Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is an aggressive subtype characterized by overexpression of the HER2 receptor. Anti-HER2 therapies such as trastuzumab and pertuzumab are widely used in clinical practice and have improved patient outcomes; however, their effectiveness and safety profiles may vary across populations. This prospective observational cohort study evaluates the real-world effectiveness, safety, and tolerability of single-agent versus combination anti-HER2 therapy among Egyptian patients with erb-b2 receptor tyrosine kinase 2 (ERBB2)-positive breast cancer. The study aims to describe treatment outcomes and identify factors associated with survival and tolerability in routine clinical practice.