Developments in endocrine therapy for breast cancer

After the usefulness of ovariectomy in breast cancer patients was demonstrated, endocrine therapy has been one of the most effective treatments of breast cancer. Thereafter, it became clear that estrogen receptors (ERs) existed in the cells of breast cancer. After it was found that ERs could be used as a predictive factor of endocrine therapy for breast cancer, the validity of endocrine therapy has became more certain. Tamoxifen, a major selective estrogen receptor modulator, is the first agent which has shown evidence of improving survival time and disease-free survival time in the treatment of breast cancer, and is the standard treatment, widely used in the treatment of breast cancer all over the world. LH-RH analogue, commonly used in ablation treatment among premenopausal women, produces the same effect as ovariectomy, and recently has shown good results equivalent to chemotherapy in premenopausal breast cancer treatment. Furthermore, aromatase inhibitors as a form of ablation treatment of postmenopausal women have been used recently. In comparison with tamoxifen, aromatase inhibitors have revealed the same or more effective result in postmenopausal breast cancer treatment. In the near future, endocrine mechanisms in the body and the molecular mechanisms of transcription by ER will be more clearly elucidated, and then new kinds of agent and combined therapies for the endocrine treatment of breast cancer will be developed. Currently, many clinical randomized trials are being conducted to examine the effectiveness of new endocrine treatment. Significant changes are occurring in the endocrine treatment of breast cancer.