ESR1 and bone metastasis: In multivariate analysis, the odds of the first DM site being bone metastasis were significantly increased by ER positivity (p < 0.0001; OR = 5.2, 95% CI 2.3–11.8) and N1 stage compared to N0 (p = 0.05, OR = 3.0, 95% CI 1.4–6.4), as well as significantly decreased for patients positive for HER2 irrespective of ER status (p = 0.04; OR = 0.4, 95% CI 0.2–0.98) and those that underwent the group of “other” chemotherapy regimens, including paclitaxel, docetaxel and TC (p = 0.03; OR= 0.15, 95% CI 0.27–0.84).