Colorectal cancer is the third most common nonskin cancer worldwide, and because colorectal neoplasms take time to develop, the disease often is targeted for preventive interventions.
Previous studies have suggested that regular use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce the risk of colorectal cancer, although a recent comprehensive review(annonc.oxfordjournals.org) concluded that more research is needed to determine the optimal dose and duration of use for cancer prevention.
Researchers in Denmark recently tried their hand at studying the issue, conducting a population-based, case-control study(annals.org) that found associations between long-term, continuous use of low-dose aspirin and long-term use of nonaspirin NSAIDs and decreased colorectal cancer risk. The study was published online Aug. 25 in Annals of Internal Medicine.
Family Physician Expert's Take
Robert Rich, M.D., chair of the AAFP Commission on Health of the Public and Science, told AAFP News that although the study suggests a positive effect from long-term use of aspirin/NSAIDs to prevent colorectal cancer, it doesn't establish a clear relationship between using these drugs and cancer prevention. To do that, he noted, confounding factors that could have accounted for the observed effect would need to be ruled out.
- Previous studies have suggested that regular use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce colorectal cancer risk, although a recent comprehensive review concluded that more research is needed to determine the optimal dose and duration of use for this purpose.
- Now, researchers in Denmark have conducted a population-based, case-control study that found associations between long-term, continuous use of low-dose aspirin and long-term NSAID use and decreased colorectal cancer risk.
- One family physician expert noted that both the AAFP and the U.S. Preventive Services Task Force recommend against the routine use of aspirin or NSAIDs to prevent colorectal cancer in individuals at average risk for the disease.
Rich also noted that in 2007, the U.S. Preventive Services Task Force (USPSTF) recommended(www.uspreventiveservicestaskforce.org) against routine use of aspirin or NSAIDs to prevent colorectal cancer in individuals at average risk for the disease and said this study does little to change the weight of that recommendation. The AAFP issued the same recommendation in 2008.
But Rich said he was curious if the large number of adult patients who take NSAIDs long-term for managing arthritis and musculoskeletal pain would see this potential added benefit of colorectal cancer prevention even though many patients don't take NSAIDS continuously due to the many side effects of their chronic use.
Researchers reviewed data on drug use, comorbid conditions and history of colonoscopy from prescription and patient registries in Northern Denmark. Based on prescriptions filled, patients taking 75 mg to 150 mg of aspirin continuously for five years or longer had a 27 percent lower risk for colorectal cancer compared with a control group. Five or more years of continuous nonaspirin NSAID use was associated with a 30 percent to 45 percent reduction in colorectal cancer risk. Nonaspirin NSAIDs with the highest cyclooxygenase-2 enzyme selectivity were associated with the largest risk reductions.
The authors cautioned that patients with the highest adherence comprised only about 2 percent to 3 percent of all low-dose aspirin users in the study population, and this group's risk for colorectal cancer might differ from that of the general population.
Rich added that the study was limited by a lack of data about patient purchase and use of OTC aspirin and NSAIDs, as well as a lack of data on NSAID dosing regimens.
"As a result of that data deficiency, a patient reportedly on low-dose aspirin/NSAID therapy may have actually been taking high-dose therapy when OTC usage is added to any prescribed therapy," Rich explained. "Additionally, the study did not take into account confounding patient risk factors which could have skewed a patient's risk of developing colorectal cancer, both positively and negatively."
All in all, he added, the most important benefit of this study may be to add to the evidence included in the USPSTF's updated review(www.uspreventiveservicestaskforce.org) of research on the topic, which is currently in progress.
More Fodder for Patient Discussions
Rich said family physicians should expect the study to spur additional questions from their patients who are on daily aspirin/NSAID therapy and its possible preventive effects on colorectal cancer.
Members may also expect to receive an occasional question from their patients not already on daily aspirin/NSAID therapy as to whether they would benefit from the treatment to prevent colorectal cancer, particularly if they have a family history of that cancer, he said.
"As always, any discussion of a therapy, such as daily aspirin therapy, must include a discussion of harms versus benefits, and for an individual patient, the harms of such therapy may be considerable," Rich said.
Related AAFP News Coverage
FDA Orders Across-the-board Risk Updates to NSAIDs Labels
Agency Calls for Stronger Warnings About Cardiovascular Effects