- Endocrine therapy* (all postmenopausal and some premenopausal** patients who have endocrine-responsive tumors***): Patients are stratified according to participating center, risk group (GHR/CHR vs GHR/CLR vs GLR/CHR vs GLR/CLR), adjuvant chemotherapy (no vs nonrandomized vs arm I vs arm II), endocrine sensitivity (both ER and PR positive vs either ER or PR positive), age (< 50 years vs at least 50 years), HER2/neu status (positive vs negative vs unknown), method of axillary evaluation (sentinel only vs dissection), and type of surgery (mastectomy vs quadrantectomy/tumorectomy). In case PR is unknown, the patient will be stratified to the HR negative group if ER is negative, and to the HR positive group if ER is positive.