J Breast Cancer.  2015 Sep;18(3):264-270. 10.4048/jbc.2015.18.3.264.

Association between Metformin Therapy and Breast Cancer Incidence and Mortality: Evidence from a Meta-Analysis

Affiliations
  • 1Department of Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China. liushengchun1968@126.com
  • 2Department of Cardiovascular Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.

Abstract

PURPOSE
Metformin may be associated with a decreased risk of breast cancer. We performed a meta-analysis to assess the effect of metformin intake on breast cancer risk and mortality.
METHODS
We performed a PubMed and EMbase search for all available studies that described the risk of breast cancer and all-cause mortality in relation to the use of metformin among patients with type 2 diabetes mellitus. Pooled relative risks (RRs) were determined using a random effects model to assess the strength of association between metformin and the risk of breast cancer.
RESULTS
Fifteen articles from PubMed satisfied the inclusion criteria, including a total of 838,333 participants. Compared with the control group, metformin use was not related to a reduced incidence of breast cancer (RR, 0.964; 95% confidence interval [CI], 0.761-1.221; p=0.761). However, metformin therapy was associated with decreased all-cause mortality (RR, 0.652; 95% CI, 0.488-0.873; p=0.004). No obvious publication bias was detected (incidence: p(Begg)=0.755, p(Egger)=0.008; mortality: p(Begg)=0.072, p(Egger)=0.185).
CONCLUSION
The present study suggested that metformin therapy may decrease the all-cause mortality of patients affected by breast cancer. However, this finding should be considered carefully and confirmed with further studies.

Keyword

Breast neoplasms; Meta-analysis; Metformin; Risk assessment

MeSH Terms

Breast Neoplasms*
Breast*
Diabetes Mellitus, Type 2
Humans
Incidence*
Metformin*
Mortality*
Publication Bias
Risk Assessment
Metformin

Figure

  • Figure 1 Flow chart of literatures selection for meta-analysis. Flow chart shows literature search for studies in relation to association between metformin and breast cancer. *EMbase was also searched but with no additional articles.

  • Figure 2 Overall pooled relative risk (RR) of studies on incidence of breast cancer. Forest plot shows the association between metformin therapy among women with diabetes and incidence of breast cancer. Weights are from random effects analysis. CI=confidence interval.

  • Figure 3 Forest plot of overall studies on mortality of breast cancer. Forest plot shows the association between metformin therapy and mortality of breast cancer. Weights are from random effects analysis. RR=relative risk; CI=confidence interval.


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