Endocrine Treatment of Breast Cancer

Endocrine manipulation is a well-recognized treatment modality for breast cancer and better understanding of the role of oestrogen in breast cancer pathogenesis has enabled advances in both early and metastatic breast cancer treatment. Two key pathways are used to reduce oestrogen levels—competition for the oestrogen receptor at the cell surface and by reducing peripheral androgen conversion. Adjuvant therapy with the oestrogen receptor antagonist tamoxifen shows improved disease-free and overall survival when given for ten years. Aromatase inhibitors have shown further benefits in the adjuvant setting either alone (in postmenopausal women) or in conjunction with ovarian suppression (in younger, premenopausal women). Endocrine therapy has had a significant impact on breast cancer treatment, but resistance develops in many patients. The mechanisms for this resistance are being investigated and there are a number of emerging treatment options that may help to overcome resistance although this is a complicated area of research.