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CancerQuest > Introduction to Patient Information > An Introduction to Cancer Treatments > Introduction to Hormonal Cancer Treatments > Selective Estrogen Receptor Modulators (SERMs)

Selective Estrogen Receptor Modulators (SERMs)

Many individuals with breast cancer have tumors driven to grow by the naturally occurring hormone, estrogen . One of estrogen's normal activities is to cause the proliferation of cells in the breast and uterus; each month new cell linings must be created for the milk glands (breast) and the endometrium (uterus). In some breast cancer patients this normal expression of estrogen contributes to the growth and division of the cancer cells. For these patients, treatment with selective estrogen receptor modulators (SERMs), also known as anti-estrogens, is appropriate.

The drugs work by causing changes in the shape of estrogen receptors (ER), preventing the action of the hormone. The drugs only affect a subset of the cells capable of responding to estrogen but the precise mechanism of this selectivity is not yet known. It is this selective action that has earned the drugs their name. The blockage of estrogen in the target cells causes changes in gene expression and alters the behavior of the cells, preventing cell division.⁽¹⁾

In 1992, tamoxifen became the first SERM to be used for the treatment of breast cancer. While it does decrease estrogenic effects in the breast, it unfortunately has a pro-estrogenic activity in the uterus, causing a rise in uterine cancer for tamoxifen-treated breast cancer patients.⁽²⁾

Recently, next generation SERMs such as raloxifene have been investigated for their potential as breast cancer treatments. This drug appears to have anti-estrogenic effects in both breast and uterine tissues. Two six-month studies conducted in 1999 show that raloxifene does not stimulate endometrial growth. Studies of 969 post-menopausal women taking raloxifene showed that treatment with the drug did not lead to a significant increase in endometrial thickness as compared to women taking a placebo.⁽³⁾

The results of the STAR trial showed that raloxifene was equal to tamoxifen for the prevention of invasive breast cancer in post-menopausal women and had somewhat improved side effects.^{(4) (5) (6)}

"On September 13, 2007, the U. S. Food and Drug Administration approved raloxifene hydrochloride tablets (EVISTA, Eli Lilly and Company) for reduction in the risk of invasive breast cancer in postmenopausal women with osteoporosis and in postmenopausal women at high risk for invasive breast cancer."⁽⁷⁾⁽⁸⁾

Watch an animation showing how these drugs work.

Tamoxifen (Nolvadex®)
Raloxifene (Evista®)
Toremifene (Fareston)

References for this page:

1. Katzenellenbogen B, Katzenellenbogen J. "Defining the "S" in SERMs". Science (March 29, 2002). 295: 2380-2381. [PUBMED]
2. Shang, Y Brown, M. "Molecular Determinants for the Tissue Specificity of SERMS". Science (March 29, 2002). 295: 2465-2468. [PUBMED]
3. Scott J, Da Camara C, Early J. "Raloxifene:A Selective Esrogen Receptor Modulator". American Family Physician (September 1999). [http://www.aafp.org/afp/990915ap/1131.html]
4. Vogel VG; Costantino JP; et. al.; for the National Surgical Adjuvant Breast and Bowel Project (NSABP). Effects of Tamoxifen vs Raloxifene on the Risk of Developing Invasive Breast Cancer and Other Disease Outcomes: The NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 Trial. JAMA. 2006;295:2727-2741. Published online June 5, 2006. [PUBMED]
5. Land SR; Wickerham DL; et.al. Patient-Reported Symptoms and Quality of Life During Treatment With Tamoxifen or Raloxifene for Breast Cancer Prevention: The NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 Trial. JAMA. 2006;295:2742-2751. Published online June 5, 2006. [PUBMED]
6. Vogel VG The NSABP Study of Tamoxifen and Raloxifene (STAR) trial. Expert Rev Anticancer Ther. 2009 Jan;9(1):51-60. Erratum in: Expert Rev Anticancer Ther. 2009 Mar;9(3):388. [PUBMED]
7. FDA News Release on Raloxifene. Accessed 12/01/2009 [http://www.fda.gov/AboutFDA/CentersOffices/CDER/ucm129243.htm]
8. "Understanding Estrogen Receptors, Tamoxifen and Raloxifene". National Cancer Institute. [http://newscenter.cancer.gov/sciencebehind/estrogen/estrogen00.htm]