To our knowledge, this is the first prospective study evaluating the relationship between the ATM SNP rs11212617 C allele, which has been associated with an increased likelihood of metformin treatment success in T2D (1, 3, 5), and the clinical benefit of adding metformin to well-established neoadjuvant treatment regimens in breast cancer patients. This evidence concerns the gene ATM and type 2 diabetes mellitus.