Is it time to recommend aspirin for cancer prevention? “It’s the question we are asking,” said Andrew T. Chan, MD, Massachusetts General Hospital and Harvard Medical School, who wrote a commentary accompanying three new studies in The Lancet and Lancet Oncology. The studies, by Peter M. Rothwell, MD, of Oxford University, and colleagues, add new data to suggest that daily aspirin reduces the risk of colorectal cancer and other malignancies, including distant metastases (see article).

The evidence in favor of aspirin is compelling, Dr. Chan said in an interview, but there are still some notable barriers to recommending it in the general population. One of these is the lack of supporting evidence, so far, from the Women’s Health Study and the Physicians’ Health Study. With tens of thousands of participants who have been followed for more than a decade, these are the largest primary prevention studies to have included cancer incidence as a prespecified endpoint. Their findings have shown that aspirin is associated with a reduced risk of cardiovascular disease, but not colorectal cancer or overall cancer. Longer-term analyses of these data continue.

Neither the Women’s Health Study nor the Physicians’ Health Study was included in The Lancet analyses, because their participants took aspirin on alternate days rather than every day. That makes them outlier studies, Dr. Chan said, “but important outlier studies.”

Individualize Recommendations

The other major obstacle to population recommendations for regular aspirin use is the risk of bleeding, a sometimes serious, occasionally even fatal, side effect.

“I don’t think we can make a population recommendation until there is a more formal assessment of the risks and benefits that also accounts for the limitations of the data at hand,” Dr. Chan said. “Based on the current state of the evidence, it remains prudent to individualize recommendations.”

Most important, there needs to be a discussion by doctors and patients of possible benefits and possible risks, and that discussion needs to include both cancer and cardiovascular disease, he said. “It’s very difficult for physicians and patients to discuss aspirin for each disease in isolation.” ■

Disclosure: Dr. Chan previously served as a consultant to Bayer Healthcare and Millennium Pharmaceuticals.