ESR1 and breast cancer: They also found that high BMI immediately before diagnosis (cases) or an index date (controls) was not associated with the risk of ER–, ER+, or TNBC in premenopausal women, but was associated with 31% increased risk of ER+ breast cancer (BMI ≥35 vs. BMI < 25 kg/m2, OR =1.31, 95% CI = 1.02–1.67) and 40% decreased risk of TNBC in postmenopausal women (BMI ≥ 35 vs. BMI < 25 kg/m2, OR =0.60, 95% CI = 0.39–0.93).