To switch or not to switch: should the updated Intergroup Exemestane Study alter our decision?

Adjuvant therapy for breast cancer with aromatase inhibitors improves survival compared with tamoxifen; however, whether they should be given upfront or sequentially after 2-3 years of tamoxifen in estrogen receptor-positive early breast cancer affecting postmenopausal women is unclear. The Intergroup Exemestane Study looked at 4724 postmenopausal patients with estrogen receptor-positive or unknown breast cancer who had been disease free for 2-3 years on tamoxifen and were randomly assigned to switch to exemestane or to continue tamoxifen for the remainder of a 5-year endocrine treatment period. A significant disease-free survival advantage (p = 0.0001) was seen in favor of exemestane, with an absolute benefit of 3.3% by the end of treatment. This trial is the first to show an overall survival advantage for switching in estrogen receptor-positive breast cancer (p