Among individuals with prior colorectal neoplasia, low-dose aspirin might be the safest choice for preventing colorectal cancer, though non-aspirin NSAIDs may be more effective, according to a systematic review and meta-analysis.
"Our findings extend the recent U.S. Preventive Services Task Force (USPSTF) recommendations supporting use of low-dose aspirin for primary prevention of colorectal neoplasia to its use as a secondary chemopreventive agent in patients with prior colorectal neoplasia," Dr. Siddharth Singh from the University of California, San Diego, in La Jolla told Reuters Health by email.
A number of medications and nutritional supplements have been studied for their ability to prevent colorectal cancer in people with previous colorectal neoplasia, with variable efficacy in randomized controlled trials. Given the lack of head-to-head trials, their relative safety and efficacy are not known.
Dr. Singh and colleagues performed a pairwise meta-analysis and Bayesian network meta-analysis to compare the relative efficacy and safety of low- and high-dose aspirin, non-aspirin NSAIDs, calcium, vitamin D, and folic acid, alone or in combination, for the prevention of colorectal cancer within three to five years of the index colonoscopy in people with previous colorectal neoplasia.
Compared with placebo, non-aspirin NSAIDs were best for preventing advanced metachronous neoplasia (a 63% odds reduction), followed by low-dose aspirin (a 29% reduction), aspirin plus folic acid (a 27% reduction), aspirin plus calcium plus vitamin D (a 29% reduction), and high-dose aspirin (a 19% reduction), the researchers report in The BMJ, online December 5.
Non-aspirin NSAIDs were also superior for preventing any metachronous neoplasia, while low- and high-dose aspirin had comparable efficacy. However, non-aspirin NSAIDs had 23% greater odds than placebo of causing adverse effects, whereas low-dose aspirin was ranked the safest among chemoprevention agents.
"In patients at high-risk of metachronous colorectal neoplasia with low cardiovascular risk, particularly those for whom colonoscopic surveillance would be challenging, non-selective NSAIDs may be considered for prevention of advanced neoplasia," Dr. Singh concluded. "On the other hand, low-dose aspirin may be useful for all patients, regardless of baseline neoplasia risk, given its favorable risk-benefit profile."
"Shared decision making with a thorough understanding of patients' values and preferences in the context of risks and benefits of each agent would be helpful," the researchers write in their report. "Additionally, given the low confidence in several estimates, molecular phenotyping and precision chemoprevention trials are needed to determine how people can be optimally risk stratified according to safety of treatment and likelihood of response."