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Review
. 2017 Jan 31;8(5):8843-8853.
doi: 10.18632/oncotarget.13633.

Metformin therapy and the risk of colorectal adenoma in patients with type 2 diabetes: A meta-analysis

Yi-Chao Hou  1 , Qiang Hu  1 , Jiao Huang  1 , Jing-Yuan Fang  1 , Hua Xiong  1
Affiliations
Review

Metformin therapy and the risk of colorectal adenoma in patients with type 2 diabetes: A meta-analysis

Yi-Chao Hou et al. Oncotarget. .

Abstract

Background: Existing data evaluating the impact of metformin on the colorectal adenoma (CRA) risk in patients suffering from type 2 diabetes (T2D) are limited and controversial. We therefore summarized the studies currently available and assessed the relationship between metformin treatment and risk of CRA in T2D patients.

Methods: We systematically searched databases for eligible studies that explored the impact of metformin treatment on the occurrence of CRA in T2D patients from inception to June 2016. The summary odds ratio (OR) estimates with their 95% confidence interval (CI) were derived using random-effect, generic inverse variance methods. Sensitivity analysis and subgroup analysis were performed.

Results: Seven studies involving 7178 participants met the inclusion criteria. The pooling showed that metformin therapy has a 27% decrease in the CRA risk (OR, 0.73; 95% CI, 0.58 - 0.90). In subgroup analysis, we detected that metformin exhibits significant chemoprevention effects in Asia region (OR, 0.68; 95% CI, 0.48 - 0.96). Similar results were identified in both studies with adjusted ORs and high-quality studies (OR, 0.66; 95% CI, 0.50 - 0.86 and OR, 0.70; 95% CI, 0.58 - 0.84, respectively). Of note, an inverse relationship was noted that metformin therapy may result in a significant decrease in the advanced adenoma risk (OR, 0.52; 95% CI, 0.38 - 0.72). Low heterogeneity was observed, however, the results remained robust in multiple sensitivity analyses.

Conclusions: This meta-analysis indicates that metformin therapy is correlated with a significant decrease in the risk of CRA and advanced adenoma in T2D patients. Further confirmatory studies are warranted.

Keywords: advanced adenoma; colorectal adenoma; diabetes; meta-analysis; metformin.

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Conflict of interest statement

CONFLICTS OF INTEREST

The authors declare no potential conflicts of interest.

Figures

Figure 1
Figure 1. Flow diagram of included and excluded trials
Figure 2
Figure 2. Forest plot for the meta-analysis of studies examining the association between metformin treatment and risk of CRA in T2D patients
CI, confidence interval; IV, inverse variance; SE, standard error; CRA, colorectal adenoma; T2D, type 2 diabetes.
Figure 3
Figure 3. Forest plot for the meta-analysis of studies examining the association between metformin treatment and risk of advanced adenoma in T2D patients
CI, confidence interval; IV, inverse variance; SE, standard error; T2D, type 2 diabetes.
See this image and copyright information in PMC

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