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Review
. 2016 Feb;95(7):e2749.
doi: 10.1097/MD.0000000000002749.

Metformin Is Associated With Slightly Reduced Risk of Colorectal Cancer and Moderate Survival Benefits in Diabetes Mellitus: A Meta-Analysis

Xing-Kang He  1 , Ting-Ting Su, Jian-Min Si, Lei-Min Sun
Affiliations
Review

Metformin Is Associated With Slightly Reduced Risk of Colorectal Cancer and Moderate Survival Benefits in Diabetes Mellitus: A Meta-Analysis

Xing-Kang He et al. Medicine (Baltimore). 2016 Feb.

Abstract

To systematically assess the effect of metformin on colorectal cancer (CRC) risk and mortality in type 2 diabetes mellitus (T2DM) patients. We conducted a systematic search of PubMed, Web of Science, and the Cochrane Library databases for relevant articles before August 2015. Two investigators identified and extracted data independently. We adopted adjusted estimates to calculate summary estimates with 95% confidence interval (CI) using either a fixed-effects or a random-effects model. Subgroup and sensitivity analyses were conducted to evaluate the robustness of the pooled results. The risk of publication bias was assessed by examining funnel plot asymmetry as well as Begg test and Egger test. Fifteen studies on CRC incidence and 6 studies on CRC survival were finally included in our meta-analysis. The pooled odds ratio (OR) of observational studies illustrated that a slight 10% reduction of CRC incidence was associated with metformin use (OR = 0.90, 95% CI: 0.85-0.96). Furthermore, the pooled hazard ratio (HR) revealed an improved survival outcome for metformin users in CRC patients compared to nonusers (HR = 0.68, 95% CI: 0.58-081). There was no publication bias across studies. Our meta-analysis demonstrated that metformin therapy could slightly reduce CRC incidence and moderately improve the survival outcomes in patients with T2DM. More prospective studies are warranted to certify this protective association.

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Conflict of interest statement

The authors have no conflicts of interest to disclose.

Figures

FIGURE 1
FIGURE 1
Flow diagram summarizing study identification and selection.
FIGURE 2
FIGURE 2
Meta-analysis of the association between metformin use and colorectal cancer risk in patients with diabetes mellitus.
FIGURE 3
FIGURE 3
Funnel plot analysis to detect publication bias.
FIGURE 4
FIGURE 4
Meta-analysis of the association between metformin use and all-cause mortality in patients with diabetes mellitus.
See this image and copyright information in PMC

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