The purpose of this study is to describe adherence to anastrozole treatment current practice: cases where anastrozole treatment was halted ( timescale and causes) and estimate the proportion of postmenopausal women with early breast cancer who continue anastrozole therapy after one year follow-up.

Inclusion Criteria:

• Postmenopausal woman with early breast cancer who are prescribed with anastrozole as adjuvant endocrine therapy under the routine clinical practice.
• Histologically or cytologically proven to be HR+(ER or PR +)
• No other concomitant endocrine therapy such as estrogen therapy or selective estrogen receptor modulators
• Provision of written informed consent

Exclusion Criteria:

• Recurrence of breast cancer
• Known hypersensitivity to anastrozole or to any of its excipients
• Any severe concomitant condition which makes it undesirable for the patient to participate in the trial or which would jeopardize adherence with the trial protocol: Amenorrhea<12 months and a intact uterus; Previous inclusion in the present study; Participation in a other clinical study during the last 30 days·
• Women who does not agreed to participate the program

The target study population comprised of postmenopausal women with early breast cancer who were treated with anastrozole for at least one month and are willing to give written informed consent to participate.