A new report from the Nurse's Health Study finds that regular, long-term aspirin use can significantly reduce the risk of colorectal cancer, as suggested by several earlier studies.
However, the benefit appears to require more than a decade and is strongest at dose levels associated with a greater risk of side effects such as bleeding. Similar results were found for non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen and naproxen.
The report - from researchers at Massachusetts General Hospital (MGH), Brigham and Women's Hospital and Dana-Farber Cancer Institute - appears in the August 24 Journal of the American Medical Association.
"Several earlier studies have found that, among patients with a history of colon polyps or cancer, regular aspirin treatment prevents the recurrence of precancerous polyps. However, the ability of aspirin to reduce the long-term incidence of invasive cancer has not been well-demonstrated," says Andrew Chan, MD, MPH, of the MGH Gastrointestinal Unit, the paper's lead author. "Our study did find a protective effect of long-term aspirin use on risk of invasive colorectal cancer, but only at dosage levels considerably higher than those used to prevent cardiovascular disease."
The Nurses' Health Study (NHS) has followed more than 120,000 female registered nurses since the mid-1970s, asking them to complete a questionnaire on risk factors for and incidence of cancer and cardiovascular disease every two years. In 1980, assessments of diet and the use of aspirin and NSAIDS were added. The current report analyzes information from almost 83,000 NHS participants, among which 962 cases of colorectal cancer were diagnosed during the 20-year study period.