Definition
Antiestrogens are a group of medications that block the effect that estrogen has on the growth of a tumor.
Purpose
For about 20 years, antiestrogens have been used mainly to help prevent and treat breast cancer. Since many breast cancer tumors use hormones to fuel their growth, blocking the hormones limits their ability to grow.
Description
Antiestrogens refer to a group of drugs. Many breast cancer tumors grow due to normal levels of estrogen, a hormone found in the bloodstream. Some patients have tumors that are extra-sensitive to this normal estrogen level. The estrogen attaches to the area on the outside of the tumor cells and sends a signal to the cell that causes it to grow and multiply. Antiestrogens block the protein on the outside wall of the estrogen-sensitive breast cancer cell. By blocking this protein, known as the estrogen receptor, the free-floating estrogen cannot stimulate the cancer cells to grow and multiply any further.
The drug tamoxifen is a common antiestrogen that has proven to have a positive effect in breast cancer patients for both treatment and prevention.
The drug raloxifene is a newer antiestrogen. Early research showed that raloxifene worked against breast cancer with fewer side effects than tamoxifene. In 2003, research also showed that raloxifene may be effective in decreasing new fractures among women with low bone mineral density. However, further clinical trials on raloxifene are needed.
Precautions
Use of tamoxifen has been associated with a number of side effects, including vaginal bleeding, menstrual irregularities, and hypercalcemia (excess calcium in the blood). Most women also experience hot flashes while using the drug. Serious side effects include endometrial cancer and throm boem bolism (blocking of a blood vessel by a particle of a blood clot at the site the blood clot formed). In late 2003, cancer experts were beginning to recommend a new group of drugs called aromatase inhibitors (Arimidex, common name anastrozole or Femara and Novartis, common name letrozole) as an alternative to tamoxifen or following tamoxifen therapy. These drugs fight breast cancer differently, but early research shows they fight it as effectively and with fewer side effects.
Resources
Periodicals
Lewis, Jilene. "Breast Cancer Guidelines Suggest Alternative to Standard Therapy." Drug Topics August 18, 2003: 22.
Pennachio, Dorothy L. "Letrozole Improves Breast Cancer Outlook." Patient Care December 2003: 4.
"Raloxifene Decreases New Fractures in Women with Vertebral Cracks at Baseline." Women's Health Weekly December 4, 2003: 84.
"Revised Guidelines Show Changes for Breast Cancer Treatment." Biotech Week December 24, 2003: 296.
Other
Hormonal Therapy, Breast Cancer Treatment. People Living with Cancer.
—Nancy J. Beaulieu, RPh., BCOP; Teresa G. Odle
