back to Dr. Reid's Corner Directory

The Effect of Tamoxifen on Prevention of Breast Cancer Recurrence
email this to a friend
Since many of our readers are breast cancer survivors, I thought it would be helpful to summarize some of the new and exciting data coming out for breast cancer treatment. Many women who have breast cancer are treated with a medication called Tamoxifen. This is a drug that resembles estrogen, the female hormone. Estrogen binds to receptors in a cell in a lock and key fashion. When estrogen is present, it binds to the estrogen receptor and stimulates the development of female characteristics such as breast development. Many breast cancers are dependent on the presence of estrogen for their growth and survival. Breast cancer cells can be grown in a dish in the laboratory. When these cells are grown in the presence of estrogen, they are healthy, functional cells; however, when the estrogen is removed, many of these cells will stop growing and die. So, estrogen is critical for growth of many tumor cells.

One way to deprive tumor cells of estrogen is to make a compound that will bind to the estrogen receptor in a lock and key fashion but to alter the compound so that while it fits into the lock, it cannot open the lock. Tamoxifen works in much the same way. Tamoxifen can bind to estrogen receptors and block the function of the receptor. If Tamoxifen is added to breast cancer cells grown in the laboratory, many of these tumor cells will stop growing and die. Even if estrogen is present, the Tamoxifen can successfully compete with the normal estrogen for the binding sites for estrogen found on tumor cells. If Tamoxifen has bound to the estrogen receptor, then normal estrogen cannot get into the receptor to stimulate the normal functions of estrogen. Some breast tumors have lost the estrogen receptor and have adapted to growth without estrogen stimulation. These cancers are estrogen receptor negative and generally do not respond to treatment with Tamoxifen.

A recent study was performed to determine how effective Tamoxifen was in women at risk for recurrent breast cancer. This study demonstrated that daily treatment with Tamoxifen could reduce the incidence of breast cancer by 49%. The use of Tamoxifen is recommended for post-menopausal women with breast cancer cells that have estrogen receptors. The current recommendation is for 5 years of daily treatment. Currently, there is a study comparing Tamoxifen with a similar drug, Roloxifene to determine which drug is more effective.

Tony Reid MD Ph.D
Dr. Reid's Corner
Accredited by the       
Joint Commission