ESR1 and breast neoplasm: Interestingly, in ER-negative tumors, the pathologic response rate of triple-negative tumors was similar with nontriple-negative tumors (60.0% versus 62.2%, p = 0.885), suggesting that ER might be a more important biomarker in predicting pathologic response of breast tumors to preoperative chemotherapy than PgR and HER2.