An estimated 45 agents were in clinical trials in 1997 for breast cancer. Adjuvant therapy, either hormonal or chemotherapeutic have become standardized in the treatment of primary breast cancer. Dose-intensity has shown higher response rates than traditional chemotherapy courses. Hormonal manipulation is believed to have an impact due to breast tissue retaining its former hormonal sensitivity. Tamoxifen is an antiestrogen that inhibits production of an epithelial growth factor and stimulates production of an inhibitory growth factor, both of which are ultimately detrimental to the cancer cells.
Tamoxifen occupies the estrogen receptor site, preventing estrogen from binding.
While this conveys apparent benefit in controlling tumors expressing estrogen receptors on their surface, it also imparts cardiovascular benefit and halts osteoporosis like estrogen does in post-menopausal women. The standard dose is 20mg a day orally and is indicated for up to five years unless disease progression is evident. All of these agents are presently indicated for the treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy. Additional agents are under study, and are not fully understood, nor is their place in therapy fully realized at present. Since the 1970 s, cytotoxic agents have been used to treat breast cancer.