Millions of people take aspirin for pain relief or to help prevent heart attacks. Aspirin has complex effects in the body, however, not merely reducing pain and fever and decreasing the tendency of blood to clot. In recent years, in fact, there has been growing interest in aspirin’s potential as an anti-cancer drug. Two new studies have added to the evidence.
First, a large study from American Cancer Society researchers, published in the Journal of the National Cancer Institute, found that daily aspirin users were 16 percent less likely to die from cancer over a five-year period than non-users. That’s much less than the 37 percent reduction seen in a 2011 analysis of eight clinical trials, but still substantial. In absolute terms, aspirin would prevent about 100 cancer deaths a year per 100,000 men and 40 cancer deaths per 100,000 women.
About 85 percent of the daily aspirin users reported taking just one tablet per day, mostly low-dose aspirin (81 milligrams). That strongly suggests they were taking aspirin for cardiovascular prevention rather than pain relief.
The study couldn’t differentiate the effects of aspirin on specific cancers, though the biggest effect seemed to be on gastrointestinal cancers, which would go along with previous research findings.
According to the accompanying editorial by John Baron, M.D., of the University of North Carolina School of Medicine in Chapel Hill, these findings are likely to underestimate the potential benefit, and “the big picture on aspirin use and cancer is very positive.”
The second study, published in the Journal of Clinical Oncology, involved data from a large national registry of men with biopsy-proven prostate cancer. Over a six-year period, the men who were taking aspirin, for whatever reason, were less likely to have a recurrence than non-users and less than half as likely to die from prostate cancer. Much information was lacking in the study, however. Notably, it did not look at dosage, duration or timing of aspirin use.
Keep in mind that these were both observational studies—not randomized, controlled clinical trials. What’s more, they were not designed to look specifically at aspirin’s effect on cancer, and that can complicate the interpretation of the results.
Many doctors rightly hesitate to recommend low-dose aspirin for healthy people because the small risk of stomach or intestinal bleeding, ulcers, and hemorrhagic (“bleeding”) strokes at least partly offsets the heart benefits. But adding in aspirin’s anti-cancer potential may well tip the balance in favor of benefits for many people, especially if aspirin is started in middle age.