Association between Diabetes Mellitus and Breast Cancer Risk: a Meta-analysis of the Literature

Aim/hypothesis: Diabetes and breast cancer are both serious life-threatening diseases across the world. Some studies shows that diabetes is associated with many kinds of tumor, but links with breast cancer remain controversial. The aim of this study was to assess the association the available evidence. Subjects and methods: A meta-analysis was conducted including 16 studies published between 2000 and 2010 and summary relative risks(RRs) with 95% CIs were calculated using random-effects model. Results: The combined evidence supports that diabetes was associated with a statistically significant 23% increased risk of breast cancer, especially in postmenopausal women (RR=1.25 95% CI 1.20-1.29). The correlation between diabetes and breast cancer was the most obvious in Europe (RR=1.88,95% CI: 1.56-2.25), followed by America (RR=1.16, 95% CI: 1.12-1.20). In Asia the result was not significant (RR=1.01, 95% CI=0.84-1.21). Diabetes also increased mortality from breast cancer overall (RR=1.44, 95% CI: 1.31-1.58). Conclusions/interpretation: This meta-analysis indicated that diabetes can be considered as a risk factor for breast cancer. In addition, menstruation status as well as geographical distribution can affect the relationship.