Researchers determine the effects of aspirin in preventing the development of recurrent colorectal tumors to solidify recommendations for their use.
The presence of adenomas (benign tumors) in the colon prompts immediate attention since the majority of cancers develop from an adenoma. Patients who are most at risk of developing new adenomas are those with a history of colorectal cancer or adenomas. Several small studies have suggested that aspirin and NSAIDs may be beneficial in preventing future adenomas. Unfortunately, due to the small number of patients in previous trials and the small number of trials performed, no conclusive evidence has yet been published.
Researchers at the International Medical University of Malaysia conducted a systematic review of randomized controlled trials and post-trial reports that followed adult patients with a history of colorectal cancer or adenomas for at least one year. The primary aim of this study was to compare the effects of aspirin or NSAIDs of any dose in preventing colorectal adenomas in patients with a history of colorectal cancer or adenomas. The results of this review were recently published in BMC Cancer.
Low-Dose Aspirin May Reduce Risk of Recurrent Tumors
Studying the effects of aspirin, the cumulative data suggest that aspirin in any dose, taken for two to four years, can reduce the risk of developing any recurrent adenomas. Since aspirin may cause cardiovascular and gastrointestinal side effects at higher doses, the researchers stratified the data based on dose. Low-dose aspirin still showed a statistically significant decrease in the risk of developing any recurrent adenomas. At higher doses of aspirin, researchers noted a non-significant reduction in risk of adenomas and a statistically significant reduction in recurrent advanced carcinomas.
For other NSAIDs, the systematic review showed statistically significant reductions in the risk of developing recurrent adenomas and advanced adenomas over a three year follow-up period. Nevertheless, the important adverse events profile of the class of NSAIDs called COX-2 inhibitors limits its use as a possible protective agent against colorectal cancer.
No Conclusions About Protective Effects After Use
Another important factor when considering the beneficial effects of aspirin and NSAIDs on recurrent adenomas is the treatment duration. The researchers analyzed four post-trial reports to determine whether the protective effects of aspirin and NSAIDs ceases once the drug is withdrawn. Unfortunately, due to several limitations on the study size, the number of trials, and the limited follow-up duration, no conclusions can be drawn on the loss of effect once the drug is withdrawn.
Aspirin and NSAIDs seem to have beneficial effects on preventing recurrent adenomas in patients with a history of colorectal cancer or adenomas. Aspirin has a better side effect profile than the NSAIDs used in the trials. Further studies are required to confirm the risk of recurrence once drug therapy is ceased. Additionally, since low-dose aspirin seems to be safe and effective for preventing colorectal adenomas in patients with a history of colorectal cancer and adenomas, high quality randomized controlled trials are also required to confirm the presence of the benefits in reducing adenoma recurrence risk.
Written by Jessica Caporuscio, PharmD
Reference: Veettil SK, Lim KG, Ching SM, et al. Effects of aspirin and non-aspirin nonsteroidal anti-inflammatory drugs on the incidence of recurrent colorectal adenomas: a systematic review with meta-analysis and trial sequential analysis of randomized clinical trials. BMC Cancer. 2017