Regular low doses of aspirin for at least six years was associated with a modestly reduced overall risk for cancer, primarily due to a lower risk for gastrointestinal tract cancer, especially colorectal cancers, according to an article published online by JAMA Oncology.

The US Preventive Services Task Force recently recommended aspirin to prevent colorectal cancer and cardiovascular disease among many US adults.

However, the association of aspirin on the risk of other types of cancer and what additional effect aspirin might have in the context of screening remain unclear.

Andrew T. Chan, M.D., M.P.H., of the Massachusetts General Hospital, Boston, and coauthors looked at the association of aspirin with cancer among 135,965 women and men enrolled in two large US studies of health care professionals.

The authors documented 20,414 cancers among 88,084 women and 7,571 cancers among 47,881 men during a 32-year follow-up.

Regular use of aspirin two times or more per week was associated with a 3 percent lower risk for overall cancers, which was mostly due to a 15 percent lower risk for gastrointestinal tract cancers and a 19 percent lower risk for cancers of the colon and rectum, according to the results.

However, regular use of aspirin was not associated with a lower risk for other major cancers, such as breast, prostate or lung, the authors report.

Study findings suggest that, for the gastrointestinal tract, aspirin may influence additional mechanisms important for the formation of cancer, which may explain the stronger association of aspirin for a lower risk of gastrointestinal cancers.

On a population-wide level, the authors suggest regular aspirin use could prevent 17 percent of colorectal cancers among those who did not undergo lower endoscopy and 8.5 percent of colorectal cancers among those who underwent lower endoscopy.

Limitations to the study include that results of an observational study, such as this, are not as definitive as those of a randomised clinical trial.

"Aspirin may be a potential low-cost alternative to endoscopic CRC [colorectal cancer] screening in resource-limited settings or a complement in settings in which such programme are already implemented, including the general US population, in whom screening adherence remains suboptimal," the study concludes.

Source: JAMA Network