Aspirin Use May Not Protect Older Adults Against Colorectal Cancer

Aspirin use may not have a protective factor against colorectal cancer (CRC) in older adults, and can even come with possible risks, according to recent study results published in JAMA Oncology. These findings go against previous recommendations to use aspirin to prevent the disease.

“Substantial evidence suggests that a benefit of aspirin for CRC requires at least five to 10 years of use,” the study authors wrote. “However, these data are primarily delivered from cohort studies and (randomized clinical trials) conducted in middle-aged adults.”

Currently, the United States Preventive Services Task Force (USPSTF) recommends that individuals between the ages of 50 and 59 with a greater than 10% 10-year cardiovascular risk take aspirin to help prevent CRC. However, data is far more limited when it comes to older adults.

Older Age May Negate Aspirin’s Protective Benefits

The study authors reviewed data from the two largest cohort studies in the U.S.: the Nurses’ Health Study and the Health Professionals Follow-up study. They looked at 94,540 participants (all aged 70 or older) over the years that the studies were conducted (1980-2014 and 1986-2014). Overall, there were 1,431 cases of CRC.

Patients who started aspirin use before the age of 70 had a significantly lower rate of CRC than those who did not have regular aspirin use. However, those who started regular aspirin use at 70 or older did not see that benefit. The results counted for other factors, such as cholesterol-lowering drugs, hyperlipidemia, hypertension, and CVD.

“The apparent protective benefits of aspirin use at or after 70 years were evident only among those who had regularly used aspirin for five or more years before 70 years of age,” the authors wrote. “In contrast, no benefit was observed among those who used aspirin for less than five years before 70 years of age.”

CRC in older adults may have a different molecular makeup than it does in younger adults, which is one possible explanation why aspirin only benefitted people who took it before the age of 70.

“There is growing evidence that cancers that arise in older adults may have a differential mechanistic basis compared with those in younger individuals,” they wrote. “For example, aging is associated with alteration in DNA methylation, which may affect susceptibility to cancer.”

Aspirin May Pose Risks

Additionally, the authors cited findings from another trial – the Japanese Primary Prevention Project (JPP), which involved individuals between the ages of 60 and 85 years – which showed that a low-dose aspirin regimen was associated with higher cancer incidence, but not cancer-related death.

Another randomized clinical trial called ASPREE also showed that at the 4.7-year follow-up period, participants taking aspirin had a higher all-cause mortality rate, with many of the deaths being associated with cancer.

“Because 89% of the participants in the ASPREE trial and all the participants in the JPP study did not regularly use aspirin before enrollment, our results demonstrating that initiation of aspirin use at or after age 70 was not associated with a reduction in risk of incident CRC are broadly consistent with the lack of protective effect observed in ASPREE and JPP,” the researchers wrote.

Ultimately, the authors concluded that there should be more studies to better understand the biologic mechanisms of aspirin and its relationship to CRC. In the meantime, they recommend patients talk to their health care team about the risks and benefits of regular use.

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