Long-Term Use of Aspirin and Nonsteroidal Anti-inflammatory Drugs May Be Associated With Reduced Colorectal Cancer Risk
A large population-based control study of the use of low-dose aspirin or other nonsteroidal anti-inflammatory drugs and colorectal cancer risk has found that taking 75 mg to 150 mg of aspirin for 5 years or longer was associated with a 27% reduced risk of colorectal cancer. In addition, 5 or more years of continuous use of nonsteroidal anti-inflammatory drugs was associated with a 30% to 45% reduction in colorectal cancer risk. Nonaspirin nonsteroidal anti-inflammatory drugs with the highest cyclooxygenase-2 (COX-2) selectivity had the largest risk reductions.
The potential harms of taking these medications long-term—gastrointestinal bleeding and, for most nonaspirin nonsteroidal anti-inflammatory drugs, cardiovascular risks—need to be balanced against the chemopreventive benefits found in this study, according to the researchers. The study by Friis et al was published in the Annals of Internal Medicine.
Study Methodology
The researchers identified 10,280 case patients with colorectal cancer and 102,800 control participants from registry data from the Danish Cancer Registry, Aarhus University Prescription Database, Danish National Patient Registry, and Danish Civil Registration System. Eligible case patients had a verified first diagnosis of colorectal cancer between 1994 and 2011, ensuring at least 5 years of prescription coverage before a possible colorectal cancer diagnosis.
Patients were between the ages of 30 and 85 years at cancer diagnosis. Using risk-set sampling and applying the same selection criteria as they did for the patients, the researchers matched 10 population control participants for each patient according to birth year, sex, and region of northern Denmark.
Data on drug use, comorbid conditions, and history of colonoscopy were obtained from prescription and patient registries. Use of low-dose aspirin (75 mg to 150 mg) and nonaspirin nonsteroidal anti-inflammatory drugs was defined according to type, estimated dose, duration, and consistency of use.
Study Findings
Among 10,280 case patients and 102,800 control participants, the adjusted odds ratios (ORs) for colorectal cancer associated with ever use (at least two prescriptions) of low-dose aspirin and nonaspirin nonsteroidal anti-inflammatory drugs were 1.03 (95% confidence interval [CI] = 0.98–1.09) and 0.94 (95% CI = 0.90–0.98), respectively. Continuous long-term use (≥ 5 years) of low-dose aspirin was associated with a 27% reduction in colorectal cancer risk (OR = 0.73, 95% CI = 0.54–0.99), whereas the overall odds ratio for cumulative long-term use (continuous or noncontinuous) was close to unity.
Nonaspirin nonsteroidal anti-inflammatory drug use was associated with a substantial reduction in colorectal cancer risk, 30% to 45%, particularly for long-term, high-intensity use (average defined daily dose ≥ 0.3) of agents with high COX-2 selectivity (OR = 0.57; 95% CI = 0.44–0.74).
The study authors cautioned that because data were not available on over-the-counter purchases of high-dose aspirin and low-dose ibuprofen or nonsteroidal anti-inflammatory drug dosing schedules, they were unable to adjust for confounding by some risk factors.
Balancing the Risks and Benefits
“Our results indicate that if aspirin is taken at doses of 75 mg to 150 mg, long-term, continuous use is necessary to achieve a substantial protective effect against colorectal cancer. The potential use of aspirin and nonaspirin [nonsteroidal anti-inflammatory drugs] for the prevention of colorectal cancer is limited by the risk of gastrointestinal bleeding, and, for most nonaspirin [nonsteroidal anti-inflammatory drugs], cardiovascular risks. These potential harms will need to be balanced against the chemopreventive benefits that our results indicate,” concluded the study authors.
Søren Friis, MD, of the Danish Cancer Society in Copenhagen, is the corresponding author of this study.
Funding for this study was provided by the Danish Cancer Society and Aarhus University Research Foundation. For full disclosures of the study authors, visit www.annals.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
