A Study to Evaluate the Safety of Adjuvant Treatment With Exemestane Following Previous Treatment With Tamoxifen in Postmenopausal Women With Estrogen Sensitive Primary Breast Cancer

Inclusion Criteria: * Postmenopausal patients * Patients with early breast cancer after adequate loco-regional treatment and eventual adjuvant chemotherapy, treated with tamoxifen for 2-3 years OR treated with tamoxifen for 2-3 years and consecutive exemestane treatment, provided the total duration of endocrine treatment is less than 5 years * Estrogen receptor positive breast cancer patients * Patients who remain free from disease following treatment with tamoxifen Exclusion Criteria: * Patients taking other drugs for the adjuvant treatment of breast cancer * Patients taking hormone replacement therapy * Donation of blood or blood products for transfusion during the 30 days prior to initiation of treatment with study drug, at any time during the program or 30 days after completion of treatment