Long-term, low dose aspirin use linked with lower colorectal cancer risk

In the population-based, case study published Monday in the Annals of Internal Medicine, researchers led by Danish scientists honed in on the patterns of use of aspirin and NSAIDs needed for protection from colorectal cancer.

Long-term, continuous use of low-dose aspirin and non-aspirin nonsteroidal anti-inflammatory drugs is associated with decreased colorectal cancer risk, a study involving a UNC Lineberger Comprehensive Cancer Center researcher found.

In the population-based, case study published Monday in the Annals of Internal Medicine, researchers led by Danish scientists honed in on the patterns of use of aspirin and NSAIDs needed for protection from colorectal cancer. The researchers say the work was needed since, while prior studies showed that aspirin and other NSAIDs can reduce colorectal cancer risk, more work was needed to determine how often those medications needed to be taken, for how long and in what doses.  

“Colorectal cancer is the third most common non-skin cancer in the world, and is an important target for possible preventative strategies,” said John Baron, MD, MS, MSc, a UNC Lineberger member and research professor at the UNC School of Medicine and Gillings School of Global Public Health. “In our study, we sought to gather information needed to help understand how aspirin and other NSAIDs can complement other preventive strategies for the prevention and treatment of cancer and cardiovascular disease. This is a complicated story. Aspirin has cardioprotective properties, as well as a beneficial effect on cancer risk. But aspirin also increases bleeding risk, and other NSAIDs may increase myocardial infarctions and strokes.” 

Researchers reviewed data on drug use, co-morbid conditions, and history of colonoscopy from prescription and patient registries in Northern Denmark. Based on prescriptions filled, the researchers found that taking 75 to 150 mg of aspirin continuously for five years or longer was associated with a 27 percent reduced risk for colorectal cancer, and five or more years of continuous non-aspirin NSAID use was associated with a 30 to 45 percent reduction in colorectal cancer risk. Non-aspirin NDAIDS with the highest COX-2 selectivity were associated with the largest risk reductions. 

Baron stressed that the study reinforced the need for continuous use to prevent colorectal cancer, and that none of these drugs should be taken for prolonged periods of time without consultation with a physician.

The authors cautioned in the paper that patients with the highest adherence comprised only about 2 to 3 percent of all low-dose aspirin users in the study population, and this group may have a risk profile for colorectal cancer that differs from that of the general population. In addition, other lifestyle factors were not measured.

 The study was funded by a Danish Cancer Society grant and by the Aarhus University Research Foundation.

The study’s first author was Søren Friis, MD, of the Danish Cancer Society Research Centre. Additional authors include Anders H. Riis, MSc, of the Department of Clinical Epidemiology at the Aarhus University Hospital; Rune Erichsen, MD, of the Department of Clinical Epidemiology at the Aarhus University Hospital; and senior author Henrik T. Sørensen, MD, DMSc, of the Department of Clinical Epidemiology at Aarhus University Hospital. 

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