3.1.1 All postmenopausal women with histology-confirmed invasive primary breast cancer, who have completed primary surgical or radiotherapy (XRT) with or without adjuvant chemotherapy and are candidates to receive adjuvant therapy with aromatase inhibitors will be screened for eligibility. Postmenopausal is defined as satisfying one or more of the following criteria: having had bilateral oophorectomy; aged more than 60 years; or aged 55-59 years with an intact uterus and amenorrheic for at least 12 months; or if amenorrheic for less than 12 months (after receiving hysterectomy, hormone therapy or chemotherapy).