Aspirin in the Chemoprevention of Colorectal Neoplasia: An Overview

Considerable evidence supports the effectiveness of aspirin for chemoprevention of colorectal cancer (CRC) in addition to its well-established benefits in the prevention of vascular disease. Epidemiologic studies have consistently observed an inverse association between aspirin use and risk of CRC. A recent pooled analysis of a long-term post-trial follow-up of nearly 14,000 patients from 4 randomized, cardiovascular disease prevention trials showed that daily aspirin treatment for about 5 years was associated with a 34% reduction in 20-year CRC mortality. A separate meta-analysis of nearly 3,000 patients with a history of colorectal adenoma or cancer in 4 randomized adenoma prevention trials demonstrated that aspirin reduced the occurrence of advanced adenomas by 28% and any adenoma by 17%. Aspirin has also been shown to be beneficial in a clinical trial of patients with Lynch syndrome, a hereditary CRC syndrome; in those treated with aspirin for at least 2 years, there was a ≥ 50% reduction in the risk of CRC commencing 5 years after randomization and after aspirin had been discontinued. A few observational studies have shown an increase in survival among patients with CRC who use aspirin. Taken together, these findings strengthen the case for consideration of long-term aspirin use in CRC prevention. Despite these compelling data, there is a lack of consensus about the balance of risks and benefits associated with long-term aspirin use, particularly in low-risk populations. The optimal dose to use for cancer prevention and the precise mechanism underlying aspirin’s anticancer effect require further investigation