Should you take aspirin to prevent colorectal cancer?


Excluding skin cancers, colorectal cancer is the third-leading cause of cancer-related deaths in the United States. Regular colorectal cancer screening is the best way to reduce risk. But for certain people, taking a daily low-dose aspirin should also be on your to-do list.

The U.S. Preventive Services Task Force (USPSTF) finds that low-dose aspirin can reduce the risk of colorectal cancer by 40% for people who meet specific criteria.

Still, “as with every medical or surgical therapy, we need to weigh the benefits against the risks,” says UCLA Health gastroenterologist Mona Rezapour, MD, MHS. Not adhering to the USPSTF guidelines could leave you at high risk for gastrointestinal (GI) bleeding, the biggest danger associated with aspirin use.

“We know that aspirin reduces the risk of colorectal cancer, but we don’t recommend it to the general population yet because the benefits don’t outweigh the risks for everyone,” Dr. Rezapour says.

Wondering if you should be taking aspirin to reduce your cancer risk? Dr. Rezapour explains what you need to know.

How aspirin reduces the risk of colorectal cancer

Like many forms of cancer, colorectal cancer can stem from inflammation. Aspirin, a type of nonsteroidal anti-inflammatory drug (NSAID), works to hinder inflammation before it can cause damage.

“Aspirin inhibits several colon cancer-related pathways and inhibits inflammation, which over time leads to cancer,” Dr. Rezapour says. She suggests thinking about cancer as fire spreading quickly through the body. Chronic inflammation is the fuel for that fire. Aspirin is the cooling agent that suppresses the fire and dampens its progression.

Newer research shows aspirin also playing a role in the gut microbiome. “Aspirin promotes the growth of good bacteria in the gut,” Dr. Rezapour says. “Those are the bacteria that help prevent colorectal cancer progression and development.”

Guidelines for low-dose aspirin use

Both the USPSTF and the American College of Gastroenterology (ACG) agree that for a select group of people, the benefits of daily low-dose aspirin use outweigh the risks. Before recommending a low-dose aspirin regimen, your primary care provider will look at all of the following factors:

Your risk of cardiovascular disease

The USPSTF only recommends low-dose aspirin for people who have a 10% or greater 10-year cardiovascular disease (CVD) risk. According to Dr. Rezapour, the reason for this guideline is two-fold. People with that CVD risk are:

  • Likely to already be taking baby aspirin: Aspirin can reduce risk of cardiovascular complications, so many people with an increased risk are already on a low-dose aspirin regimen. Studies show the benefits of aspirin already outweigh the risks for this population.
  • At a higher risk for colon cancer: Patients who have an increased risk of CVD often have other issues associated with increased inflammation, such as diabetes, obesity or hypertension. Those other issues increase the risk for colorectal cancer.

Your age

The majority of colorectal cancers occur in people older than 50. But the USPSTF guidelines recommend the use of aspirin only for adults age 50 to 59.

If you are age 60 to 69, the decision to use low-dose aspirin is an individual one and should be discussed with your physician. For adults under age 50 or age 70 and older, there is currently not enough evidence to support low-dose aspirin use.

“We still don’t fully understand the dose, frequency or effectiveness of aspirin for people who are at average risk for colorectal cancer,” Dr. Rezapour says. “Until we have a better understanding of these factors, we need to restrict the age group in recommending aspirin.”

Your risk of gastrointestinal (GI) bleeding

One of the biggest issues with aspirin is the risk of GI bleeding that comes with it, according to Dr. Rezapour. “The risk of GI bleeding can be really high and includes stroke and massive hemorrhage. We have to think carefully about who should be taking aspirin.”

According to the USPSTF, risk factors for GI bleeding with aspirin use include:

  • Being male
  • Concurrent use of NSAIDs or anticoagulants (medicines to prevent blood clots)
  • GI pain
  • GI ulcers
  • Older age
  • Uncontrolled hypertension (high blood pressure)

Your ability to commit to a 10-year aspirin regimen

Both the USPSTF and the ACG stress that you have to be willing or able to take aspirin for at least a decade. “The reason is that research shows that we see the full effect of aspirin on colorectal cancer prevention after 10 years of use,” Dr. Rezapour says.

When determining whether an aspirin regimen is right for you, your life expectancy will play a role along with your willingness to take low-dose aspirin daily for at least 10 years.

To learn more about colorectal cancer screening and whether you should be taking aspirin to reduce your cancer risk, talk to your primary care provider.