Tamoxifen has been used to treat both advanced and early stage breast cancer. It has been used for nearly 20 years to treat patients with advanced breast cancer. More recently, it also is being used as adjuvant, or additional, therapy following primary treatment for early stage breast cancer. In other words, estrogen binds to these cells and stimulates them to grow and divide.
Tamoxifen prevents the binding of estrogen.
This stops the cells from growing and in doing so, prevents or delays breast cancer recurrence. Tamoxifen is also known to work through growth factors and the immune system and may provide some benefit even in patients whose tumors are not estrogen sensitive. Results found that premenopausal women, not just postmenopausal women, and those whose breast cancer has spread to the local lymph glands benefit substantially from tamoxifen therapy. Although tamoxifen blocks the effect of estrogen on breast tissue, it acts like a weak estrogen in other body systems. This means that women who take tamoxifen may share some of the beneficial effects of taking estrogen replacement therapy, such as a decreased risk of osteoporosis and a decreased risk of heart disease.