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What is tamoxifen?
The drug tamoxifen has been used for more than 30 years to treat patients with breast cancer. Tamoxifen works against breast cancer, in part, by interfering with the activity of estrogen, a female hormone that promotes the growth of breast cancer cells.
In October 1998, the U.S. Food and Drug Administration (FDA) approved tamoxifen to reduce breast cancer incidence in women at high risk for the disease. This decision was based on the results of the Breast Cancer Prevention Trial (BCPT).
The BCPT studied more than 13,000 pre- and postmenopausal high-risk women age 35 and older who took either tamoxifen or a placebo (an inactive pill that looked like tamoxifen) for up to 5 years. The BCPT also showed that tamoxifen works like estrogen to preserve bone strength, decreasing fractures of the hip, wrist and spine in the women who took the drug.
What is raloxifene?
The drug raloxifene was approved by the FDA in December 1997 for the prevention of osteoporosis in postmenopausal women. In October 1999, the FDA approved it as an osteoporosis treatment.
Raloxifene was studied in STAR after large studies testing its effectiveness against osteoporosis showed that women taking the drug developed fewer breast cancers than women taking a placebo. One of these studies was the Multiple Outcomes of Raloxifene Evaluation (MORE) trial.
The MORE trial was designed to study the effects of raloxifene on osteoporosis in postmenopausal women. Researchers also tracked rates of breast cancer. They observed a reduction in breast cancer risk among the women who took raloxifene.
Who participated in STAR?
Women at increased risk for developing breast cancer, who had gone through menopause and were at least 35 years old, participated in STAR. STAR began enrolling participants in 1999. Enrollment was closed on November 4, 2004, with 19,747 women recruited.
All STAR participants had to have an increased risk of breast cancer equivalent to or greater than that of an average 60- to 64-year-old woman. In that age group, 1.66% of women"or about 17 of every 1,000 women"would be expected to develop breast cancer within 5 years. The average risk of breast cancer in the women who chose to enter STAR was twice as high as this minimum risk.
What factors were used to determine increased risk for breast cancer for the participants?
A woman's risk of developing breast cancer is determined by many factors. The factors that most affect a woman's risk of the disease are:
- Number of first-degree relatives (mother, daughters or sisters) diagnosed with breast cancer
- Whether a woman has had any children and her age at her first delivery
- The number of breast biopsies a woman has undergone, especially if the tissue showed a condition known as atypical hyperplasia
- The woman's age at her first menstrual period
- The woman's age when she reached menopause
STAR researchers used the Breast Cancer Risk Assessment Tool to estimate a woman's risk of breast cancer using most of the above factors. The tool was developed by scientists at the National Cancer Institute and the National Surgical Adjuvant Breast and Bowel Project (NSABP).
What are the side effects of tamoxifen and raloxifene?
The known, serious side effects of tamoxifen are uterine cancer, blood clots, strokes and cataracts. Other side effects of tamoxifen include menopause-like symptoms such as hot flashes and vaginal discharge or bleeding.
Raloxifene has not been studied as long as tamoxifen. One of the goals of STAR was to better assess the drug's long-term effects. The known, serious side effect of raloxifene is blood clots. Other side effects include menopause-like symptoms such as hot flashes and vaginal dryness as well as joint pain or leg cramps.
What determined which participants received tamoxifen or raloxifene?
Participants in STAR were randomized (assigned by chance) to receive either tamoxifen or raloxifene. In a process known as "double blinding," neither the participant nor health caregivers knew which pill she was receiving. Setting up a study in this way allows researchers to directly compare the true benefits and side effects of each drug without the influence of other factors.
All women in the study were scheduled to take 2 pills a day for 5 years: half took active tamoxifen and a raloxifene placebo (an inactive pill that looks like raloxifene); the other half took active raloxifene and a tamoxifen placebo (an inactive pill that looks like tamoxifen). All women received 1 of the active drugs; no one in STAR received only the placebo. The dosages are 20 mg of tamoxifen and 60 mg of raloxifene per day.
What do the participants do now that the results are known?
All the women in STAR are being asked to continue their follow-up examinations according to the study protocol. Women who were randomly assigned to the raloxifene group and who have not completed 5 years of taking the drug will be able to continue on that drug.
Women who were randomly assigned to the tamoxifen group had the option of completing their 5 years of tamoxifen or switching to raloxifene for the remainder of their 5 years.
Why won't the women who took tamoxifen in STAR now take 5 years of raloxifene?
There is no evidence that taking more than 5 years of either drug will further reduce a woman's chance of developing breast cancer.
Should postmenopausal women at increased risk of breast cancer take raloxifene based on these results?
Both tamoxifen and raloxifene are FDA-approved drug for the reduction of breast cancer risk. Tamoxifen is approved for pre- and postmenopausal women and raloxifene is approved for postmenopausal women only.
Raloxifene is only FDA-approved for the prevention and treatment of osteoporosis as well as for the reduction of breast cancer risk in postmenopausal women. Postmenopausal women who are at increased risk of breast cancer can now consider taking either raloxifene or tamoxifen to reduce their risk.
As with any medical procedure or intervention, the decision to take one of these drugs is a personal one. Even if a woman is at increased risk of breast cancer, raloxifene or tamoxifen therapy may not be right for her. Women who are considering breast cancer prevention therapy should talk with their health care provider.
What can premenopausal women at increased risk of breast cancer do to reduce their breast cancer risk?
Tamoxifen has already been shown to reduce a premenopausal woman's risk of developing breast cancer by half in the Breast Cancer Prevention Trial. The drug is FDA-approved to reduce breast cancer risk in premenopausal women. In the BCPT, women under age 50 did not have an increased risk of the most serious side effects seen with tamoxifen use: uterine cancer, blood clots, strokes and cataracts. Premenopausal women at increased risk of breast cancer can discuss tamoxifen therapy as an option with their physicians. Raloxifene is not FDA-approved for use in premenopausal women.
Are there women who should not take raloxifene?
Raloxifene is not FDA-approved for use in premenopausal women for any indication. It is approved for the prevention and treatment of osteoporosis as well as for the reduction of breast cancer risk in postmenopausal women. Postmenopausal women with a history of blood clots, hypertension, diabetes and cigarette smoking must also consider that raloxifene increases the risk of serious blood clots.
How much did the STAR study cost?
To date, the National Cancer Institute has spent $88 million through peer-reviewed grants to the NSABP to support STAR. In addition, Eli Lilly and Company, Inc., provided NSABP with $30 million to defray recruitment costs at the participating centers and to help local investigators conduct the study. The maker of tamoxifen, AstraZeneca Pharmaceuticals, Inc., Wilmington, Del., and the maker of raloxifene, Eli Lilly and Company, Indianapolis, Ind., provided their drugs and matching placebos for the trial without charge to participants.
What is the National Surgical Adjuvant Breast and Bowel Project?
The NSABP is a cooperative group funded by the National Cancer Institute with a 50-year history of designing and conducting clinical trials. The results of these trials have changed the way breast cancer is treated and, now, prevented. They were the first to demonstrate on a large scale the prevention effects of the drug tamoxifen in breast cancer.