If a woman had a budding cluster of estrogen-dependent breast cancer cells, estrogen replacement could promote the tumor s growth. The accuracy of their measurement is dependent on a timely and efficient collection of the tissue. Tamoxifen, an anti-estrogen drug, interferes with the activity of estrogen. Some breast cancer cells are estrogen sensitive. Estrogen binds to these cells and stimulates their growth and division.
Tamoxifen prevents the binding of estrogen.
This stops the cell 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.