Does Low-Dose Aspirin Lower Cancer Risk in Women?

Recent data from multiple trials suggest that long-term daily use of aspirin lowers risk for colorectal cancer (NEJM JW Gen Med Apr 24 2012). The randomized Women's Health Study (WHS) showed cancer incidence (total or colorectal) was the same after 10 years of alternate-day, low-dose aspirin (100 mg) as after placebo (NEJM JW Gen Med Aug 2 2005). At the end of that trial in 2004, participants were asked to continue in an observational study; 34,000 agreed, and the researchers now report longer-term outcomes.

During a median follow-up of 18 years, incidence of total cancer, breast cancer, and lung cancer did not differ between the women initially randomized to aspirin and those randomized to placebo, whereas colorectal cancer incidence was si…