ATOP TRIAL: T-DM1 in HER2 Positive Breast Cancer

This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational drug to learn whether the drug works in treating a specific disease. "Investigational" means that the drug is being studied and research doctors are trying to find out more about it-such as the safest dose to use and the side effects it may cause. The purpose of this research study is to examine the long-term benefits of T-DM1 with regard to breast cancer and take a closer look at the side effects experienced by participants receiving T-DM1. The FDA (the U.S. Food and Drug Administration) has not approved T-DM1 for use in patients with stage I, II, or III breast cancer, but it has been approved for use in advanced, previously treated, HER2-positive breast cancer. T-DM1 is an antibody-drug conjugate; it is made up of an antibody (trastuzumab) linked to a cytotoxic drug, DM1 (chemotherapy). T-DM1 functions as a targeted cancer therapy because it targets HER2-positive breast cancer cells directly, limiting exposure of the rest of the body to chemotherapy. More specifically, the trastuzumab in T-DM1 first binds to the HER2 protein on the surface of the breast cancer cells and the DM1 then enters the cells and can cause them to die, preventing tumor growth