ERBB2 and breast cancer: In this latter regard, exploratory analyses of the largest prospective metformin phase III trial in breast cancer to date (CCTG MA.32) has revealed that the invasive DFS and OS advantages provided by metformin were notably prominent among HER2-positive participants bearing at least one copy of the minor allele (C) of the SNP rs11212617 located near the ATM gene, which has been associated with an increased likelihood of treatment success with metformin in T2D and in HER2-positive breast cancer patients treated with neoadjuvant metformin.