ATLANTA — A large new observational study published Friday found more evidence of an association between daily aspirin use and modestly lower cancer mortality, but suggested any reduction may be smaller than that observed in a recent analysis. The study appeared online in the Journal of the National Cancer Institute.
A recent analysis pooling results from existing randomized trials of daily aspirin for prevention of vascular events found an estimated 37% reduction in cancer mortality among those using aspirin for five years or more. But uncertainty remains about how much daily aspirin use may lower cancer mortality, as the size of this pooled analysis was limited and two very large randomized trials of aspirin taken every other day found no effect on overall cancer mortality, the authors of the latest study reported.
For the current study, American Cancer Society researchers led by Eric Jacobs analyzed information from 100,139 predominantly elderly participants in the Cancer Prevention Study II Nutrition Cohort who reported aspirin use on questionnaires, did not have cancer at the start of the study and were followed for up to 11 years. They found daily aspirin use was associated with an estimated 16% lower overall risk of cancer mortality, both among people who reported taking aspirin daily for at least five years and among those who reported shorter term daily use. The lower overall cancer mortality was driven by about 40% lower mortality from cancers of the gastrointestinal tract (e.g., esophageal, stomach and colorectal cancer) and about 12% lower mortality from cancers outside the gastrointestinal tract.
The authors noted that their study was observational, not randomized, and therefore could have underestimated or overestimated potential effects on cancer mortality if participants who took aspirin daily had different underlying risk factors for fatal cancer than those who did not. However, the study's large size is a strength in determining how much daily aspirin use might lower cancer mortality.
"Expert committees that develop clinical guidelines will consider the totality of evidence about aspirin's risks and benefits when guidelines for aspirin use are next updated," Jacobs said. "Although recent evidence about aspirin use and cancer is encouraging, it is still premature to recommend people start taking aspirin specifically to prevent cancer. Even low-dose aspirin can substantially increase the risk of serious gastrointestinal bleeding. Decisions about aspirin use should be made by balancing the risks against the benefits in the context of each individual's medical history. Any decision about daily aspirin use should be made only in consultation with a healthcare professional."