Cardiac Side Effects of Systemic Therapy in Early-Stage Breast Cancer

The goal of this observational study is to evaluate cardiac side effects in women with early-stage breast cancer who receive systemic chemotherapy and/or anti-HER2 therapy as part of their standard cancer care. The main questions it aims to answer are: Can changes in Global Longitudinal Strain (GLS) on echocardiography detect early cardiac dysfunction before a drop in left ventricular ejection fraction (LVEF) becomes apparent? Are changes in circulating microRNA levels in the blood associated with early cardiac dysfunction during cancer treatment? Does cardiac dysfunction occur more frequently with anthracycline-containing chemotherapy compared to anthracycline-free regimens? Participants already receiving standard chemotherapy and/or anti-HER2 therapy as part of their routine cancer care will undergo echocardiography (LVEF and GLS), provide blood samples for microRNA analysis, and complete quality of life questionnaires at four time points: before treatment (baseline), and at 3, 6, and 12 months after starting treatment.