LONDON - A new report from British scientists suggests that long-term, daily aspirin use may modestly lower the risk of dying of certain cancers, though experts warn the study isn't strong enough to recommend that healthy people start taking a pill that can cause bleeding and other problems.
In a new observational analysis published online today in the medical journal Lancet, Peter Rothwell of Oxford University and colleagues looked at eight trials that included more than 25,000 patients and cut the risk of death from certain cancers by 20 percent.
While some experts said the analysis adds to evidence of aspirin's potential to cut cancer risk, others said it falls short of changing advice to healthy people, and it failed to show the benefits apply equally to women.
The trials mostly compared men who took a daily dose of at least 75 milligrams of aspirin for heart problems with people who took a placebo or another drug. On average, the studies lasted at least four years.
Researchers used national cancer registries to get information on participants after the studies ended, though they weren't sure how many aspirin takers continued using it or how many people in the comparison groups may have started.
The researchers said that the projected risk after two decades of dying from cancers like lung and prostate would be 20 percent lower in groups who had taken aspirin and 35 percent lower for gastrointestinal cancers like colon cancer.
These odds are figured from smaller numbers; there were 326 lung cancer deaths in all, for example. Only one-third of people in the analysis were women, not enough to calculate any estimates for breast cancer. There appeared to be no benefit to taking more than 75 milligrams daily.
The analysis excluded a high-quality experiment that tested aspirin every other day in nearly 40,000 U.S. women. In that trial, no reduction in cancer risk was seen except for lung cancer deaths.
No funding was provided for the new Lancet analysis but several of the authors have been paid for work for companies that make aspirin and similar drugs.
Scientists said it would take some time to digest the study results and figure out which people should take aspirin.
Eric Jacobs, an American Cancer Society epidemiologist, called it a "major contribution" and said the study results, in addition to previous research, suggested aspirin's effects on the risk of dying from several cancers "appear likely."