Given the increasing use of neoadjuvant systemic therapy and genomic assays for early-stage, HR-positive/HER2-negative breast cancer,3,4,19 we sought to quantify the success of NACT or NET for surgical plan (BCS vs. mastectomy) as a function of ER, PR, and Ki-67 expression, the 21-gene RS, or 70-gene risk scores in this patient population, using a large, real-world U.S. oncology database. This evidence concerns the gene ESR1 and breast cancer.