Effective Ki-67 Reduction by Pre-Surgery Short-Term Administration of Letrozole in (Hormone-Positive) Breast Cancer

Antigen Ki-67 (histone-based nuclear protein) is a static marker of tumor cell proliferation and growth and is commonly measured to indicate the effect of treatment in breast cancer patients. This single-arm trial study aimed to evaluate the effect of short-term endocrine therapy (letrozole) on Ki-67 levels in menopausal women with early hormone-positive breast cancer who were referred to two university hospitals. Patients with a pre-treatment Ki67 of 5% or less were excluded from the study. Participants (n=25) received oral letrozole (2.5 mg daily) seven days before surgery. Ki-67% on both biopsies and the surgical specimens were measured and compared. The mean age of patients was 62±9.4 (48-83 years). Our result indicated that pre-surgery consumption of letrozole for hormone-positive breast cancer can significantly decrease the of Ki-67 labeling index (23.24±9.74 vs. 16.92±9.55, =0.001 by paired t-test), with no drug-related adverse events.