Prolonged Regular Aspirin Use May Increase Pancreatic Cancer Risk

Laurie Barclay, MD

January 06, 2004

Jan. 6, 2004 — An analysis of data from the Nurses' Health Study, published in the Jan. 7 issue of the Journal of the National Cancer Institute, suggests that regular use of aspirin for 20 years or more is associated with an increased risk of pancreatic cancer. Because this differs from findings in other studies, the editorialist suggests that there are no easy answers, but that the conflict should be an impetus to additional research.

Earlier studies have shown that use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce risk of some cancers and precancerous lesions, and in vitro and animal models have suggested that aspirin and NSAIDs may inhibit the development of pancreatic cancer. However, studies analyzing the association between analgesic use and pancreatic cancer in humans have been infrequent and have yielded inconsistent results.

"Our findings do not support a protective effect of analgesic use on the risk of pancreatic cancer," write Eva S. Schernhammer, MD, DrPH, from the Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, and colleagues. "Rather, aspirin appears to increase the risk of pancreatic cancer after extended periods of use."

As part of the Nurses' Health Study, beginning in 1980, 88,378 women completed biennial questionnaires, including items about aspirin use. Of these women, 34% were current regular aspirin users, defined as consumption of two or more 325 mg aspirin tablets weekly, and 66% consumed fewer than two tablets weekly.

During 18 years of follow-up, 161 new cases of pancreatic cancer occurred, with no statistically significant difference in risk of pancreatic cancer between regular aspirin users and nonusers. However, compared with women who regularly consumed fewer than two aspirin tablets per week, women with more than 20 years of regular aspirin use had a 58% increased risk of pancreatic cancer (relative risk [RR], 1.58; 95% confidence interval [CI], 1.03 - 2.43; P = .01 for trend).

Compared with women who were nonusers during the same time period, the risk of pancreatic cancer in regular aspirin users increased with increasing aspirin dose ( P = .02 for trend). Compared with nonusers, women who consumed 14 or more aspirin tablets weekly had an 86% increased risk of pancreatic cancer (RR = 1.86; 95% CI, 1.03 - 3.35; P = .02 for trend).

Higher pancreatic cancer risk linked to aspirin use seemed to be confined to women with a higher body mass index, suggesting that obesity may have served as a marker for inflammation.

"Risks and benefits associated with the use of aspirin have to be weighed carefully in any recommendations made by health care providers," the authors write.

In an accompanying editorial, John A. Baron, MD, from Dartmouth Medical School in Hanover, New Hampshire, notes that these findings raise questions about the actions of aspirin and other NSAIDs and the mechanisms underlying pancreatic cancer.

"There are no easy answers to the question of what aspirin and other NSAIDs do to pancreatic carcinogenesis," he writes. "Fortunately, conflicting data from diverse threads of research are often a very effective push toward scientific progress."

J Natl Cancer Inst. 2004;96:4-5, 22-28

Reviewed by Gary D. Vogin, MD

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