The purpose of the study is to evaluate quality of life (Qol) in postmenopausal HR (+) EBC patients during adjuvant AIs treatment in terms of: the change of the trial outcome index (TOI) of the FACT-B questionnaire from baseline to 24 months. This study will recruit approximately 500 patients from 21 sites in China. The patients should be postmenopausal HR (+) EBC patients who have already start adjuvant AIs treatment but within 7 days.

Inclusion Criteria:

• Postmenopausal women ≤ 70 years old, with histologically proven HR (+) early breast cancer.
• Undergoing upfront AIs adjuvant treatment within 7 days.

Exclusion Criteria:

• Patients who disagree to participate this study
• Patients who, for whatever reason (eg, confusion, infirmity), are unlikely to comply with trial requirements.
• The AIs have not been approved by SFDA for the indication of upfront adjuvant endocrine therapy in early breast cancer.

The eligible patients will be recruited when they start their upfront AIs adjuvant treatment within 7 days.