Long-term daily use of aspirin could help prevent the development and progression of colorectal cancer, a recent study has revealed.

According to the study published in Cancer, a peer-reviewed journal of the American Cancer Society, regular aspirin use may have an active role in enhancing immunosurveillance against colorectal cancer.

"Our study shows a complementary mechanism of cancer prevention or therapy with aspirin besides its classical drug mechanism involving inhibition of inflammation," said principal investigator, Dr. Marco Scarpa from the University of Padova, Italy.

Colorectal cancer ranks as the third most prevalent cancer globally and the fourth leading cause of cancer-related deaths. Numerous studies have shown the potential of aspirin, a nonsteroidal anti-inflammatory drug in boosting certain aspects of the body's immune response against cancer cells.

In the latest study, investigators obtained tissue samples from 238 patients enrolled in the IMMUNOlogical microenvironment in the REctal Adenocarcinoma Treatment (IMMUNOREACT 8), a multicenter observational study. The participants were those who underwent surgery for colorectal cancer in 2015–2019. Of the total participants, 12% were aspirin users.

While conducting a comparison between aspirin users and non-users, they found that among individuals who regularly took aspirin, the rate of cancer spreading to lymph nodes was lower. Additionally, they also observed a higher presence of immune cells infiltrating the tumors of aspirin users.

When the colorectal cancer cells were exposed to aspirin in their lab, researchers noticed an increase in the expression of a protein called CD80 on specific immune cells. As per the study authors, this allowed immune cells to communicate more effectively with other immune cells about the presence of proteins linked to cancer cells.

Furthermore, higher CD80 expression was seen in the healthy rectal tissue of patients with rectal cancer. This discovery suggests that aspirin may create an environment where the immune system is more vigilant in detecting cancer cells.

However, the study has not examined the underlying mechanisms by which aspirin prevents colorectal cancer.

"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," Dr. Scarpa explained.

The study has certain limitations. The retrospective and observational nature of the study and small sample size are a few of those. The exact dose or duration of aspirin use is also not known and the researchers relied on self-reported data.