What is tamoxifen?
Tamoxifen (Nolvadex®) is a
medication in pill form that has been used for 25 years to treat breast cancer
in women and men. Tamoxifen is one of the most common hormonal therapy drugs. It
has been shown to decrease the chance of recurrence in some early-stage breast
cancers and to prevent the development of cancer in the opposite breast.
Tamoxifen also slows or stops the growth of cancer cells present in the body.
There are an estimated 29 million women at increased risk for
breast cancer in this country, and tamoxifen may offer another alternative to
watchful waiting or prophylactic (preventative) mastectomy.
How does tamoxifen affect breast cancer?
Tamoxifen is classified as a selective estrogen receptor
modulator (SERM) and works as an anti-estrogen: While the hormone estrogen
promotes the growth of breast cancer cells, tamoxifen works by blocking estrogen
from attaching to estrogen receptors on these cells. By blocking the estrogen
receptors, it is believed that the growth of the breast cancer cells will be halted.
Can tamoxifen prevent breast cancer?
In 1998, the National Cancer Institute (NCI) funded a large
research study designed to determine whether tamoxifen would reduce the
incidence of breast cancer in healthy women known to be at high risk. The
National Surgical Adjuvant Breast and Bowel Project (NSABP) conducted the study,
known as the Breast Cancer Prevention Trial (BCPT). The results of the trial
showed a 50 percent reduction in both invasive and non-invasive breast cancer in
the treated women.
Tamoxifen has also been shown to substantially reduce the risk
of developing invasive breast cancer in women who have had ductal carcinoma in
situ (DCIS), DCIS is a group of cancer cells that involve only the lining of a
duct and have not spread to other tissues in the breast.
When is tamoxifen prescribed?
Tamoxifen should be prescribed only for women at high risk for
breast cancer and after a complete medical evaluation of a woman’s individual
risk factors. These risk factors include the woman’s age, personal health
history and family history of breast cancer.
However, tamoxifen may not be suitable for all women at high
risk of developing the disease. An informed discussion between a woman and her
physician is essential in determining the appropriateness of this treatment
option. Women who should definitely not use tamoxifen include pregnant women,
women planning to become pregnant, women with a history of blood clots or stroke
or those who are taking anticoagulants.