Lower post-NACT Ki-67 was associated with better breast cancer specific survival (BCSS) in the whole cohort (p < 0.0001), in ER+/HER2− (p = 0.0001) and TNBC (p = 0.0007), but not in HER2+ BC (p = 0.8223). This evidence concerns the gene ESR1 and breast carcinoma.