Long-term use of alternate-day, low-dose aspirin may reduce risk for colorectal cancer in healthy women.
Evidence has recently emerged that daily aspirin may help to prevent several types of cancer, including colorectal, but there is little evidence for an alternate-day dosing strategy.
Between 1994 and 1996 researchers randomly assigned 38,876 women aged 45 years or older to take either 100 mg of aspirin or placebo every other day. Participants were sent annual supplies of monthly calendar packs containing aspirin or placebo.
At six and 12 months and then yearly through the trial end in March 2004, patients were mailed questionnaires to determine adherence, adverse effects, nonstudy aspirin use, clinical end points, and risk factors. At the end of the intervention period, women were invited for further annual follow up with an opt-out option. Posttrial follow-up for those who did not opt out continued through March 2012.
The researchers writing in Annals of Internal Medicine found that long-term use of alternate-day, low dose aspirin reduced the risk for colorectal cancer but was associated with increased risk for gastrointestinal bleeding. According to the authors, these findings should influence future recommendations on prophylactic aspirin use.