Additional Study Information: This study is being done to answer the following question: Can participants with HER2-positive breast cancer who have no cancer remaining at surgery (either in the breast or underarm lymph nodes) after 12 weeks of chemotherapy and two HER-targeted therapies eliminate further chemotherapy after surgery? This would be a decrease in the total number of chemotherapy drugs and the amount of chemotherapy typically received to treat this type of cancer. We are doing this study because we want to find out if this approach can enable you to take fewer chemotherapy drugs than the usual approach for your type of breast cancer without compromising your outcome. The usual approach is defined as care most people get for HER2-positive breast cancer. Usual treatment includes additional chemotherapy drugs that might not be necessary, since the HER2-targeted drugs are so effective.