Summary
This phase III trial compares the usual treatment of breast radiation and HER2-targeted drugs following surgery and chemotherapy to using the usual treatment approach without radiation in treating patients with low-risk HER2-positive breast cancer. The usual approach is defined as care most people get for this type of cancer. The usual approach for patients who have undergone surgery, chemotherapy, and HER2-targeted therapy and are not in a study is treatment with radiation therapy to the breast and continuing HER2-targeted therapy. HER2-targeted drugs attach to the HER2 receptor proteins on the surface of breast tumor cells and block the HER2 receptors from receiving growth signals in HER2-positive breast cancer. By blocking the growth signals, HER2-targeted drugs can slow or stop the growth of HER2-positive breast cancer. Radiation therapy uses high energy sources of radiation to kill tumor cells and shrink tumors. The usual approach for patients who have undergone surgery, chemotherapy, and HER2-targeted therapy and are not in a study is treatment with radiation therapy to the breast and continuing HER2-targeted therapy. Omitting radiation from the usual treatment approach may avoid the potential short-term and long-term risks of radiation in patients with low-risk HER2-positive breast cancer and may have the same effect as the usual approach in preventing cancer from coming back (recurrence ).