ESR1 and breast cancer: In the study by Guillemette et al. [18] which analyzed 200 AA women with invasive breast cancer and 200 matched controls for the UGT1A1 TA repeat promoter polymorphism, they demonstrated that among pre-menopausal AA women, the association was stronger for estrogen receptor (ER)-negative breast cancers (OR 2.1, 95% CI 1.0–4.2; P = 0.04) than for ER-positive breast cancers (OR 1.3, 95% CI 0.6–3.0; P = 0.5) [18].