A recent study has added to the growing body of evidence linking daily aspirin use to a reduced risk of cancer. However, conflicting research suggests that aspirin may have the opposite effect in older individuals.
A study published in April in the Journal of the American Cancer Society (ACS) found that daily low-dose aspirin may lower the incidence and mortality rates of colorectal cancer. In contrast, a large 2020 clinical trial known as ASPREE, published in the Journal of the Natural Cancer Institute, indicated that aspirin could actually increase the incidence and mortality rates of cancer in older adults.
So, does this mean that aspirin may be beneficial for preventing cancer in some age groups but not in others? The answer is: possibly.
The ACS study’s findings align with several other studies that suggest aspirin’s positive effects in fighting colorectal cancer. However, the ASPREE trial, due to its large size and compelling results, cannot be dismissed. A research commentary on the ASPREE trial concluded that daily aspirin use may be suitable only for individuals at a higher risk of cancer.
Aspirin May Enhance Immunity in Cancer
The ACS study conducted at the University of Padoa (UP) in Italy examined 238 individuals diagnosed with colorectal cancer who underwent surgery between 2015 and 2019. Among them, 12% were regular aspirin users. The study found that aspirin users exhibited:
- Less cancer spread to lymph nodes
- Higher levels of tumor-infiltrating lymphocytes (cells that combat cancer)
- Increased CD80 protein in colorectal cells
- Increased CD80 protein in healthy tissue surrounding the cancer
In a press release from UP, the authors explained the significance of the elevated CD80 protein. In cancer cells, it seems to enhance the ability to communicate with 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 the latest piece of evidence supporting the value of aspirin in preventing colorectal cancer. A 2020 review stated that “meta-analyses and other systematic reviews of large observational cohort studies have estimated that aspirin reduces the risk of colorectal neoplasia by approximately 20–30%.”
Aspirin May Accelerate Cancer Progression
Clinical trials investigating aspirin as a cancer preventative have mainly focused on younger individuals, as noted by the ASPREE trial. To explore the effects of aspirin use in older adults, the trial followed 19,114 healthy individuals aged 70 and older for a median of 4.7 years, with a daily dose of 100 milligrams of aspirin. Despite the seemingly conclusive nature of the ACS study and previous research findings, the ASPREE trial results warrant close examination.
The results indicated no significant difference in cancer incidence between aspirin users and the placebo group. However, aspirin users showed an increased risk of metastasized or stage 4-presenting cancers, including colorectal cancer. They also had a higher 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 the Discrepancy
The ages of participants in the two studies are relatively similar. “In the ACS study, the mean age was 64 for non-aspirin users and 76 for aspirin users. In the ASPREE trial, the mean age was 70 for non-aspirin users and 74 for aspirin users,” explained Dr. Marco Scarpa, the ACS study coordinator, in an email to The Epoch Times.
Despite the similar ages, the conclusions seem to contradict each other. However, the focus of the studies differed, with the ACS study examining early cancer stages and the ASPREE trial investigating later stages.
Dr. Scarpa suggested that the ACS study explored local surveillance mechanisms, thus enrolling participants mostly in the early and locally advanced cancer stages. In contrast, the ASPREE trial looked at the overall survival effects of aspirin.
