ESR1 and breast cancer: Prospective trials and retrospective analyses support this approach with assays like OncotypeDX, Mammaprint, and PAM50 Risk of Recurrence (ROR) approved for use in decisions concerning chemotherapy treatment in the adjuvant setting [[3], [4], [5], [6], [7]].While these gene expression signatures [[3], [4], [5], [6], [7]] are established tools for guiding adjuvant therapy in ER+/HER2– early breast cancer, their role in predicting response to neoadjuvant treatments remains exploratory with limited evidence as outlined in a review from 2025 [8].