Tamoxifen for Women with Breast Ca:Basics

About Tamoxifen

What is tamoxifen?

Tamoxifen (Nolvadex) is a drug in pill form, taken orally, that interferes with the activity of estrogen (a female hormone).

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.

For several years Tamoxifen has also been studied to determine whether it is useful in the treatment of other types of cancer, such as melanoma, endometrial (uterine) cancer, and certain leukemias.

How is tamoxifen used for breast cancer treatment?

As a breast cancer therapy, tamoxifen works against the effects of estrogen, which has been shown to promote the growth of breast cancer cells. It is often called an "anti-estrogen."

As a treatment for breast cancer, the drug slows or stops the growth of cancer cells that are already present in the body.

As adjuvant therapy, tamoxifen has been shown to help prevent the original breast cancer from returning and also prevent the development of new cancers in the opposite breast.

Research has shown that when tamoxifen is used as adjuvant therapy for early stage breast cancer, it not only prevents the recurrence of the original cancer but also prevents the development of new cancers in the opposite breast, in many cases.

Based on these findings, the National Cancer Institute (NCI) sponsored a large clinical trial to determine whether tamoxifen can prevent breast cancer in women who have an increased risk of developing the disease.

Additional benefits of tamoxifen:

While tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other body systems. This means that women who take tamoxifen may share many of the beneficial effects of menopausal estrogen replacement therapy, such as a lowering of blood cholesterol and a slowing of bone loss (osteoporosis).

What are the possible side effects of tamoxifen?

blood clots


eye problems

uterine cancer

other cancers

possible problems with pregnancy

possible menstrual and menopause problems

The National Cancer Institute emphasizes that the benefits of tamoxifen as a treatment for breast cancer are firmly established and far outweigh the potential risk of other cancers.

Some physicians and researchers caution, however, that tamoxifen therapy may not be appropriate for all women who are at increased risk for breast cancer. Consult your physician for more information regarding your individual case.

This content was last reviewed by a University of Maryland Medicine expert on May 14, 2003

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