Our results showed a significant prognostic value of metformin compared to other antidiabetic agents in breast cancer patients which is in line with some previous references; the study of He et al at MD Anderson Cancer Center on 1,983 patients with the HER2 positive subtype of breast cancer showed that DM type II was an independent prognostic factor of poor OS in stage II or more of the disease, after adjustment for age, BMI, hormonal receptor status, nuclear grade, and stage. The gene discussed is ERBB2; the disease is breast cancer.