Hazard ratios of ER+PR+ and ER-PR- tumors for increases in BMI across HRT user categories. All models were restricted to postmenopausal women with information on baseline HRT use and stratified by age at recruitment and study center. HRT never users within BMI tertile1 were used as the reference category. BMI tertile 1: ≤22.5 kg/m2; BMI tertile 2: 22.6 to 25.8 kg/m2; BMI tertile 3: ≥25.9 kg/m2. BMI, body mass index; ER, estrogen receptor; HRT, hormone replacement therapy; PR, progesterone receptor.