This observational study is restricted to postmenopausal women with hormone-sensitive early breast cancer, who have decided to take prescribed adjuvant use of AIs, anastrozole or letrozole, according to the current product SmPCs. There is no Investigational Medicinal Product (IMP) to be taken in this observational study. The adjuvant AI medication must not have exceeded thirteen weeks. In CARIATIDE (Compliance of ARomatase Inhibitors AssessmenT In Daily practicE through Educational approach), impact of educational material on women's compliance and persistence rates will be evaluated.

Inclusion Criteria:

• Postmenopausal woman with hormone sensitive early breast cancer
• Documented decision of treatment with upfront adjuvant AI (either anastrozole or letrozole) according to current SmPC OR current treatment with AI (either anastrozole or letrozole) according to current SmPC, that has not exceeded thirteen weeks

Exclusion Criteria:

• Upfront adjuvant AI medication which has exceeded thirteen weeks at randomisation
• Concomitant adjuvant treatment with tamoxifen or exemestane
• Previous use of adjuvant tamoxifen or exemestane exceeding thirteen weeks

Postmenopausal women with hormone sensitive early breast cancer that have been prescribed adjuvant AI medication (aromatase inhibitors; anastrozole or letrozole) according to the current product SmPC. The adjuvant AI medication must not have exceeded thirteen weeks of treatment duration.