​​Aspirin May Reduce Risk for Pancreatic Cancer

In a new study, researchers found that regular use of aspirin was associated with an almost 50 percent reduction in pancreatic cancer risk.

Patients diagnosed with pancreatic cancer have a grim prognosis: Fewer than 8 percent survive five or more years after diagnosis, according to statistics from the National Cancer Institute.

Given the poor outlook, it is crucial that we find ways to prevent pancreatic cancer, says Harvey A. Risch, MD, PhD, professor of epidemiology in the Department of Chronic Disease Epidemiology at the Yale School of Public Health, Yale School of Medicine, and Yale Cancer Center in New Haven, Connecticut.

Dr. Risch is the senior author on a study  showing that regular use of aspirin by people living in Shanghai, China, was associated with decreased risk for developing pancreatic cancer. The study was published recently in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

"We found that regular use of aspirin by a large group of people in Shanghai cut risk of pancreatic cancer almost in half," said Dr. Risch.

This is consistent with what has been seen in other populations around the world, he says.

"Pancreatic cancer is relatively rare—just 1.5 percent of U.S. adults will be diagnosed with it at some point during life—and regular aspirin use can cause appreciable complications for some," explained Dr. Risch. "Therefore, a person should consult his or her doctor about aspirin use. Nevertheless, the balance of evidence shows that people who use aspirin to reduce risk for cardiovascular disease or colorectal cancer can feel positive that their use likely also lowers their risk for pancreatic cancer."

Dr. Risch and his colleagues recruited to the study patients newly diagnosed with pancreatic cancer at 37 Shanghai hospitals from December 2006 to January 2011. They also randomly selected controls from the Shanghai Residents Registry. The 761 patients with pancreatic cancer and 794 controls were interviewed in person to determine when they started using aspirin, the number of years they used aspirin, and when they stopped using aspirin, among other things. Almost all aspirin users used aspirin daily.

Among the patients with pancreatic cancer, 11 percent reported regular use of aspirin. Eighteen percent of the controls reported regular use of aspirin.

After adjusting for a number of factors, including body mass index, smoking history, and history of diabetes, the researchers found that ever having used aspirin regularly was associated with a 46 percent decreased risk for pancreatic cancer. Risk decreased by 8 percent for each year of aspirin use.

In reviewing the literature, Dr. Risch and his colleagues found 18 other studies that had investigated aspirin use and pancreatic cancer risk. Meta-analysis of the data from these studies showed that if the studies were considered by the year at which the mid-point of when the aspirin exposures were ascertained in the study, the odds ratios for regular use of aspirin and pancreatic cancer risk significantly decreased by 2.3 percent per year through the present.

According to Dr. Risch, the main limitation of the Shanghai study is that it is a case-control study that relied on participants accurately reporting past aspirin use.

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