This clinical trial is focused on studying a type of breast cancer known as HER2-positive early-stage breast cancer. This type of cancer is characterized by the overexpression of a protein called HER2, which can promote the growth of cancer cells. The study is exploring a treatment approach that does not involve traditional chemotherapy. Instead, it uses a combination of medications, including Phesgo, which contains the active substances trastuzumab and pertuzumab, and another medication called trastuzumab emtansine (also known as T-DM1). These medications are designed to target and block the HER2 protein, potentially slowing or stopping the growth of cancer cells.

The purpose of the study is to evaluate the effectiveness and safety of this treatment approach in patients who have not received prior treatment for their HER2-positive breast cancer. Participants in the study will receive the medications through injections, with Phesgo being administered under the skin (subcutaneous use) and trastuzumab emtansine being given through a vein (intravenous use). The study will monitor patients over a period of time to assess how well the treatment works in preventing the cancer from returning and to evaluate any potential side effects on the patients’ overall health.

Throughout the study, participants will undergo regular health assessments, including imaging tests like MRI to track the response of the cancer to the treatment. The study aims to provide insights into whether this chemotherapy-free approach can effectively manage HER2-positive early-stage breast cancer while maintaining the patients’ quality of life. The trial will also look at the long-term outcomes, such as the recurrence of cancer and overall survival rates, to determine the potential benefits of this treatment strategy.