Letrozole reduces Ki67 in postmenopausal ER+/HER2- breast cancer after 7-30 days pre-surgeryCan a short course of letrozole before surgery help shrink hormone-sensitive breast cancer?

Status: COMPLETED | Phase: PHASE2 Condition(s): Breast Cancer Female Intervention(s): Letrozole (DRUG) A short pre-surgical non-therapeutic trial involving postmenopausal women with newly diagnosed eR+, HeR2-negative operable breast cancers. After undergoing a core needle biopsy for tissue acquisition, study participants will take a 7- to 30-day (1-4 weeks) course of letrozole in accordance with standard of care. They will then undergo definitive surgical resection of their primary tumor (mastectomy vs lumpectomy) as per standard of care guidelines. Detailed: Patients will receive a prescription for letrozole to be taken orally at a dose of 2.5 mg/day for 7-30 days to allow for variations in surgical scheduling. Patients are to undergo surgical resection of their tumor the day after the last dose of letrozole. Post-treatment tumor biopsies (a goal of 4-6 cores) will be obtained following 7-30 days of letrozole treatment on the day of surgery. Frozen AND formalin fixed core biopsies will be obtained whenever possible. The tissue will be used for study-specific assays as well as routine histopathology. Post-treatment core needle biopsy tissue will be obtained, whenever possible, by the surgeon intraoperatively at the time of routine surgical resection. A formalin-fixed paraffin embedded tumor block from the patient's surgical resection is also r Primary Outcome(s): Measure Ki67 Index in Highly Hormone-dependent Breast Cancers vs. Those That Are Not Enrollment: 61 (ACTUAL) Lead Sponsor: University of Texas Southwestern Medical Center Start: 2018-11-27 | Primary Completion: 2025-02-24 Results posted: 2026-03-16