PAM50 subtype, which is the basis for the commercial assay Prosigna, is prognostic in ER-positive BC,30,31 and emerging evidence indicates an association with ET sensitivity.21 In ALTERNATE, A+F led to a significantly greater Ki67 suppression and decreased likelihood of maintaining Ki67 greater than 10% at week 4 in LumB vs LumA tumors. This evidence concerns the gene MKI67 and breast cancer.