This research is being done to see how safe and effective the use of the study drug
Ado-trastuzumab (T) emtansine (DM1), T-DM1, and standard of care chemoradiation are when used
together in treating HER2-positive salivary gland cancer. It will also examine the
effectiveness of study drug Ado-trastuzumab (T) emtansine (DM1) on cancer recurrence.