Study: Aspirin Reduces Cancer Risk

The largest and longest study of long-term, regular aspirin use finds that the drug may lead to a modestly reduced risk for some types of gastrointestinal cancers.

Regularly taking aspirin for years may protect users people from some types of gastrointestinal (GI) cancers, especially colorectal cancer, according to Harvard researchers presenting their work yesterday (April 19) at the annual American Association for Cancer Research (AACR) meeting being held in Philadelphia. But long-term aspirin use may also come with an elevated risk of adverse effects, such as GI bleeding, cautioned Yin Cao, a research fellow at the Harvard School of Public Health who coauthored the study. “You need to consider the risk of [prolonged aspirin use],” Cao told The Scientist during an AACR poster session where she presented the work.“Previous studies of aspirin and cancer have been limited in terms of their size, length of follow-up, or ability to examine aspirin use in the context of other lifestyle factors,” she said in a statement. “Our research provides critical information regarding the full constellation of potential benefits of aspirin use, at a range of doses, timing, and duration of use, within a large population of individuals.”

Cao and her colleagues considered data collected from more than 100,000 men and women who had enrolled in separate studies in the 1980s. The researchers found an overall 5 percent decreased risk for all cancers in people who reported taking two or more aspirin tablets per week. This decrease was driven mostly by a 20 percent reduction in risk for GI cancers (including a 25 percent drop in colorectal cancer risk). There were no reductions in risk for breast, advanced prostate, lung, or other non-GI cancers associated with aspirin use, Cao added.Other studies had collected data on cancer in relation to aspirin use, but the Harvard study followed more people for longer (up to 32 years). Cao and her colleagues showed that significant risk reductions for developing cancer came only after 16 years of using the drug, and the effects dissipated four years after discontinuing aspirin use. “Dose and duration both help,” Cao said.She added that her team, which includes Andrew Chan of Harvard Medical School, is now working to genetically characterize subsets of patients who may show an enhanced response to long-term, regular aspirin use with regard to cancer.

Chan, who has previously served as a consultant for Bayer Healthcare, Pfizer, and Pozen, is today (April 20) presenting on some of the ways the team is researching the mechanisms behind aspirin’s apparent effects on cancer risk reduction.