ObjectiveTo explore the effects of metformin on the prognosis of type Ⅰ endometrial carcinoma (EC) patients complicated with type 2 diabetes mellitus (T2DM).MethodsThe clinical data of 45 type Ⅰ EC patients complicated with T2DM (T2DM group) and 147 type Ⅰ EC patients without diabetes mellitus (non-diabetes group) admitted to Qilu Hospital of Shandong University from January 2010 to December 2014 were retrospectively analyzed. The type Ⅰ EC patients with T2DM were divided into two groups, metformin group (n=23, taking metformin to control blood glucose in normal range) and non-metformin group (n=22, taking other hypoglycemic drugs or using insulin to control blood glucose in normal range). The clinicopathological characteristics of T2DM group and non-diabetes group were compared, and the effects of metformin on the prognosis of type Ⅰ EC patients with T2DM were analyzed.ResultsCompared with non-diabetes group, the type Ⅰ EC patients in T2DM group have the older onset age (t=4.331,P<0.001), more complicated with hypertension (χ²=19.252,P<0.001), later surgical pathological stage (χ²=4.588,P=0.032), higher histological grade (χ²=6.069,P=0.048), deeper myometrial infiltration (χ²=7.743,P=0.005) and higher incidence of lymph node metastasis (χ²=4.885,P=0.027). The median progression-free survival (PFS) (47.0 monthsvs.38.0 months) and median overall survival (OS) (52.0 monthsvs. 41.0 months) in metformin group were significantly longer than those in non-metformin group (χ²=10.899,P=0.001;χ²=10.090,P=0.001). There was no significant difference in median PFS (47.0 monthsvs. 46.0 months) and median OS (52.0 monthsvs. 46.0 months) between metformin group and non-diabetes group (χ²=0.791,P=0.374;χ²=0.836,P=0.360). Cox multivariate analysis showed that the risk factors of PFS and OS in type ⅠEC patients were old onset age(OR=2.128, 95%CI: 1.361-3.328,P=0.001;OR=4.502, 95%CI: 1.696-11.954,P=0.003), late surgical pathological stage(OR=2.231, 95%CI: 1.437-3.462,P=0.001;OR=4.005, 95%CI: 1.480-10.836,P=0.006), high histological grade(P=0.001;P=0.017; G2vs.G1:OR=5.660, 95%CI: 3.424-9.357,P=0.001;OR=5.763, 95%CI: 1.666-19.938,P=0.006), deep myometrial invasion(OR=1.531, 95%CI: 1.049-2.235,P=0.027;OR=3.759, 95%CI: 1.890-7.476,P=0.001), positive lymph node metastasis (OR=11.277, 95%CI: 2.774-45.838,P=0.001;OR=8.451, 95%CI: 1.138-62.767,P=0.037)and T2DM (OR=1.897, 95%CI: 1.096-3.281,P=0.008;OR=1.813, 95%CI: 1.043-3.151,P=0.012). Metformin was the protective factor of PFS (OR=0.412, 95%CI: 0.207-0.818, P=0.002) and OS (OR=0.455, 95%CI: 0.228-0.905,P=0.008) in type Ⅰ EC patients with T2DM.ConclusionComplication with T2DM is the negative factor on the prognosis of type Ⅰ EC patients. Intake of metformin can significantly improve the PFS and OS of type Ⅰ EC patients complicated with T2DM and improve the prognosis.