COPENHAGEN, DENMARK. There is considerable evidence that the use of aspirin in daily doses of 300 mg or more for at least 6 months reduces the risk of colorectal cancer (cancer of the colon or rectum). What is much less clear is whether lower doses of aspirin, such as prescribed for heart disease patients, have a similar protective effect.
Danish medical researchers investigated the incidence of cancer in 15,000 men and 14,000 women (39%
between the ages of 50 and 69 years and 55% aged 70 years or older) who had been prescribed a daily
low-dose aspirin (75-150 mg) for heart disease. The participants were followed for up to 9 years with an
average follow-up period of 4.1 years. During this time, a total of 2381 cases of cancer were diagnosed in
the aspirin group. The expected number of cases in a group of 29,000 adults would be 2187. Thus there
was no evidence of an overall protective effect of low-dose aspirin. Specifically, there was no indication that
long-term use of low-dose aspirin was protective against either cancer of the colon or cancer of the rectum.
There was a light, but statistically significant excess of kidney cancer cases among the aspirin users; the
researchers ascribe this to a possible greater incidence of hypertension in this group of heart patients and
point out that hypertension is a risk factor for kidney cancer.