Organization issues update on use of adjuvant hormone therapy

The American Society of Clinical Oncology (ASCO) has issued updated guidelines on the use of aromatase inhibitors (AIs) and tamoxifen for women with hormone receptor-positive breast cancer.

Under the new guidelines, most postmenopausal women with hormone receptor-positive breast cancer should consider taking AIs at some point during the course of therapy, either as initial adjuvant therapy or after 2 to 3 years of tamoxifen.

Women can take up to 5 years of AI therapy, which can be started after 5 years of tamoxifen therapy, in which case a woman could receive up to 10 years of hormone treatment to reduce the risk of recurrence. AIs are effective only in postmenopausal women.

The new guidelines are based on an examination of 12 prospective randomized trials that compared tamoxifen and 1 of the 3 available AIs-anastrozole, letrozole, and exemestane-as part of adjuvant breast cancer therapy.

The studies showed that use of an AI, either alone or combined with tamoxifen therapy, reduced the risk of recurrence and improved disease-free survival compared with tamoxifen alone. Specifically, AI use reduced the risk of in-breast recurrence and cancer in the opposite breast and also reduced the risk of distant metastases.

The trials also showed that although tamoxifen and AIs work differently, most women have relatively mild adverse effects with either class of drug. No important differences in effectiveness among the 3 AIs were found.

Burstein HJ, Prestrud AA, Seidenfeld J, et al. American Society of Clinical Oncology Clinical Practice Guideline: update on adjuvant therapy for women with hormone receptor-positive breast cancer. J Clin Oncol. 2010:doi:10.1200/JCO.2009.26.3756.