The purpose of this study was to assess the difference in disease-free survival between post-menopausal women with hormone receptor-positive early breast cancer who switched from tamoxifen to anastrozole and those who continued on tamoxifen.

Inclusion Criteria:

• Post-menopausal status; age ≤75 years;
• histologically confirmed invasive breast cancer with metastases in the axillary lymph nodes;
• oestrogen receptor status positive or unknown;
• primary treatment (surgery +/- radiotherapy, +/- chemotherapy) completed

Exclusion Criteria:

• Clinical evidence of metastatic disease (including local or remote recurrence, even if the patient appeared to be in complete remission at the time of randomisation).