Does regular use of low-dose aspirin improve colorectal cancer survival?
Taking a low-dose daily aspirin long term may reduce the risk of developing or dying from colorectal cancer by revving the body’s immune response to cancer cells, according to a new study published online in CANCER, the peer-reviewed journal of the American Cancer Society.
The new study from Italy reflects other research that suggests low-dose aspirin taken over a period of time could have a real impact in preventing or slowing colorectal cancer by raising the body’s immune response to cancer cells.
In a news release, the researchers say they took tissue samples from 238 patients who underwent surgery for colorectal cancer between 2015 and 2019, 12% of whom regularly used low-dose aspirin, which is a nonsteroidal anti-inflammatory drug. The multicenter study was funded by the Associatzione Italiana per la Ricera sul Cancro and took place primarily at the University Hospital of Padova.
The tissue samples of those who had used low-dose aspirin over time showed less cancer spread to the lymph nodes and that the immune cells were active deeper in the tumors, compared to those who didn’t use aspirin. In the lab, when the aspirin was introduced to the cancer cells, the immune cells expressed more of a protein called CD80, “which enhanced the capacity of the cells to alert other immune cells of the presence of tumor-associated proteins,” the release reported. Related, the researchers said that among patients who had rectal cancer, those who used aspirin had higher levels of the protein in healthy rectal tissue, “suggesting 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,” said Dr. Marco Scarpa, principal investigator, from the university. “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.”
The study did have limitations, as Medical News Today noted. For one thing, it was not a direct study, but was retrospective and based on observation. Plus researchers didn’t know how long or what dose of preoperative aspirin was used.
Right vs. left
But the study “provides more information on the benefits of aspirin for colorectal cancer,” 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, told Medical News Today. He was not involved in the research. “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.”
In colorectal cancer, there’s a difference between right-sided colon cancer and left-sided colon cancer in terms of epidemiology, pathology and prognosis. A 2022 study in Nature said that patients with right-sided colon cancer are more likely to be older, female and have more advanced-stage cancer. It’s also less easy to treat.
The researchers said the low-dose aspirin had a stronger effect on right-sided cancer. Medical News Today noted different symptoms, as well. Right-sided cancer can be marked by bloody stool, anemia and unexplained weight loss, while left-sided cancer features a change in bowel habits, constipation and narrow stool.
Aspirin pros and cons
Like a lot of research, there’s a bit of back and forth here, so it’s worth a conversation with your doctor. At least one other study found aspirin increases risk of bad outcomes in older adults. And some people can’t take aspirin because of increased risk of bleeding, among other contraindications.
Aspirin has been touted for its blood-thinning qualities, so it’s often suggested as a way to prevent stroke or heart attack. But there are people who should not take aspirin for that very quality. According to a post from the University of Maryland Medical System, people should not take aspirin daily if they:
Are at higher risk for gastrointestinal bleeding or brain hemorrhage stroke.
Drink alcohol regularly.
Are allergic to aspirin.
Plan to have a dental or medical procedure soon.
The article also notes possible side effects including diarrhea, itchiness, nausea, skin rashes and stomach pain.
