Can a simple ratio predict breast cancer treatment success?

This study looks at whether a very high level of a protein called HER2 (measured by the HER2/CEP17 ratio) affects how well breast cancer patients do after treatment with a combination of two targeted drugs (trastuzumab and pertuzumab). Researchers will review medical records of 300 adults with early-stage HER2-positive breast cancer who had surgery and this dual therapy. The goal is to see if those with ultra-high HER2 levels have different outcomes, like time until cancer returns.