ESR1 and breast cancer: Of them, 94.2% (49/52) patients completed 4 TC cycles and had an overall pCR rate of 16.3% (8/49); patients with luminal A-like breast cancer (ER+, Ki67 index < 20%, HER2 negative) had a pCR rate of 0% (0/12); patients with luminal B-like breast cancer (ER+, Ki67 index > 20%, HER2 negative) had a pCR rate of 4.3% (1/23); patients with TNBC had a pCR rate of 50.0% (7/14); almost all of the pCR occurred in TNBC breast cancer patients [34].