In advanced disease, aromatase inhibitors as first-line therapy have been shown to extend the time to disease progression (Evidence grade 1). Adjuvant therapy with aromatase inhibitors has been shown to reduce the risk for recurrence after followup of approximately 5 years (Evidence grade 1). No scientific evidence is yet available on long-term effects concerning survival and side effects (beyond 5 years). Only limited evidence is available on the cost effectiveness of using aromatase inhibitors.