The purpose of this study is to compare the effectiveness of 6 months of HER2-targeted medications (trastuzumab with or without pertuzumab) versus 12 months of HER2-targeted medications at reducing the risk of breast cancer coming back or death in patients with early-stage HER2+ breast cancer who had a pCR after preoperative chemotherapy combined with trastuzumab.
This study will help the study doctors find out if this different approach is better, the same, or worse than the usual approach.