Switching from tamoxifen to exemestane in localized breast cancer: Four representative case studies

Many postmenopausal women with early breast cancer receive adjuvant tamoxifen therapy to reduce their risk of relapse. Recent clinical trials show that third-generation aromatase inhibitors, given either as initial adjuvant therapy or after treatment with tamoxifen, produce better overall and disease-free survival rates, less risk of local or distant recurrence, and improved safety and tolerability, compared with tamoxifen alone. Aromatase inhibitors block the synthesis of estrogen by aromatase, whereas tamoxifen, an antiestrogen, blocks the binding of estrogen to its receptor. The American Society of Clinical Oncology currently recommends using an aromatase inhibitor in the adjuvant treatment of postmenopausal women with early estrogen receptor-positive breast cancer. Questions regarding the optimal use of aromatase inhibitors remain. The cases presented here are instructive with regard to deciding whether to make the switch to exemestane after tamoxifen.