Aspirin Use Helps Immune System Fight Colorectal Cancer: Study

A new study links daily aspirin use to reduced cancer risk, but other research suggests the opposite effect in older people.

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A study published in April in the Journal of the American Cancer Society (ACS) found that taking daily low-dose aspirin may reduce the incidence and death rates of colorectal cancer. In contrast, a large 2020 clinical trial called ASPREE, published in the Journal of the Natural Cancer Institute, suggested that aspirin increases the cancer incidence and death rate in older adults.

Does this mean that aspirin helps some age groups with cancer but not others? The short answer: possibly.

The fact remains that the ACS study’s conclusion aligned with an array of studies that suggest aspirin helps fight colorectal cancer. Yet the large size of the ASPREE trial and the compelling results make it too significant to discount. A research commentary on the ASPREE trial concluded that daily aspirin use may be appropriate only for people at a higher risk of cancer.

Aspirin May Boost Immunity in Cancer

The ACS study from the University of Padoa (UP) in Italy looked at 238 individuals who received a colorectal cancer diagnosis and subsequent surgery from 2015 to 2019. Of these, 12 percent took aspirin regularly. The aspirin users showed:

• Less cancer spread to lymph nodes
• Higher tumor-infiltrating lymphocytes (cells that help fight cancer)
• Increased CD80 protein in colorectal cells
• Increased CD80 protein in healthy tissue surrounding the cancer

In a UP press release, the authors explained the significance of the increased CD80 protein. In cancer cells, it appears to boost the ability to send messages to other defense cells that tumor-associated proteins are present. In healthy cells, it indicates that aspirin may promote an immune surveillance effect.

The ACS study is merely the latest evidence that aspirin is a valuable aid in colorectal cancer prevention. A 2020 review stated that “meta-analyses and other systematic reviews of large observational cohort studies have estimated that aspirin reduces risk for colorectal neoplasia by approximately 20–30%.”

Because of what the review characterizes as “high-quality” findings, health oversight agencies have recommended the use of aspirin for the prevention of colorectal cancer in specific populations. In contrast to colorectal cancer, scientific support for the use of aspirin for the prevention of other cancers is not as strong.

Aspirin May Hasten Cancer Progression

Clinical trials on aspirin as a cancer preventative mainly involve younger people, the ASPREE trial noted. To explore the effect of aspirin use in older adults, it followed 19,114 healthy people aged 70 and older for a median of 4.7 years. The daily dose of aspirin was 100 milligrams. Despite the apparent definitive nature of the ACS study and similar findings from earlier research, the results of the ASPREE trial merit a close look.

The results showed no significant difference in cancer incidence between the aspirin users and the placebo group. However, the aspirin users experienced an increased risk of metastasized or Stage 4-presenting cancers, including colorectal cancer. Additionally, they had a raised likelihood of cancer death from Stage 3-presenting cancers. The authors concluded that aspirin use “may accelerate the progression of cancer” in older adults.

Explaining Different Results

The ages of participants in the two investigations are not that different. “In the ACS study, the mean age was 64 in non-aspirin users and 76 in aspirin users. In the ASPREE trial the mean age was 70 years in non-aspirin users and 74  years in aspirin users,” Dr. Marco Scarpa, ACS study coordinator, told The Epoch Times in an email.

Since the ages are similar, the conclusions seem to somewhat contradict each other. However, the focuses differed, with the ACS study examining the earlier stages of cancer and the ASPREE trial looking at the later stages.

Dr. Scarpa said the ACS study investigated local surveillance mechanisms, so the participants were mostly in the early and locally advanced cancer stages. In contrast, the ASPREE trial investigated the effects of aspirin on overall survival.

The ACS study researchers speculated that immune surveillance mechanisms work better in the early phases of cancer. “Such mechanisms center on the messaging between cells lining the colon and cancer-fighting immune cells called T lymphocytes, which aspirin may enhance. In later stages, probably other cell types start to play a role, and this interaction that aspirin may enhance probably becomes secondary,” Dr. Scarpa said.

Cancer Progression in the Elderly

The 2020 review of the body of research on the use of aspirin as a cancer preventative acknowledged that the ASPREE trial was a significant contributor to the overall picture. It recognized that concerns about the use of aspirin in older adults bear consideration.

At this point, researchers are not certain of the underlying factors of why aspirin might accelerate cancer progression in the elderly, but they speculate they may stem from age-related changes in immunity.

“Maybe aspirin does have a different effect on people as they age,” ASPREE trial coauthor Dr. Leslie Ford said in a National Cancer Institute press release. “And, similar to what we’ve seen with COVID-19, does it affect the immune system differently in an older population than it does in a younger, healthier one with a stronger immune system? It’s definitely a plausible explanation.”

The ASPREE trial authors theorized that aspirin may inhibit anti-tumor immune or inflammatory responses that play a vital role in controlling cancer growth and spread in later stages. This effect may be particularly present in those with compromised immunity. Age is also associated with mutations and molecular changes in cancer genes of older adults.

Benefits Versus Risks

Because aspirin has risks, they must be weighed against the benefits for different individuals.

The ASPREE trial casts doubt on the cancer prevention effects of aspirin, at least in older adults, and aspirin links to a well-established increased risk of serious gastrointestinal bleeding, according to the ASPREE commentary. For these reasons, the authors do not recommend aspirin as a cancer preventative in people aged 70 and older.

Additionally, because research seems to be “missing a critical piece of the puzzle” in the biological effects of cancer in different ages, daily aspirin use should be further restricted, added the commentary authors.

“Aspirin use is best reserved for individuals with specific molecularly driven cancer risks, such as those with Lynch syndrome, in whom it has been shown to halve the risk of colorectal cancer, without serious bleeding risk, on extended follow-up,” they stated. Lynch syndrome is an inherited condition that causes a higher risk of cancer.

Despite the commentary’s conclusion, people should follow the advice of their oncologist, who will base recommendations on their individual health needs.

Mainstay of Cancer Prevention

The ASPREE commentary stated that the mainstay of cancer prevention in healthy individuals involves lifestyle changes and risk- and age-based screening. Recommended lifestyle changes include:

• Quitting smoking, if applicable
• Limiting the use of alcohol
• Maintaining an optimal weight
• Exercising regularly

It is worth noting that the above lifestyle changes are associated with other health benefits and have no potential for harm, unlike aspirin use.

Guidelines for colorectal cancer screening involve getting a regular colonoscopy between the ages of 45 and 75 for healthy people. This test shows noncancerous tumors called polyps, which can develop into cancer. Removing polyps larger than 1 centimeter may reduce the risk of cancer.