Many things are capable of increasing our cancer risk, including obesity, smoking, and excessive drinking. Lowering that risk, however, can be more difficult. Regular screenings can help, but according to two major, long-term epidemiologic studies, the use of aspirin may complement the preventative benefits of colonoscopy and other cancer screening tests.

“We now can recommend that many individuals consider taking aspirin to reduce their risk of colorectal cancer — particularly those with other reasons for regular use, such as heart disease prevention — but we are not at a point where we can make a general recommendation for overall cancer prevention,” said Dr. Andrew Chan, chief of the Clinical and Translational Epidemiology Unit in the Massachusetts General Hospital Division of Gastroenterology and senior author of the report, in a press release.

“Our findings imply that aspirin use would be expected to prevent a significant number of colorectal cancers above and beyond those that would be prevented by screening and may have even greater benefit in settings in which the resources to devote to cancer screening are lacking.”

Thirty-two years’ worth of data from almost 136,000 patients helped researchers reach this conclusion. A large number of studies had already supported the regular use of aspirin for prevention of colorectal cancer, but aspirin’s effect on overall cancer risk has been a little less clear. The new study found that while regular aspirin use (defined as taking a standard or low-dose aspirin tablet at least twice a week) reduced the risk of colorectal cancer by 19 percent, it only reduced the absolute risk of any type of cancer by 3 percent. No reduction at all was seen for lung, prostate, or breast cancer risk.

The beneficial effects of aspirin in terms of colorectal cancer risk cropped up after five years of continuous use at doses ranging from half a tablet a week to one low-dose tablet every day. Benefits related to other gastrointestinal tumors, which aspirin reduced risk of by 15 percent, appeared after six years at the same dosage level.

The report suggests regular aspirin use could prevent almost 30,000 gastrointestinal tract tumors in the U.S. every year, and could prevent an additional 7,500 colorectal tumors in U.S. adults over 50 who undergo endoscopic screening. It could even, they predict, prevent 9,800 new cases among the almost 30 million adults who are not screened.

“At this point, it would be very reasonable for individuals to discuss with their physicians the advisability of taking aspirin to prevent gastrointestinal cancer, particularly if they have risk factors such as a family history,” Chan said. “But this should be done with the caveat that patients be well informed about the potential side effects of regular aspirin treatment and continue their regular screening tests. Furthermore, aspirin should not be viewed as a substitute for colonoscopy or other cancer screening tests.”

Source: Cao Y, Nishihara R, Ogino S, Fuchs C, Wu K, Wang M, et al. regular Aspiring Use Found To protect Against Overall Cancer Risk. JAMA Oncology. 2016.