Introduction
RS, early-stage HR, breast cancer
SECONDARY, BREAST CANCER
Adjuvant endocrine therapy remains the standard of care for patients with early-stage, HR + breast cancer who can safely omit chemotherapy based on RS results; however, the role of neoadjuvant endocrine therapy remains unclear [The use of genomic assays has significantly impacted how physicians approach adjuvant treatment decisions for women with early-stage, HR + breast cancer; however, data for use in the neoadjuvant setting are limited. Tools to better determine which patients may benefit from neoadjuvant endocrine therapy versus neoadjuvant chemotherapy or upfront surgery followed by chemotherapy remain an unmet need. This secondary pooled analysis of randomized phase II prospective studies re-examines the use of neoadjuvant endocrine therapy among a cohort of premenopausal and postmenopausal patients with early-stage HR + , human epidermal growth factor receptor 2-negative (HER2-) breast cancer randomized to neoadjuvant endocrine therapy or neoadjuvant chemotherapy based on Oncotype DX® assay performed on initial core biopsy specimens. Performance of the 21-gene RS assay on biopsy specimens rather than tissue specimens following excision has demonstrated reliable results [