ESR1 and breast cancer: High ESR1 methylation was associated with a worse prognosis of disease‐free survival (DFS) (HR = 1.844, 95% confidence interval [CI]: 1.011 to 3.363, p = 0.0460) and OS (HR = 1.746, 95% CI: 1.030 to 2.963, p = 0.0386) in all BC patients (Figure 5K and L).