Long-term, continuous use of low-dose aspirin and nonaspirin nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with decreased colorectal cancer risk. The findings of a population-based, case-control study were published in Annals of Internal Medicine (2015; doi:10.7326/M15-0039).

Colorectal cancer is the third most common non-skin cancer in the world. Colorectal neoplasms have a long progression, making colorectal cancer an obvious target for preventive interventions. Studies have suggested that regular aspirin and other NSAID use can reduce colorectal cancer risk, but a recent comprehensive review concluded that more research is needed to determine the optimal use of aspirin for cancer prevention.

Researchers reviewed data on drug use, comorbid conditions, and history of colonoscopy from prescription and patient registries in Northern Denmark. The study included data from 10,280 patients and 102,800 control participants. The data available described type (low-dose aspirin or nonaspirin NSAIDs), estimated dose, duration, and consistency of use. Low-dose aspirin was defined as 75-150 mg.

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Based on prescriptions filled, taking 75 to 150 mg of aspirin continuously for 5 years or longer was associated with a 27% reduced risk for colorectal cancer. Five or more years of continuous nonaspirin NSAID use was associated with a 30% to 45% reduction in colorectal cancer risk. However, cumulative use that was either continuous or noncontinuous did not affect risk.

Nonaspirin NSAIDs with the highest COX-2 selectivity were associated with the largest risk reductions.

The authors caution that patients with the highest adherence comprised only about 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 that of the general population. In addition, other lifestyle factors were not measured.