BELIEVE is a translational research study that aims to collect samples of breast cancer tissue and blood from individuals undergoing breast cancer treatment (such as chemotherapy, targeted therapy and immunotherapy) before surgery. In certain cases, MRI scans and stool samples will also be obtained before and during treatment. The samples collected from this study will be used for molecular and genetic research to understand why some cancers respond very well to anticancer treatments, and some do not, develop novel ways of accurately measuring response during treatment, as well as identify which patients are at a higher risk of the cancer coming back after surgery.