ESR1 and breast cancer: Ewertz and colleagues determined that the risk of developing distant metastasis in early-stage breast cancer patients (including ER+, ER− and unknown tumors) with a BMI ≥ 30 kg/m2 increased by 42 to 46% after 10 years, compared to patients with a BMI < 25 kg/m2, and the risk of death due to breast cancer after 30 years was significantly increased by 38% in patients with a BMI ≥ 30 kg/m2 [15, 16].