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Tamoxifen and Raloxifene Reduce Breast Cancer Risk in Postmenopausal Women

June 17, 2009

Written By Mary Alice Hartsock
Reviewed By Kala Visvanathan, MBBS, FRACP, MHS

Raloxifene was added to the list of recommended chemoprevention strategies to reduce the chances of breast cancer in postmenopausal women at increased risk for developing the disease, according to new guidelines issued by the American Society of Clinical Oncology (ASCO).

Researchers from ASCO, an organization of healthcare professionals and physicians that work together to improve cancer care and prevention, released an update to the 2002 guidelines in the Journal of Clinical Oncology. Announced at ASCO’s 44th Annual Meeting in early June, the new guideline says postmenopausal women may safely take Tamoxifen or Raloxifene for five years to reduce the risk of invasive breast cancer.

About ASCO Guidelines

Doctors use ASCO guidelines to help guide informed decisions about treatment or risk-reduction strategies and to identify important research questions.

To establish guidelines, a group of ASCO members searches for trends among studies that involve a particular treatment or method. If the group discovers similar findings in multiple, well designed studies, it makes consensus recommendations that doctors nationwide use to provide care. To stay on top of new developments, ASCO evaluates and revises its guidelines regularly.

The Analysis

The researchers looked at the results of 17 selected studies on breast cancer risk reduction that had been published since 2002. Their goal was to find out what treatments reduced cases of invasive and noninvasive breast cancer and death from breast cancer while prompting the fewest negative side effects, all in women who had not been diagnosed with breast cancer but who were at increased risk for developing the disease.

Non-invasive breast cancers are located in the ducts of the breast, and invasive breast cancers have traveled outside of the ducts or lobules into the surrounding tissue, lymph nodes or other parts of the body.

To measure the effectiveness of specific medicines at reducing breast cancer risk, these clinical trials compared the outcomes of women who took preventive therapies to those who did not. The studies also compared different chemopreventive methods to one another (for example, the outcomes of women who took Tamoxifen versus the outcomes of those who took Raloxifene).


The findings highlight the hormonal therapies Tamoxifen and Raloxifene (brand name: Evista). These medicines are called selective estrogen receptor modulators (SERMs) and work by targeting cancer cells that have estrogen and progesterone receptors on them. SERMs block the effect of estrogen on breast tissue.

The researchers found that taking tamoxifen for five years reduces the risk of developing breast cancer for at least ten years in premenopausal women (women whose menstrual cycles have not stopped permanently). This benefit was particularly strong at preventing invasive, estrogen receptor-positive breast cancers, or cancers that require the hormone estrogen to grow. Women who were age 50 or younger when they took tamoxifen experienced fewer side effects than older women.

Tamoxifen and Raloxifene, a newer medicine, worked equally well at reducing the risk of developing estrogen receptor-positive invasive breast cancer in postmenopausal women (when periods stop permanently). The researchers pointed out that postmenopausal women who take Raloxifene have a lower risk of blood clots, benign uterine conditions and cataracts compared to postmenopausal women who take Tamoxifen.

The studies were not designed to show whether taking either of these medicines reduces overall risk of death from breast cancer in high-risk women.

The 2009 Guidelines: A Summary

These findings led ASCO to release new guidelines for women at an increased risk of developing breast cancer. The most notable change from the 2002 guidelines is ASCO’s assessment that raloxifene works as well as tamoxifen for reducing risk in postmenopausal women. Tamoxifen remains the best option for premenopausal women. Here are some key points:

  • Tamoxifen may be offered for five years to pre- and postmenopausal women to reduce the risk of invasive, estrogen receptor-positive breast cancer, with benefits lasting up to ten years.
  • Raloxifene may be offered for five years to pre- and postmenopausal women to reduce the risk of invasive, estrogen receptor-positive breast cancer.
  • For postmenopausal women who are not enrolled in clinical trials, the researchers do not recommend the use of an aromatase inhibitor, a medicine that prevents the body from making estrogen or progesterone. (Premenopausal women should not use aromatase inhibitors.)
  • For women who are not enrolled in clinical trials, researchers also do not recommend the use of a retinoid (a type of medicine that regulates cell growth) or a selective estrogen receptor modulator other than Raloxifene or Tamoxifen.
  • Healthcare professionals should help women make informed decisions about their care by thoroughly explaining the risks and benefits of these medicines.

What Do These Guidelines Mean for Me?

If you are at increased risk for developing breast cancer but have never been diagnosed with the disease, talking with your doctor and asking questions can help you decide whether risk reduction medicines are right for you. Your doctor can explain how these guidelines impact your choices and help you weigh the benefits of treatment against potential side effects.

As a postmenopausal woman, these new guidelines give you the option of using Tamoxifen or Raloxifene to reduce your risk. Both medicines can increase your risk of developing joint pain, hot flashes, flu-like symptoms, blood clots or stroke. One study indicated that Raloxifene may have a lower risk of blood clots, benign uterine disorders and cataracts than Tamoxifen. Your medical history, your personal needs and your conversations with your doctor will help inform your choice.

K. Visvanathan, et al. American Society of Clinical Oncology Clinical Practice Guideline Update on the Use of Pharmacologic Interventions Including Tamoxifen, Raloxifene, and Aromatase Inhibition for Breast Cancer Risk Reduction. Journal of Clinical Oncology, 10.1200/JCO.2008.20.5179.

Visit for a detailed description of the ASCO breast cancer risk reduction guidelines.

Learn more about the 2009 ASCO guidelines on hormonal therapy for women at increased risk for breast cancer.