Abstract: Objective The aim of this study was to explore the effect of different molecular types of breast cancer with type 2diabetes.Methods The breast cancer patients with type 2 diabetes admitted to the Affiliated Cancer Hospital of Xinjiang Medical University from January 2000 to December 2019 were retrospectively analyzed as the diabetes group(335 cases),and the non-diabetic patients with breast cancer who visited at the same time were randomly selected as the non-diabetic group(181 cases),the clinicopathologic features of the two groups were compared.The patients were divided into the metformin group(169 cases)and non-metformin group(166 cases)according to whether the diabetic group took metformin orally or not.The Kaplan-Meier method was applied to compare the disease-free survival(DFS)and overall survival(OS)of breast cancer patients with different molecular types.Univariate and multivariate Cox regression models were used to analyze the correlation between clinicopathological features and prognosis.Results The patients in the diabetes group were older than those in the non-diabetes group,and the proportion of postmenopausal patients was higher(P＜0.001).Cox regression analysis showed that tumor size,lymph node metastasis and Ki67 were related to OS and DFS,and menopausal status was an independent factor affecting DFS.Survival analysis showed that the 1-year,3-year,5-year and 10-year disease-free survival and total survival rate were 91.5%,83.3%,81.1%,64.3% and 97%,88.9%,85.1%,72.1% in the non-metformin group,respectively.It was significantly lower than that of metformin group and non-diabetic group(P＜0.05).In 516 cases of breast cancer,299 cases of luminal type breast cancer,141 cases were HER2 positive breast cancer,and 76 cases were triple negative breast cancer.In luminal breast cancer,there was no significant difference in OS and DFS curves among the three groups(P＞0.05);In HER2 positive breast cancer,OS and DFS in the metformin group and non-diabetes group were higher than those the non-metformin group(P＜0.05);In triple-negative breast cancer,DFS in the metformin group was significantly better than in the non-metformin group(P＜0.05).Conclusion Metformin can significantly improve the prognosis of triple-negative,HER2 positive breast cancer patients with type 2 diabetes.

Key words: Breast cancer, Metformin, Type 2 diabetes, Prognostic analysis