Regular aspirin use may substantially lower a person's risk of developing cancer of the pancreas, according to a report in the Journal of the National Cancer Institute (JNCI: Vol. 94, No. 15: 1168-1171).

"Aspirin use on a regular basis seemed to cut risk of pancreatic cancer in half," said study co-author Aaron R. Folsom, MD, at the University of Minnesota School of Public Health, in Minneapolis.

But that doesn't mean everyone should take the drug regularly without talking with a doctor, because regular use of the drug can cause have serious side effects, said Folsom.

The researchers found the protection against pancreatic cancer from aspirin while looking at data from the Iowa Women's Health Study. In this study, 40,000 women between the ages of 55 and 69 filled out questionnaires in 1986. They provided information about their health habits and agreed to respond to updated questionnaires later.

At the start of this study, the researchers eliminated those with cancer, those who didn't provide enough information, or those who died before 1992, leaving the scientists with data from about 28,000 women.

Beginning in 1992, these women were asked about their aspirin use, along with other health issues. They were asked again in 1997, and were followed through the end of 1999.

Those taking aspirin six or more times per week were 60% less likely to develop pancreatic cancer than women who never used aspirin.

Those who used it two to five times per week were about half as likely to develop the disease as those who never used it.

And women who took aspirin once a week or less had about 25% less chance of developing it as those who never used it.

The researchers did not study the dose of aspirin taken, the length of time it was used, or the reason the women were using it.

Aspirin is a non-steroidal anti-inflammatory drug, or NSAID. Several other NSAIDs, such as ibuprofen, are available, but none of these other NSAIDs affected pancreatic cancer risk in the study.

Aspirin has also been shown to protect against heart disease and may lower the risk of colon cancer, according to earlier reports.

However, the way aspirin works means it carries risks as well as benefits if used regularly instead of occasionally.

Aspirin lowers body production of an enzyme called COX-2. That enzyme causes inflammation that can damage cells and may also fuel cancer cell growth, so lowering it is a good thing.

But because aspirin also lowers levels of COX-1, crucial to integrity of the body's smallest blood vessels, regular use of it can cause bleeding in the stomach or intestines, which have many tiny vessels.

So doctors carefully weigh an individual's potential risks and benefits before advising aspirin regularly.

Newer versions of NSAIDs that cut production of COX-2 only weren't widely available during the years of the study, so the researchers did not look at these.

"This is one of a few studies that have looked at the relationship between NSAIDs and pancreatic cancer, and several have come to conflicting conclusions, so more study is needed," said Jeanne Calle, PhD, director of analytic epidemiology for the ACS.

"The results would have been stronger if some effect had also been seen for other non-aspirin NSAIDs," Calle said.

Folsom suggested in his report that more clinical trials are needed to look at the type of drug used, the length of time it is taken, and the amount of the drug taken to determine whether or not aspirin should be used as a chemopreventive agent in the future.