Researchers from the American Cancer Society have found that taking aspirin neither increases a person's risk of dying from pancreatic cancer, nor decreases it.

Their study, published in the latest issue of the Journal of the National Cancer Institute (Vol. 96, No. 7: 524-528), is the largest yet to examine the relationship between the common painkiller and pancreatic cancer, the fourth leading cause of cancer death in the US.

The finding could provide some reassurance to people who take aspirin regularly, said lead author Eric Jacobs, PhD, a senior epidemiologist with ACS.

"[Our] results … do not support an important effect of aspirin use on pancreatic cancer mortality," he said. Because pancreatic cancer is almost always fatal, the results would most likely be the same for incidence of pancreatic cancer, he noted.

Previous research on the issue has yielded mixed results. The Iowa Women's Health Study, for instance, found that women who used aspirin frequently had a lower risk of pancreatic cancer than women who didn't use aspirin. But more recently, the Nurses' Health Study found that women who were long-term aspirin users or who took 2 or more pills per week had a greater risk of developing the disease.

Although both of those studies included substantial numbers of women (28,000 and 88,000, respectively), Jacobs noted that the ACS study included many more people than either of them.

He and his colleagues studied 987,590 men and women for 18 years. The participants were asked about their aspirin use and about other factors that could influence their risk of pancreatic cancer, such as having diabetes, smoking, and being overweight or obese. During the course of the study, 4,577 people died of pancreatic cancer.

The researchers found no associations between aspirin use and pancreatic cancer, even after taking the other risk factors into account. People who used aspirin daily were no more or less likely to die of pancreatic cancer than those who used it only occasionally or those who never used it. The results were the same for both men and women.

The study did not examine the dose of aspirin each person took, just how often it was taken.

Millions of Americans take aspirin daily because it is proven to reduce the risk of heart disease. Many studies also suggest aspirin can reduce the risk of colon cancer and possibly some other cancers. But there are currently no recommendations to use aspirin to ward off cancer of any type.

"The American Cancer Society does not recommend aspirin use for cancer prevention, and these findings will not affect our recommendations," Jacobs said.

Because aspirin use can lead to serious side effects like stomach bleeding, it is wise to consult a doctor before beginning any aspirin regimen.

About 31,270 people in the United States are expected to get pancreatic cancer this year, according to ACS estimates, and most of them will die from it. Survival is poor because the disease is very hard to detect in its early stages. Tumors in the pancreas cannot be seen or felt during routine physical examinations, and there are no reliable screening tests. Patients rarely have any symptoms until the tumor has grown fairly large or spread to other organs.

Experts say exercising, eating right, and not smoking are ways people can reduce their risk of developing pancreatic cancer.