn’t a good idea for everyone, Shepard says, particularly the elderly, those at risk for strokes and individuals with a history of gastrointestinal bleeding.

The U.S. Preventive Services Task Force recommends low-dose aspirin use for the primary prevention of cardiovascular disease and CRC in adults 50 to 59 who have a 10 percent or greater 10-year risk for cardiovascular disease, are not at increased risk for bleeding, have a life expectancy of at least 10 years and are willing to take low-dose aspirin daily for at least 10 years. Adults in their 60s who have the same life expectancy and risks should talk to their doctor about whether taking aspirin makes sense. There is not enough data to recommend for or against preventive aspirin in adults younger than 50 years or older than 70.

[See: 6 Options for People Who Don’t Want a Colonoscopy.]

Screening Far More Beneficial

Both Shepard and Burstein are quick to point out that for people at average risk, the most important way to prevent CRC is to undergo screening. “Screening is so important in this disease,” Shepard says. “So few cancers have screening for them, but we have it for CRC. Find it early, and it makes a difference.”

The NCI says that among people who are screened for colorectal cancer, regular aspirin use provides added risk reduction and may reduce the risk of interval cancers — those that develop in between regular screenings.

More from U.S. News

8 Questions to Ask Your Doctor About Colon Cancer

6 Options for People Who Don’t Want a Colonoscopy

10 Health Pros and Cons of Aspirin

What’s the Link Between Aspirin and Colorectal Cancer Risk? originally appeared on usnews.com