Long-term, regular aspirin use was associated with a modestly reduced overall risk for cancer driven primarily by a reduction in the risk for colorectal cancers, according to research presented at the AACR Annual Meeting 2015, April 18-22.

“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. 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,” said Yin Cao, MPH, ScD, a research fellow in the Department of Nutrition at Harvard School of Public Health in Boston.

In this prospective study, Cao and colleagues collected data on aspirin use, cancer diagnoses, and other risk factors from 82,600 women from the Nurses’ Health Study and 47,651 men from the Health Professionals Follow-up Study.

After 32 years of follow-up, 27,985 incident cancers were documented.

Study participants who reported consuming two or more aspirin tablets per week had a five percent decreased risk for overall cancer.

This decrease in risk was driven mainly by a 20 percent reduction in gastrointestinal cancers, including a 25 percent reduction in colorectal cancers and a 14 percent reduction in gastroesophageal cancers.

Long-term, regular aspirin use and increased doses of aspirin appeared to drive the reduced risk of cancer.

Significant risk reduction was seen only after 16 years of aspirin use and was no longer evident within four years of discontinuing use.

The researchers found no association between regular aspirin use and a decreased risk for nongastrointestinal cancers, specifically, breast, lung, or prostate cancers.

Senior study author Andrew T. Chan, MD, MPH, associate professor in the Department of Medicine at Harvard Medical School and director of the Gastroenterology Training Program at Massachusetts General Hospital, who will be presenting a plenary talk titled “Molecular risk stratification for aspirin chemoprevention,” Monday, April 20, 8:45 a.m., said, “Aspirin has been shown to be effective in the prevention of heart attacks and strokes, particularly among individuals who have had a prior history of these cardiovascular events. However, recent findings suggest that such benefits may not be as pronounced for individuals who are at low risk for heart attacks or strokes. Thus, our findings suggest that for many individuals the potential benefits of aspirin for the prevention of cancer may actually merit greater consideration than prevention of cardiovascular events. This strengthens the case for further research into defining subsets of the population that may obtain preferential benefit from regular aspirin use. As an example of this strategy, we recently showed that an individual’s genetic background might influence the apparent reduction in risk of colorectal cancer associated with aspirin use.”

Cao cautioned that despite these results, it is premature to recommend general use of aspirin for cancer prevention.

“Individuals, in consultation with their physicians, need to consider the potential risks of taking aspirin, including gastrointestinal bleeding,” Dr. Cao said. “The results of ongoing research to develop more tailored treatment based upon a personalised assessment of risks and benefits will be critical before recommending aspirin for chemoprevention of cancer.”

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Source: AACR