ESR1 and breast cancer: However, Kaplan-Meier analysis of different molecular subtypes showed that chemotherapy delay is insignificant only in HER2 positive subtype (for women with ER+/-HER2+ type breast cancer), while it statistically significantly reduced survival for women with hormone and HER2 receptor negative tumor (ER-HER2-) and hormone receptor positive (ER + HER2-) tumours.