The oft-quoted benefits of low-dose aspirin in preventing cancer have been called into question this week after long-term data from the Women’s Health Study showed no positive effect.

The study involved almost 40,000 healthy women over the age of 45 who received either 10mg aspirin or placebo every other day and were followed up over a 10-year period. Results showed no effect of aspirin on total cancer rates – including breast and colorectal tumours – or on mortality figures. However, there was a trend towards a reduction in both risk and mortality for lung cancer. “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,” say the study investigators, led by Nancy Cook from Harvard Medical School in Boston, Massachusetts, USA.

Aspirin has been long believed to have a positive impact on cancer rates because of its anti-inflammatory mechanism and a potential role as an antioxidant. However, the disappointing news comes alongside research earlier this week that showed taking low-dose aspirin could also increase resistance to the drug for patients with already-established heart disease [[05/07/05e]].