The Bottom Line: Alternate-day use of low-dose aspirin reduced the risk for colorectal cancer in women after 10 years, according to study results published in the Annals of Internal Medicine. Aspirin did not drop the chances of getting breast or lung cancer.
The Study: Nancy R. Cook, ScD, and colleagues at Harvard Medical School conducted an observational analysis of 39,876 female health professionals enrolled in the Women’s Health Study. The women were randomly assigned 100 mg of aspirin (n=19,934) or placebo (n=19,942) every other day from 1993 to 2004. All participants were aged 45 years or older and had no prior incidence of cardiovascular disease or cancer aside from non-melanoma skin cancer. The women completed yearly questionnaires through 2004 to document medication use and other health information. Invasive cancer incidence served as the primary endpoint. Breast, colorectal and lung cancer incidence served as secondary endpoints. Median follow-up was 10.3 years.
Results: Colorectal cancer incidence was lower in the aspirin group compared with the placebo group (HR=0.80; 95% CI, 0.67-0.97). The most significant reduction was in proximal colon cancer (HR=0.73; 95% CI, 0.55-0.95). The difference in colon cancer incidence between the groups emerged after the 10-year active intervention period, with a post-trial reduction of 42% (HR=0.58; 95% CI, 0.41-0.81).
Aspirin use was associated with increased incidence of gastrointestinal bleeding (HR=1.14; 95% CI, 1.06-1.22) and peptic ulcers (HR=1.17; 95% CI, 1.09-1.27). Three deaths due to gastrointestinal bleeding occurred in each study arm.
My Take: Prior studies suggest daily aspirin use may reduce the risk of getting certain cancers, particularly colorectal cancer, but we have only limited evidence related to the effects of alternate-day aspirin use. And we must remember the researcher’s own warnings about aspirin use: “Aspirin’s adverse effects…cannot be forgotten. Whether new results about long-term benefits for cancer will tip the balance in favor or aspirin remains to be determined.” Here’s the view of a sceptic:
“The lack of a reduction in all-cause mortality, or even in the risk for all cancer, with aspirin in the Women’s Health Study should temper any recommendations for widespread use of aspirin in healthy middle-aged women,” Peter Rothwell, MD, PhD of the University of Oxford wrote in an accompanying editorial.
While not everyone should take a baby aspirin regularly, ask your doctor if you should consider it. You will need to weight your personal risk of disease such as heart attack, stroke, and colon cancer against the risks of aspirin. I’m Dr. Michael Hunter.
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