ESR1 and breast cancer: However, this is solely due to patients with ER+ breast cancers (HR = 0.78, 95%CI = 0.72–0.85, p = 9.0 × 10−9; Table 1), as there is no univariate prognostic strength for ER- breast cancer patients (HR = 0.99, 95%CI = 0.88–1.12, p = 0.8796; Table 1).