Can aspirin help prevent colorectal cancer development and progression?

By Staff 8 Min Read

  • Regular use of low-dose aspirin could potentially stop or slow the progression of colorectal cancer.
  • Researchers report that right-sided colorectal cancers had a more pronounced effect from taking daily aspirin than tumors found on the left side of the colon.
  • Experts caution that daily aspirin use may cause gastrointestinal or brain bleeding. They say the benefits and risks should be carefully considered and discussed with your physician before beginning an aspirin regimen.

Taking low-dose aspirin over a long period of time might slow or even prevent the progression of colorectal cancer, according to a study published by today in CANCER, a peer-reviewed journal of the American Cancer Society.

Researchers conducted a study of tissue samples from people with colorectal cancer who used aspirin and others who didn’t in order to gain insight into how aspirin could slow the progression of the cancer.

Scientists say they are not sure why aspirin provides these benefits, but they speculate it might be because the pain medication boosts certain aspects of the immune response against cancer cells.

The researchers examined tissue samples from 238 people who had had surgery for colorectal cancer. About 12% of the participants were aspirin users.

The researchers compared those who used aspirin to those who did not. They say they discovered that in people who regularly took aspirin, cancer spread to lymph nodes at a lower rate. They added that aspirin users also had a higher infiltration of immune cells into their tumors.

When the scientists exposed cancer cells to aspirin in the lab, they noted an increase in the protein CD80, enhancing cells’ ability to alert other immune cells to tumor-associated proteins. People with colorectal cancer had higher levels of CD80 in their healthy rectal tissue.

The researchers believe these findings indicate a pro-immune surveillance effect of aspirin.

“Our study shows a complementary mechanism of cancer prevention or therapy with aspirin besides its classical drug mechanism involving inhibition of inflammation,” Dr. Marco Scarpa, a surgeon at the University of Padova in Italy and a principal investigator in the study, said in a press release. “Aspirin is absorbed in the colon by passive diffusion to a significant degree. Its absorption is linear and depends on concentration along the bowel, and in the rectum, the concentration of orally administered aspirin can be much lower than in the rest of the colon. Thus, if we want to take advantage of its effects against colorectal cancer, we should think of how to guarantee that aspirin reaches the colorectal tract in adequate doses to be effective.”

There were several limitations of the study:

  • It was a retrospective and observational study, which are typically not as accurate as direct studies.
  • The researchers did not know the dose or duration of preoperative aspirin use.
  • Aspirin use was self-reported.
  • There was a small sample size.

Nonetheless, one expert said the findings are important.

“This is a fascinating and important study,” said Dr. Anton Bilchik, a surgical oncologist, chief of medicine, and director of the Gastrointestinal and Hepatobiliary Program at Providence Saint John’s Cancer Institute in California.

“It provides more information on the benefits of aspirin for colorectal cancer,” Bilchik, who wasn’t involved in the study, told Medical News Today. “Many previous studies have looked at the risk factors for colon cancer. This one looks at progression. The researchers found that low-dose aspirin positively affected the immune system. Although, there was a relatively small sample size.”

The researchers said there was a stronger effect from aspirin on right-sided colon cancer than on left-sided cancers.

Right-sided and left-sided colon cancers are considered distinct cancers. There are differences in epidemiology, pathology, and prognosis. People with right-sided colon cancer are more likely to be older, female, and have more advanced tumors at diagnosis, according to a 2022 report in the journal Nature.

“Right-side cancer is completely different than left-side cancer,” Bilchik said. “The different parts of the colon behave differently, including during the onset and progression of cancer. The scientists found less lymph node involvement in people taking daily aspirin.”

Symptoms can be different based on which side of the colon the cancer is.

Symptoms of right-sided colon cancer include:

  • Blood in the stool
  • Anemia
  • Unexplained weight loss

Symptoms of left-sided colon cancer include:

  • A change in bowel habits
  • Constipation
  • Ribbon-shaped, narrow stools

There is a poorer prognosis for right-sided colon cancer than for cancers on the left, according to a 2023 study published in the journal Cureus.

Medical experts have touted the benefits of low-dose aspirin for heart and stroke prevention. That’s partly because aspirin acts as a blood thinner and therefore can decrease the risk of blood clots.

A study completed in 2023 reported that over-the-counter aspirin provided the same benefits as an injected blood thinner after certain types of surgery.

Recent information has questioned aspirin use based on potential side effects. Some researchers report that daily aspirin use can potentially cause bleeding in the brain or gastrointestinal tract. The risk increases with age.

The United States Preventive Service Task Force (USPSTF) recommends against starting a daily aspirin regimen to help prevent cardiovascular disease for people over 60 years of age.

According to the University of Maryland Medical System, people who should not take daily aspirin include:

  • Those who are 60 or older and not at risk of heart attack or stroke
  • Those at a higher risk of gastrointestinal bleeding or hemorrhagic stroke
  • Those who drink alcohol on a regular basis
  • Those with an allergy to aspirin
  • Those who will have a medical or dental procedures in the near future

However, the recommendations do suggest that low-dose aspirin can help in the secondary prevention of people with atherosclerotic cardiovascular disease or who have existing heart problems, such as a history of heart attack, stroke, angioplasty, or other heart issues.

People who are likely to benefit from daily aspirin, according to the University of Maryland Medical System include people who:

People 40 to 59 years of age who have a 10% or greater 10-year cardiovascular risk may benefit from aspirin use, but the USPSTF suggests the benefit is small. However, those who do not have an increased risk of bleeding may benefit.

“Whether low-dose aspirin should be taken or not is the million dollar question,” Bilchik said. “The benefits and risks should be carefully weighed. The recommendation to take or not to take is a judgment call by a physician who knows your health history.”

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