Systematic review with meta-analysis: the comparative effectiveness of aspirin vs. screening for colorectal cancer prevention.

BACKGROUND: Both aspirin use and screening with flexible sigmoidoscopy or guaiac faecal occult blood testing (FOBT) may reduce mortality from colorectal cancer, but comparative effectiveness of these interventions is unknown.

AIM: To compare aspirin to guaiac FOBT screening with regard to incidence and mortality of colorectal cancer in a network meta-analysis.

METHODS: We searched Medline, EMBASE and the COCHRANE central register (CENTRAL) for relevant randomised trials identified until 31 October 2015. Randomised trials in average-risk populations that reported colorectal cancer mortality, colorectal cancer incidence, or both, with a minimum follow-up of 2 years, and more than 100 randomised individuals were included. Three investigators independently extracted data. We calculated relative risks [RR with 95% predictive intervals (PrIs)] for the comparison of the interventions by frequentist network meta-analyses.

RESULTS: The effect of aspirin on colorectal cancer mortality was similar to FOBT (RR 1.03; 95% PrI 0.76-1.39) and flexible sigmoidoscopy (RR 1.16; 95% PrI 0.84-1.60). Aspirin was more effective than FOBT (RR 0.36; 95% PrI 0.22-0.59) and flexible sigmoidoscopy (RR 0.37; 95% PrI 0.22-0.62) in preventing death from or cancer in the proximal colon. Aspirin was equally effective as screening in reducing colorectal cancer incidence, while flexible sigmoidoscopy was superior to FOBT (RR 0.84; 95% PrI 0.72-0.97).

CONCLUSIONS: Low-dose aspirin seems to be equally effective as flexible sigmoidoscopy or guaiac FOBT screening to reduce colorectal cancer incidence and mortality, and more effective for cancers in the proximal colon. A randomised comparative effectiveness trial of aspirin vs. screening is warranted.