ESR1 and breast cancer: In middle-aged and older women, the impact of secondary BC on BCSS was most pronounced among women who have hormone receptor positive disease (ER/PR positive, HER-2 negative), the most common tumor subtype in this age group.7,29 We also observed that middle-aged women with HER-2 positive or triple negative tumors had fewer differences in BCSS between primary and secondary BC than hormone receptor positive disease, which might stem from the already decreased BCSS seen in these subtypes in primary BC compared with hormone receptor positive BCs.