New evidence has shown that aspirin has a potential role in reducing the risk of cancer death—which could mean that clinical guidelines for the use of aspirin in preventive care might someday include cancer prevention, according to the results of a review published early online in Nature Reviews Clinical Oncology.
The current clinical guidelines for the use of aspirin in disease prevention consider only its cardiovascular benefits, weighed against the potential harm from aspirin-induced bleeding. In previous studies, daily aspirin use has been shown to reduce the risk of colorectal cancer and the recurrence of polyps; however, these benefits have not outweighed the potential harm from aspirin-induced bleeding.
Now, recently published secondary analyses of cardiovascular trials indicate that aspirin may have a viable role in cancer prevention. The data provides the first randomized evidence that daily aspirin use may also reduce the incidence of all cancers combined, even at low doses (75–100 mg daily). In fact, the evidence suggests that a daily dose of aspirin (75mg or more) might lower overall cancer incidence and overall cancer mortality.
The review included six primary prevention trials in which patients were randomized to daily low-dose aspirin treatment. The results indicated an approximately 20 percent reduction in overall cancer incidence between three and five years after initiation of aspirin use and a 30 percent reduction during follow-up more than five years later. Follow up that occurred more than five years after initiation of aspirin use indicated that cancer mortality was also reduced. The observed benefit did not increase with aspirin doses above 75-100mg.
Notably, the data from this review excluded results from the Women’s Health Study (WHS), a 10-year trial in which women took 100mg of aspirin ever other day and which reported no reduction in cancer incidence or mortality.
Researchers continue to study the risks and benefits of daily aspirin use, but it appears that evidence is mounting that aspirin may have a valid preventive role in cancer. The researchers noted that even a 10 percent reduction in overall cancer incidence during the first 10 years of aspirin treatment could affect the risk-benefit balance—meaning the benefits of aspirin could outweigh the risks in average-risk populations. Stay tuned—as evidence accumulates, the clinical guidelines for the preventive use of aspirin could change to include cancer prevention.
 Thun MJ, Jacobs EJ, Patrono C. The role of aspirin in cancer prevention. Nature Reviews Clinical Oncology. Published early online April 3, 2012. doi:10.1038/nrclinonc.2011.199