ESR1 and breast cancer: Post-menopausal status at breast cancer diagnosis (aHR = 1.69; 95% CI: 1.13–2.53, p = 0.01), Asian ethnicity (aHR = 2.30; 95% CI: 1.03–5.16, p = 0.04), and the ER+/HER2+ subtype (aHR = 2.06; 95% CI: 1.14–3.71, p = 0.02) were significantly associated with a shorter time to BM diagnosis.