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Comparative effectiveness of chemopreventive interventions for colorectal cancer: protocol for a systematic review and network meta-analysis of randomised controlled trials.

BACKGROUND
Colorectal cancer (CRC) is the third most common cancer worldwide and is associated with substantial socioeconomic burden. Despite considerable research, including numerous randomised controlled trials (RCTs) and systematic reviews assessed the effect of various chemopreventive interventions for CRC, there remains uncertainty regarding the comparative effectiveness of these agents. No network meta-analytic study has been published to evaluate the efficacies of these agents for CRC. Therefore, the aim of this study is to summarise the direct and indirect evidence for these interventions to prevent CRC in average-high risk individuals, and to rank these agents for practical consideration.


METHODS
We will acquire eligible studies through a systematic search of MEDLINE, EMBASE, the Cochrane Central Registry of Controlled Trials, CINAHL plus, IPA and clinicaltrials.gov website. The Cochrane Risk of Bias Tool will be used to assess the quality of included studies. The primary outcomes are the incidence of CRC, the incidence/recurrence of any adenoma or change in polyp burden (number or size). Quantitative synthesis or meta-analysis will be considered. We will also construct a network meta-analysis (NMA) to improve precision of the comparisons among chemo-preventive interventions by combining direct and indirect evidence. The probability of each treatment being the best and/or safest, the number-needed-to-treat [NNT; 95% credible interval (CrIs)], and the number-needed-to-harm (NNH; 95% CrIs) will be calculated to provide measures of treatment efficacy. The GRADE approach will be used to rate the quality of evidence of estimates derived from NMA.


RESULTS
This protocol has been registered (registration number: CRD42015025849) with the PROSPERO (International Prospective Register of Systematic Reviews). The procedures of this systematic review and NMA will be conducted in accordance with the PRISMA-compliant guideline. The results of this systematic review and NMA will be submitted to a peer-reviewed journal for publication.


CONCLUSIONS
To the best of our knowledge, this study will be the first NMA to identify the comparative effectiveness of interventions for the prevention of CRC. The results of our study will update evidence for chemoprevention of CRC, identify key areas for future research, and provide a framework for conducting large systematic reviews involving indirect comparisons.