APOLLO(Aromatase Inhibitor Patient cOmpLiance Program With qoL Questionaire)

Inclusion Criteria: * Provision of written informed consent * Patients with early breast cancer who are scheduled to receive first-line adjuvant endocrine therapy with aromatase inhibitor under the routine clinical practice * Histologically or cytologically proven to be HR+(ER or PR +) * Postmenopausal woman, defined as a woman fulfilling any of the following criteria(by the local guideline): * Age \>= 50 years * Age \< 50 years with amenorrhoea \> 12 months and an intact uterus * FSH levels within postmenopausal range (over 30-40 IU/ml), or * Having undergone a bilateral oophorectomy. * No other concomitant endocrine therapy such as estrogen therapy or selective estrogen receptor modulators Exclusion Criteria: * Recurrence of breast cancer * Known hypersensitivity to aromatase inhibitor or to any of the excipients * Any severe concomitant condition which makes it undesirable for the patient to participate in the trial or which would jeopardize compliance with the trial protocol * Previous inclusion in the present study * Participation in a clinical study during the last 30 days