ESR1 and breast cancer: On multivariate analysis, older age at breast cancer diagnosis (OR for patients aged 40–49 years 0.587, 95% CI: 0.361–0.956; P = 0.032), had ≥2 comorbidities (OR 0.417, 95% CI: 0.238–0.732; P = 0.002) and ER negative (OR 0.624, 95% CI: 0.440–0.886; P = 0.008) were all independent factors for very substantial WHR increase.