Based on the trial information provided, here are the medications involved:

Trastuzumab (labeled with Zirconium-89) is an antibody medication used for imaging purposes. It specifically targets HER2-positive breast cancer cells and helps doctors see where cancer cells are located in the body using a special type of scan called PET/CT.

T-DM1 (also known as Trastuzumab emtansine) is an antibody-drug conjugate medication used to treat HER2-positive breast cancer. It combines trastuzumab with a chemotherapy drug, allowing it to directly target and kill cancer cells that have high levels of HER2 protein on their surface.

HER2-Positive Breast Cancer – A type of breast cancer that occurs when cancer cells have too much of a protein called HER2 on their surface. This form of breast cancer tends to grow and spread more aggressively than other types. The disease begins in the breast tissue and can develop into an advanced or metastatic form, meaning it spreads to other parts of the body. In metastatic cases, cancer cells typically spread through the bloodstream or lymphatic system to form tumors in other organs. The presence of excess HER2 proteins makes these cancer cells particularly active in terms of growth and division. The disease progression can vary from person to person, with some experiencing faster growth rates than others.