Pimentel I, Lohmann AE, Ennis M, et al. - Researchers carried out a Phase II randomized trial of chemotherapy plus metformin compared with placebo in metastatic breast cancer (MBC). Non-diabetic MBC patients were randomly assigned on 1st to 4th line chemotherapy to receive metformin 850 mg PO BID or placebo BID. Forty individuals were randomized with a mean age of 55 vs 57 years and ER/PR positive BC in 86.4% vs 83.3% off metformin vs placebo, respectively. Data reported that grade 3–4 toxicity occurred in 31.8% (metformin) vs 58.8% (placebo). Metformin demonstrated no significant impact on response rate, progression-free survival or overall survival in this population. The use of metformin with chemotherapy in non-diabetic MBC patients was not supported in this analysis.