Authors' objectives:

This review aims to assess the extent to which aromatase inhibitors are more effective than anti-estrogen drugs in adjuvant treatment of breast cancer and as first-line therapy for advanced breast cancer in postmenopausal women.

Authors' results and conclusions: Advanced disease: Three randomized studies, including slightly over 1 800 patients in total, have compared aromatase inhibitors as first-line therapy for advanced breast cancer versus antiestrogen therapy (tamoxifen). Results from two of the studies have shown that the time to disease progress was 3 to 5 months longer in the group treated with aromatase inhibitors. The third study, however, reported no difference. Adjuvant therapy: A randomized study of slightly more than 9 000 women, which compared aromatase inhibiting therapy (anastrozole) to tamoxifen therapy, showed after 68 months of followup that the group treated with anastrozole experienced 18.4 percent recurrence compared to 20.9 percent recurrence in the group treated with tamoxifen. These results provided a basis for approving anastrozole for adjuvant therapy in postmenopausal women with estrogen-receptor-positive breast cancer. A study that compared the aromatase inhibitor exemestane against tamoxifen showed, after 3 years of followup, results favoring the study group. Furthermore, a study that randomized just over 5 000 patients, after 5 years of tamoxifen therapy, to treatment with the aromatase inhibitor letrozole versus placebo showed an improvement in disease-free survival for the aromatase inhibitor treatment group. It is too early to assess the effects on overall survival, since these studies have not yet recorded a sufficient number of events (deaths). Complications and side effects: The most common side effects associated with aromatase inhibitors are hot flushes, nausea, and genital dryness. Given the short followup times to date, fewer side effects have been reported with aromatase inhibitors than with tamoxifen, e.g., reduced risk for thromboembolic complications. However, adjuvant treatment with aromatase inhibitors affects bone mineral density and is associated with a higher incidence of fractures. Followup regarding long-term skeletal effects needs to be continued.

Authors' recommendations: 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.

Authors' methods: Review

Project Status: Completed

URL for project: http://www.sbu.se/Published

Year Published: 2005

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Sweden

Organisation Name: Swedish Agency for Health Technology Assessment and Assessment of Social Services

Contact Address: P.O. Box 3657, SE-103 59 Stockholm, Sweden. Tel: +46 8 4123200, Fax: +46 8 4113260

Contact Name: registrator@sbu.se

Contact Email: registrator@sbu.se

Copyright: Swedish Council on Technology Assessment in Health Care (SBU)