The hormonal therapy medicines tamoxifen and Evista (chemical name: raloxifene) are approved by the U.S. Food and Drug Administration to be used to reduce breast cancer risk in post-menopausal women at higher-than-average risk. New guidelines from the American Society of Clinical Oncology (ASCO) also recommend both of these medicines to reduce risk in post-menopausal women at high risk.
ASCO is the world's largest organization of cancer doctors and researchers. ASCO guidelines give doctors recommendations for treatments that are supported by much credible research and experience. ASCO guidelines released in 2002 recommended only tamoxifen to lower breast cancer risk in high-risk, post-menopausal women. After those guidelines were put out, four large studies showed that Evista also effectively lowers breast cancer risk in high-risk, post-menopausal women. Based on this research, the ASCO guidelines have been updated to include both Evista and tamoxifen as recommended treatments to lower risk in high-risk, post-menopausal women.
Both tamoxifen and Evista are selective estrogen receptor modulators (SERMs). SERMs can lower the risk of hormone-receptor-positive breast cancer in post-menopausal women AND improve bone health. SERMs block the action of estrogen in breast cells and certain other cells in the body by sitting in the cells' estrogen receptors. SERMs don't affect all estrogen receptors the same way because they're selective (as the name says). While tamoxifen blocks estrogen's action on breast cells, it activates estrogen's action in bone and liver cells, so tamoxifen also can help stop bone loss after menopause and help lower cholesterol. Hormone-receptor-negative breast cancers don't have estrogen receptors, so they aren't affected by SERMs. Neither tamoxifen nor Evista lowers the risk of hormone-receptor-negative breast cancer.
Both tamoxifen and Evista are pills taken by mouth and each is taken for 5 years to reduce breast cancer risk in high-risk, post-menopausal women. Evista also is approved to strengthen bones and reduce the risk of osteoporosis in post-menopausal women, regardless of breast cancer risk. So the new ASCO guidelines say that Evista -- but not tamoxifen -- can be taken for more than 5 years by post-menopausal women with osteoporosis and a higher-than-average risk of breast cancer.
Because tamoxifen and Evista work in the same way, they have the same possible treatment risks and side effects, including:
The likelihood or severity of any side effect seems to be different with each medicine. In one study women taking tamoxifen were more likely than women taking Evista to have bothersome hot flashes and sweating, while women taking Evista were more likely to have joint pain.
Because of the risk of potentially life-threatening blood clots, tamoxifen and Evista are NOT recommended for women who have had a serious blood clot or are at high risk for blood clots.
If you're a postmenopausal woman and believe your breast cancer risk is higher than average, talk to your doctor about your risk and about steps you can take to lower that risk. Your doctor can help you assess your breast cancer risk. Then you and your doctor can decide if medicine to lower your risk is appropriate for you and your unique situation. You and your doctor may use the National Cancer Institute's risk calculator tool. This online tool uses your personal and family medical history to objectively assess your breast cancer risk.
If lowering your risk with medicine is a good option for you, the new ASCO guidelines give you and your doctor confidence in choosing either tamoxifen or Evista. Which one you choose will depend on a number of factors, including possible side effects, your bone health, and other aspects of your medical history. Together, you and your doctor can choose the risk-lowering medicine that makes the most sense for you.
RIDGEWOOD, N.J., May 26 (MedPage Today) -- Postmenopausal women at increased risk for breast cancer may benefit from taking either tamoxifen or raloxifene, according to an updated guideline from the American Society of Clinical Oncology.
The previous guideline, issued in 2002, recommended only tamoxifen for reducing risk.
However, four randomized prospective trials since then have found consistent risk reductions with raloxifene as well, so that agent has been added as an option, according to Kala Visvanathan, M.D., of Johns Hopkins, and colleagues.
They published the guideline online, ahead of print, in the Journal of Clinical Oncology.
Key components of the new guidelines are as follows:
Women who are eligible for tamoxifen treatment include those with a five-year projected breast cancer risk e1.66%, as calculated by the National Cancer Institute Breast Cancer Risk Assessment Tool, as well as those with lobular carcinoma in situ.
This risk assessment tool is available at the National Cancer Institute's risk calculator page.
The guideline notes that the benefit of taking tamoxifen for more than five years is unknown, and that the greatest clinical benefit has been demonstrated in premenopausal women, ages 35 to 50, who are unlikely to experience adverse events such as thromboembolic sequelae or uterine cancer.
Raloxifene has been shown to be as effective as tamoxifen for reduction in risk of invasive, but not noninvasive, breast cancer. In one trial it was associated with a significantly lower risk of thromboembolic events, benign uterine disorders, and cataracts.
Neither drug has been shown to reduce overall or breast-cancer specific mortality; the trials thus far have not been powered to demonstrate this.
The guideline urges clinicians to give careful consideration to risks and benefits, and discuss them in detail with women at risk.
"Women taking these drugs will need to consider both the benefits and adverse effects of each agent," Dr. Visvanathan said in a press release.
"It is important for women who are considering taking tamoxifen or raloxifene to have this discussion with their health provider before deciding whether to take these drugs," she said.
The discussion should also address quality of life concerns, the authors said.
In one study that compared the two agents, patients taking tamoxifen experienced more gynecologic and vasomotor symptoms, leg cramps, and bladder control difficulties, while those on raloxifene had more musculoskeletal complaints, dyspareunia, and weight gain.
The update also emphasizes that risk assessment should be carried out periodically, because a woman's risk increases throughout her lifetime.
While the National Cancer Institute's tool is the most commonly used, other population-specific tools are available for risk assessment in women with a strong family history of breast cancer and for African-American women.
The guideline also addresses the issue of disparities in access to healthcare for minorities, noting that minority patients with cancer face substantial obstacles to care, are more likely to be uninsured, and are more likely to receive poor care.
"Awareness of these disparities should be considered in the context of this clinical practice guideline, and healthcare providers should strive to deliver the highest level of care to these vulnerable populations," the guideline says.
Future efforts in reducing risks for breast cancer include ongoing trials evaluating aromatase inhibitors, further investigation of the synthetic steroid tibolone, and studies of preventive agents such as retinoids for ER-negative cancers.
Several members of the update committee disclosed consultant or advisory roles to a number of pharmaceutical companies, as well as receipt of honoraria and research funding.
Primary source: Journal of Clinical Oncology Source reference: Visvanathan K, 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" J Clin Oncol 2009; DOI: 10.1200/JCO.2008.20.5179.
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