Published on January 28, 2021
Research Shows Low-Dose Aspirin May Reduce Risk in Some Cancers
Aspirin has been shown to relieve pain, reduce fevers and prevent a heart attack or stroke. It turns out it may have protective benefits against some cancers, too.
A National Cancer Institute (NCI) study found that taking aspirin at least three times a week reduced the risk of death among older patients with bladder and breast cancer. The findings were reported earlier this month in JAMA Network Open.
NCI researchers studied data from 139,896 individuals age 65 years or older from the NCI’s Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) Screening Trial. The trial was designed to determine the effects of screening on cancer-related mortality in men and women ages 55 to 74. Of the group studied, 5.4% had bladder cancer, 14.0% had breast cancer, 1.0% had esophageal cancer, 1.2% had gastric cancer, 2.7% had pancreatic cancer and 2.2% had uterine cancer (other cancers were excluded).
Taking aspirin at least three times a week was associated with a 33% and 25% reduced risk of mortality among older patients with bladder and breast cancer, respectively. Any aspirin use was significantly associated with a 25% and 21% reduced risk. The team found no survival benefit among older patients with esophageal, gastric, pancreatic or uterine cancer taking aspirin.
Aspirin’s Cancer Benefits
Studies on the benefits of taking low-dose aspirin (81 mg) to prevent or treat cancer are inconsistent and inconclusive. A 2016 study by Harvard researchers found that taking either a 325 mg tablet or an 81 mg tablet two or more times per week was associated with a 3% reduction in cancers overall. However, they saw no effect on major cancers including those of the breast, prostate or lung.
The Aspirin in Reducing Events in the Elderly (ASPREE) study of adults age 70 and older found that those who took 100 mg of aspirin daily had a nearly 20% higher risk of being diagnosed with advanced cancer and a 30% higher risk of dying from it.
This also included colorectal cancer, even though most studies have linked aspirin use to a decreased risk for being diagnosed with or dying from colorectal cancer — so much so that in 2016, the US Preventive Services Task Force (USPSTF) recommended certain people take daily low-dose aspirin to reduce their risk of heart disease and colorectal cancer. Participants in the aspirin group of the ASPREE study had a 77% higher risk of dying from colorectal cancer than those in the placebo group.
Breast Cancer and Aspirin
In terms of breast cancer, a 2017 study that followed 57,000 women found that taking low-dose aspirin at least three times a week was linked to a 20% risk reduction for HR+, HER2- breast cancer. Overall, regular baby aspirin use reduced the risk of breast cancer by 16%. That reduction was not seen with regular-dose aspirin or other non-steroidal anti-inflammatory drugs such as ibuprofen or acetaminophen.
Another analysis that reviewed the findings of 13 previous studies (more than 850,000 women) found a 14% lower risk of developing breast cancer after five years of taking aspirin, a 27% lower risk after 10 years of aspirin use and a 46% reduction in risk after 20 years of aspirin use.
While the studies didn’t establish a clear cause-and-effect relationship, researchers speculate that aspirin’s role as an aromatase inhibitor provides a protective benefit. Aromatase inhibitors lower estrogen levels in postmenopausal women; that means that less estrogen is available to fuel the growth of HR+ breast cancer cells.
The Bottom Line
“It’s too soon to suggest that women should take aspirin to prevent breast cancer,” wrote Dr. Robert H. Shmerling, senior faculty editor for Harvard Health Publishing, in a blog post about aspirin and breast cancer risk. While studies show a link between aspirin use and reduced breast cancer risk, they cannot prove that aspirin caused the risk reduction. Dr. Shmerling added that while aspirin is generally considered safe, it can cause gastrointestinal ulcers, bleeding and allergic reactions.
Still, the results of the JAMA Network Open study add to the accumulating evidence that aspirin may improve survival for some cancers.
“Although prior research has been most heavily concentrated in gastrointestinal cancers, our analysis extends the advantages associated with aspirin use to other cancers, such as bladder and breast cancers,” the authors wrote. “However, although aspirin use may confer a cancer-protective effect, it remains necessary to consider the harms, as well as the benefits, of long-term aspirin use.”
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