Tirzepatide for Weight Loss Intervention in Early-Stage Hormone Receptor Positive/HER2 Negative Breast Cancer

Inclusion Criteria: * Consent: Be willing and able to provide written informed consent for the trial. * Age: Male or Female patients aged 18 years or older. * Breast Cancer Diagnosis: Have hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer previously diagnosed by biopsy. HR status is defined as estrogen receptor (ER) \>10% and/or progesterone receptor (PR) \>10%; HER2 status is defined as immunohistochemistry (IHC) 0 or 1+ or IHC 2+, fluorescence in situ hybridization (FISH) negative. * Stage: Have previously untreated early-stage, clinical or anatomic stage I, II, or III hormone receptor-positive breast cancer. * Definitive Treatment: Have had definitive treatment with curative intent for breast cancer, including surgery, chemotherapy, and radiotherapy as indicated. * Body Mass Index (BMI): Have a BMI of 30 kg/m² or more, or a BMI of 27 kg/m² or more with one weight-related complication (e.g., hypertension, type 2 diabetes, dyslipidemia, obstructive sleep apnea, or cardiovascular disease). * Performance Status: Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. * Cardiac Function: Have a left ventricular ejection fraction (LVEF) of 50% or greater, or greater than the institution's lower limit of normal (LLN), as assessed by echocardiogram (ECHO) or multigated acquisition (MUGA) scan performed at screening. * Organ Function: Demonstrate adequate organ function in screening labs. * Tumor Specimens: Have archived biopsy or surgical tumor specimens available as tumor blocks or unstained slides. Exclusion Criteria: * Other Clinical Studies: Is currently enrolled, or will enroll in, a different clinical study in which investigational therapeutic procedures are performed or investigational therapies are administered while participating in this study. * Stage IV Breast Cancer: Have stage IV, metastatic breast cancer. * Cancer Type: Have HER2-positive or triple-negative breast cancer. * Active Malignancy: Have a concomitant active malignancy. * Performance Status: Have an Eastern Cooperative Oncology Group (ECOG) performance status greater than 2. * Body Mass Index: Have a BMI of less than 27 kg/m². * Type 1 Diabetes Mellitus: Have type 1 diabetes mellitus. * Gastric Emptying Abnormality: Have a known clinically important gastric emptying abnormality (e.g., severe gastroparesis or gastric outlet obstruction) or chronically took drugs that directly affect gastrointestinal motility.