Aspirin use linked to pancreatic cancer.

In a finding that runs counter to prevailing wisdom, scientists have associated aspirin use with cancer of the pancreas.

Since past studies linked chronic inflammation to various malignancies, the researchers had expected the anti-inflammatory effects of aspirin to suppress pancreatic cancer. Indeed, a smaller study in 2002 found that people taking aspirin had less pancreatic cancer than people not taking aspirin did.

Finding the opposite was "quite a surprise" says Eva S. Schernhammer, an epidemiologist at Harvard Medical School and Brigham and Women's Hospital in Boston, who coauthored the new study. It appears in the Jan. 7 Journal of the National Cancer Institute.

Pancreatic cancer is uncommon but rapidly fatal, mainly because the early stages of the malignancy often go undetected and the pancreas is difficult to examine and treat.

Schernhammer and her colleagues analyzed health information on 88,378 female nurses that was amassed between 1980 and 1998. All the nurses were free of cancer at the start of that period, but 161 subsequently developed pancreatic cancer. Every 2 years during the study, the nurses completed questionnaires on their aspirin use and other health factors.

The data revealed that women who reported in two of three consecutive questionnaires that they were taking more than 14 aspirin tablets a week were nearly twice as likely to get pancreatic cancer as were their counterparts who didn't use aspirin. Women who said they took four to six tablets a week were 29 percent more likely to develop cancer than were women taking no aspirin. Smaller doses produced smaller effects.

Most aspirin users took standard 325-milligram tablets. Low-dose tablets, once called baby aspirin, contain only 81 mg of aspirin, so people who take those pills for heart health should continue to do so, Schernhammer says. The team didn't have sufficient data to assess the impact of other anti-inflammatory drugs.

The connection between inflammation and cancer remains unclear, says epidemiologist John A. Baron of Dartmouth Medical School in Hanover, N.H. For example, inflammatory infections of the liver and the stomach are directly linked to cancer of those organs, yet arthritic joints--centers of inflammation--are rarely cancerous, he says.

A possible explanation for the new finding stems from aspirin's capacity to alter lipoxygenase-enzyme production in the body. In laboratory tests, some of these enzymes abet cancer and others suppress it. Boosting a procancer enzyme or inhibiting an anticancer one could facilitate tumor growth, Schernhammer and her colleagues speculate.

The new findings should prompt scientists to search other large databases for the effects of anti-inflammatory drugs on cancer risk, says Kristen E. Anderson, an epidemiologist at the University of Minnesota in Minneapolis-St. Paul and a coauthor of the 2002 study indicating that aspirin protects people from pancreatic cancer.