Boston—Regular use of aspirin appears to significantly reduce the overall risk of cancer, especially colorectal cancer and other tumors of the gastrointestinal tract, according to an analysis of data from two major, long-term epidemiologic studies.
The study, published online recently by JAMA Oncology, calls for the use of aspirin to complement, but not replace, the preventive benefits of colonoscopy and other methods of cancer screening.

“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,” emphasized senior author Andrew Chan, MD, MPH, of Massachusetts General Hospital (MGH). “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.”

While many studies have found evidence that regular aspirin use helps prevent colorectal cancer, aspirin's effects on overall cancer risk has not been clear.

In light of that, the research team analyzed data collected over 32 years from nearly 136,000 participants in the Nurses’ Health Study and the Health Professionals Follow-up Study. Results indicate that participants who reported regular aspirin use—taking either a standard or a low-dose aspirin tablet at least twice a week—had a 3% absolute lower risk of any type of cancer compared to those not reporting regular aspirin use. At the same time, regular aspirin use was found to reduce the risk of colorectal cancer by 19% and the risk of any gastrointestinal cancer by 15%, although no significant reduction was identified for the risk of breast, prostate, or lung cancer.

The study notes that aspirin’s protective benefit appeared after 5 years of continuous use at dosages ranging from 0.5 to 1.5 standard tablets a week or one low-dose tablet a day.

The researchers estimate that regular aspirin use could prevent close to 30,000 gastrointestinal tract tumors in the United States each year as well as an additional 7,500 colorectal tumors among U.S. adults over 50 who have endoscopic screening and 9,800 among the almost 30 million 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 in an MGH press release. “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.”

A commentary recommends some caution until completion of further research, however.

“To reflect accurately the often complex, real-world clinical scenarios in which physicians and patients contemplate the use of aspirin, any truly informative analysis of its use must weigh its cumulative benefits against its cumulative risks,” write Eduardo Vilar, MD, PhD, Karen Colbert Maresso, MPH, and Ernest T. Hawk, MD, MPH, of the University of Texas MD Anderson Cancer Center in Houston.

Until further research is available, the commentary states, “learning that aspirin’s preventive effects on GI tract cancer seem to extend even to those individuals who undergo CRC screening provides further support for aspirin’s possible future use as a cancer-preventive agent.”

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