ESR1 and breast cancer: Multivariable-adjusted HRs were significantly higher in patients with stage II (HR, 2.83; 95% CI, 1.90 to 4.20) and stage III (HR, 11.06; 95% CI, 7.07 to 17.30) BC than in those with stage I. With regard to subtype, multivariable-adjusted HRs were higher in patients with TBNC (HR, 3.79; 95% CI, 2.84 to 5.06) and ER−, PR−, and HER2+ BC (HR, 2.32; 95% CI, 1.62 to 3.32) than in those with ER+ or PR+ and HER2− BC.