ESR1 and breast carcinoma: Prospective validation of the PEPI and mPEPI 0 biomarker was then tested as a surrogate for RFS in the ALTERNATE trial (Alternate Approaches for Clinical Stage II or II Estrogen Receptor Positive Breast Cancer Neoadjuvant Treatment in Postmenopausal Women: A Phase 3 Study; NCT01953588), which tested whether neoadjuvant fulvestrant or fulvestrant in combination with anastrozole is more effective than anastrozole alone in ER-positive/HER2-negative patients88.