ESR1 and breast cancer: In a meta-analysis by Houssami et al., the pCR rate by NAC was reported to be 8.3%, 18.7%, 38.9%, and 31.1% in estrogen receptor–positive (ER +)/HER2-negative (HER2–), ER +/HER2 +, ER-negative (ER–)/HER2 +, and TN breast cancer, respectively, showing a correlation between pCR rate and breast cancer subtype [5].