Neoadjuvant Endocrine Therapy in Breast Cancer.

Women who suffer from large or locally advanced malignant breast tumors are now commonly treated with preoperative ('neoadjuvant') systemic therapy to improve surgical outcomes and to raise the chances for breast-conserving therapy (BCT). Until recently, chemotherapy was the treatment of choice, and primary systemic endocrine treatment was restricted to medically frail or older women with receptor-positive breast cancer. The development of modern aromatase inhibitors (Als) and their subsequent clinical evaluation in neoadjuvant trials now provides us with an alternative to chemotherapy that is thought to be equally effective, yet considerably better tolerated. Several large prospective trials have compared tamoxifen with the non-steroidal AIs letrozole and anastrozole and the steroidal Al exemestane, with improved outcomes for all AIs in terms of tumor remission and rate of BCT. A number of predictive biomarkers now also allow us to identify those tumors that most likely respond to a certain endocrine regimen.