The emerging role of the new aromatase inhibitors in the treatment of breast cancer

The clinical development of aromatase inhibitors in recent years represents a significant addition to our armamentarium for the treatment of postmenopausal patients with hormone receptor-positive breast cancer - both for metastatic disease and in the adjuvant setting. In patients with metastatic disease, third-generation aromatase inhibitors have shown significantly superior efficacy over tamoxifen as first-line hormone therapy. In the adjuvant setting, preliminary results with the use of aromatase inhibitors in ongoing large clinical trials indicate significant gains in disease-free survival rates and in the occurrence of contralateral breast cancer, either alone for 5 years or sequentially after tamoxifen for 2-3 or 5 years. While tamoxifen monotherapy continues to be standard adjuvant therapy for patients with low risk primary breast cancer, postmenopausal patients with higher risk hormone-positive primary breast cancer should also be offered an aromatase inhibitor. Aromatase inhibitors are also prescribed for patients with contraindications to tamoxifen. The optimal sequence and duration of aromatase inhibitor adjuvant therapy as well as its long-term impact on overall survival remain to be established. In general, aromatase inhibitors have a good toxicity profile. Long-term effects such as the risk of osteoporosis need to be better defined.