The Effect of Metformin on Survival Outcomes of Non-Metastatic Breast Cancer Patients with Type 2 Diabetes

Document Type : Research Articles


1 Geisel School of Medicine at Dartmouth, Hanover, NH, USA.

2 Hematology, Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran.

3 The Cancer Research Center of the Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.

4 Department of Hematology-Oncology, Cancer Institute of Iran, Tehran University of Medical Sciences, Tehran, Iran.


Background: There are still inconsistencies about the role of metformin on breast cancer. This study was designed to assess metformin’s effect on the prognosis of female breast cancer patients with type II diabetes. Methods: The present research was carried out as a retrospective cohort study between 2003 and 2014. Breast cancer patients with pre-existing type II diabetes mellitus were included. Overall survival (OS) and relapse-free survival (RFS) were measured as the main endpoints. Kaplan-Meier estimate was used to calculate survival rates. Results: 217 patients were included with a mean age of 53.32±11.10 years. 148 (68.2%) patients were prescribed metformin and 69 (31.8%) took other antidiabetic drugs (non-metformin group). Five-year OS and RFS rates for all patients were 82.5% (95% CI: 76.0%-87.4%) and 71.1% (95% CI: 64.2%-77.0%) respectively. Log-rank test showed that the metformin group had a significant advantage over the non-metformin group in terms of both OS and RFS rates (p  


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