Effect of Metformin Therapy on Biological Properties and Prognosis of Breast Cancer Patients Complicated with Type-2 Diabetes

Objectives: To evaluate the effect of Metformin therapy on patients of breast cancer with complications of Type-2 diabetes.

Methods: Altogether 102 cases of breast cancer complicated with Type-2 diabetes admitted into Hebei General Hospital from January 2019 to December 2020 were included in the study. They were divided into two groups per whether Metformin was administered in the regimen, namely Metformin group and non-Metformin group. In the meanwhile, 106 cases of breast cancer without Type-2 diabetes admitted in the same period were selected to form a control group. Three groups were compared in terms of general data (incl. age, body mass, family history, menopause or not), clinical staging, tumor histological differentiation, molecular subtyping (Incl. Luminal A, Luminal B, ERBB2+, Basal-like) and prognosis.

Results: Compared with the control group, Metformin group and non-Metformin group presented more patients with an older age and post-menopause state (P<0.05), but the latter two groups were not significantly different (P > 0.05). Patients in Metformin group and non-Metformin group had higher clinical staging and histological differentiation and more cases of Basal-like subtype than those in the control group (P < 0.05), without significant difference between those two groups (P > 0.05). More cases of local relapse, lymphatic and distant metastasis were seen in Metformin and non-Metformin groups, but the differences were not significant (P > 0.05). Both groups had lower 5-year survival rates than the control group (P < 0.05). Metformin group had a higher overall survival rate as well as a survival rate free of other lethal reasons than the non-Metformin group (P < 0.05) but was not significantly different from the control group in the survival rate free of other lethal reasons (P > 0.05).

Conclusions: Type-2 diabetes remains one of the risk factors affecting breast cancer development, progress and prognosis, which could lower the 5-year overall survival rate among breast cancer patients. This is especially evident among menopaused women. Metformin therapy may improve the prognosis of patients of breast cancer complicated with Type-2 diabetes.