Treatment With Metformin Is Associated With Higher Remission Rate in Diabetic Patients With Thyroid Cancer

Context: Clinical trials demonstrated that metformin increases the efficiency of systemic therapy in cancer patients. Objective: We examined whether the efficacy of conventional treatment of differentiated thyroid cancer (DTC) is affected by therapy with metformin in diabetic patients. Design: We compared the rate of complete response (CR) between diabetics who were treated with metformin (group MF+; n = 34) or not treated (group MF−; n = 21) and control nondiabetic patients (group C; n = 185). We also examined the effects of metformin on DTC cells in vitro. Results: The groups were comparable in terms of age, sex, body mass index, diabetes management, frequencies of multifocal tumor growth, extrathyroidal extension, and locoregional and distant metastases. Tumor size was significantly smaller in the MF+ group compared with the MF− and C groups (1.37 ± 0.97 vs 2.44 ± 1.49 vs 2.39 ± 1.73 cm, respectively; P = .026). A multivariate model revealed that extrathyroidal extension (P = .018), distant metastases ...