This phase III trial studies how well trastuzumab emtansine (T-DM1) and tucatinib work in preventing breast cancer from coming back (relapsing) in patients with high risk, HER2 positive breast cancer. T-DM1 is a monoclonal antibody, called trastuzumab, linked to a chemotherapy drug, called DM1. Trastuzumab is a form of targeted therapy because it attaches to specific molecules (receptors) on the surface of cancer cells, known as HER2 receptors, and delivers DM1 to kill them. Tucatinib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Giving T-DM1 and tucatinib may work better in preventing breast cancer from relapsing in patients with HER2 positive breast cancer compared to T-DM1 alone.

This trial studies how well paclitaxel, trastuzumab, and pertuzumab work in eliminating further chemotherapy after surgery in patients with HER2-positive stage II-IIIa breast cancer who have no cancer remaining at surgery (either in the breast or underarm lymph nodes) after pre-operative chemotherapy and HER2-targeted therapy. Drugs used in chemotherapy, such as paclitaxel, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Trastuzumab and pertuzumab are both a form of “targeted therapy” because they work by attaching themselves to specific molecules (receptors) on the surface of tumor cells, known as HER2 receptors. When these drugs attach to HER2 receptors, the signals that tell the cells to grow are blocked and the tumor cell may be marked for destruction by the body’s immune system. Giving paclitaxel, trastuzumab, and pertuzumab may enable fewer chemotherapy drugs to be given without compromising patient outcomes compared to the usual treatment.

This Phase III Trial evaluates whether breast conservation surgery and endocrine therapy results in a non-inferior rate of invasive or non-invasive ipsilateral breast tumor recurrence (IBTR) compared to breast conservation with breast radiation and endocrine therapy.

This phase II trial studies how well radiation therapy with or without olaparib works in treating patients with inflammatory breast cancer. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. Olaparib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. It is not yet known whether radiation therapy with or without olaparib may work better in treating patients with inflammatory breast cancer.