Estrogen receptor-positive breast cancer cells rely mainly on the growth of estrogen. Pre-menopausal women, estrogen mainly come from the ovary; and post-menopausal women, estrogen is mainly derived from fat, muscle and liver tissues endures through Aromatase role will be androgen into estrogen. Therefore, by inhibiting aromatase, can reduce estrogen levels, so as to achieve therapeutic effect.
First-generation aromatase inhibitors because of side effects, and inconvenient to use, has now been eliminated; second-generation aromatase inhibitors, although the side effects become smaller, but its efficacy is not superior to tamoxifen (tamoxifen), are no longer used; gradually been developed in recent years, the third-generation aromatase inhibitors such as letrozole, anastrozole, exemestane, due to be highly selective in inhibiting aromatase, the specificity, At the same time side effects are significantly reduced.
In the early postoperative adjuvant endocrine therapy for breast cancer research, there have been four large-scale international randomized clinical trials, and compares anastrozole, letrozole, exemestane and tamoxifen efficacy. The results showed that post-menopausal patients with receptor-positive breast cancer after surgery, direct use of anastrozole and letrozole is superior to tamoxifen; in the use of tamoxifen after 5 years, and then to five years of letrozole compared with tamoxifen alone 5 years , significantly better efficacy; in the use of tamoxifen after 2-3 years in favor of exemestane, or anastrozole 2-3 years, is better than tamoxifen alone for 5 years. With advanced breast cancer, clinical studies have confirmed that, as a second-line drugs, third-generation aromatase inhibitors, the efficacy is superior to megestrol acetate, is better than tamoxifen. Therefore, aromatase inhibitors in postmenopausal receptor-positive breast cancer, especially in lymph node-positive patients, adjuvant endocrine therapy the new standard drugs, has been widely welcomed.
