The continuous, long-term use of low-dose aspirin and NSAIDs appeared to reduce the risk for colorectal cancer, according to results of a population-based, case-control study conducted in Denmark.
Previous studies have shown aspirin and NSAIDs may reduce colorectal cancer risk; however, data are lacking about the duration and intensity of aspirin and NSAID use in relation to risk reduction.
Søren Friis, MD, of the Danish Cancer Society Research Centre in Copenhagen, and colleagues, thus, sought to assess the optimal use of aspirin for cancer prevention.
The analysis included 10,280 case patients from Northern Denmark who had a histologically verified initial diagnosis of colorectal cancer between 1994 and 2011. Researchers matched 10 controls per patient (n = 102,800 controls) according to birth year, sex and area of residence.
Similar proportions of each cohort reported ever use — defined as at least two prescriptions — of low-dose aspirin (case patients, 22.3%; controls, 22.4%) or NSAIDs (case patients, 45.1%; controls, 46.7%).
Ever use of low-dose aspirin did not significantly reduce the risk for colorectal cancer (OR =1.03; 95% CI, 0.98-1.09), whereas ever use of NSAIDs marginally reduced colorectal cancer risk (OR = 0.94; 95% CI, 0.9-0.98).
However, continuous low-dose aspirin — or 75 mg to 150 mg — use for at least 5 years conferred a 27% risk reduction for colorectal cancer (OR = 0.73; 95% CI, 0.54-0.99).
“Caution should be exercised when interpreting the results about long-term continuous use of low-dose aspirin in patients with the highest adherence,” Friis and colleagues wrote. “This high-adherence set comprised only 2% to 3% of all low-dose aspirin users in the study population and these persons may have a risk profile for colorectal cancer that differs from the general population.”
Further, at least 5 years of nonaspirin NSAID use — with an estimated average 0.3 defined daily dose — resulted in a 30% reduction in colorectal cancer risk (OR = 0.7; 95% CI, 0.62-0.78). Consistent 5-year NSAID use with at least two prescriptions per year also reduced colorectal cancer risk (OR = 0.64; 95% CI, 0.52-0.8).
Analyses stratified according to type of nonaspirin NSAID showed long-term, high-intensity use of COX-2 selective NSAIDs conferred a 43% reduction in colorectal cancer risk (OR = 0.57; 95% CI, 0.44-0.74).
Researchers noted these data may be limited due to the lack of data on the purchase of over-the-counter high-dose aspirin, ibuprofen or NSAID dosing schedules.
“Our results indicate that if aspirin is taken at doses of 75-150 mg long term, continuous use is necessary to achieve a substantial protective effect against colorectal cancer,” the researchers concluded. “The potential use of aspirin and nonaspirin NSAIDs for the prevention of colorectal cancer is limited by the risk for gastrointestinal bleeding and, for most NSAIDs, cardiovascular risks. These potential harms will need to be balanced against the chemopreventive benefits that our results indicate.” – by Anthony SanFilippo
Disclosure: The researchers report no relevant financial disclosures.