Large-scale trial indicates no benefit from low-dose aspirin in preventing cancer in healthy women


A major study that includes nearly 40,000 healthy women found no benefit on preventing cancer from taking low-dose aspirin, or benefit on preventing cancer or cardiovascular disease from taking vitamin E, according to two articles in the July 6 issue of JAMA.

A growing body of literature has supported a protective effect of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) on the development of cancer, according to background information in the first article. Observational epidemiological investigations suggest a strong inverse association, with risk reductions as high as 20 percent to 50 percent for various cancer sites. In contrast with the observational evidence on cancer incidence, data from randomized trials, which provide more definitive results due to their ability to minimize bias and confounding, have been far more limited. The Physicians' Health Study (PHS) found no effect on colorectal cancer of 325 mg aspirin administered every other day over a 5-year randomized period or in post trial follow-up. In addition, no randomized trial has yet assessed the impact of aspirin on the development of breast cancer.

The Women's Health Study (WHS) was a randomized, double-blind, placebo-controlled trial, conducted between September 1992 and March 2004, evaluating the balance of benefits and risks of 100 mg of aspirin every other day, and 600 IU of vitamin E every other day on the primary prevention of cardiovascular disease and cancer in a cohort of 39,876 healthy female health care professionals over an average duration of 10.1 years.

In the first article, Nancy R. Cook, Sc.D., of Brigham and Women's Hospital and Harvard Medical School, Boston, and colleagues evaluated the findings for the aspirin component of the WHS with regard to cancer risk. In this part of the study, 19,934 women received a dose of 100 mg of aspirin every other day and 19,942 women received placebo.

The researchers found that aspirin had no observed effect on total cancer, breast cancer, colorectal cancer, or cancer of any other site, with the exception of lung cancer for which there was a trend toward reduction in risk (22 percent reduced risk). There was also no reduction in cancer death either overall or by site, except for lung cancer death (30 percent reduced risk). No evidence of differential effects of aspirin by follow-up time or interaction with vitamin E was found.

"The findings from the WHS suggest that aspirin at a dose of 100 mg every other day is not effective in reducing risk of cancer in healthy women, although a beneficial effect on lung cancer cannot be ruled out. This large study of almost 40,000 women had a duration of 10 years of treatment and follow-up, which was the longest of any trial completed to date, and should be sufficient to detect long-term effects. To determine whether higher doses of aspirin taken daily would be effective in cancer prevention requires direct randomized trial data. Such data would need to be considered in the context of risk of gastrointestinal adverse effects before recommending higher-dose aspirin for cancer chemoprevention among low-risk individuals," the authors conclude.

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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