Moreover, an analysis of the ALTTO Phase III randomized trial, which assigned patients with HER2-positive BC to receive 1 year of trastuzumab alone, lapatinib alone, their sequence, or their combination, found that metformin exerted a statistically-significant beneficial effect in those patients with diabetes who had primary HER2-positive and HR-positive BC [47]. Here, ERBB2 is linked to breast cancer.