Study of Tamoxifen and Raloxifene (STAR)

The Study of Tamoxifen and Raloxifene, or STAR, was a clinical trial that began at an estimated 500 sites across the United States, Puerto Rico, and Canada early in 1999. Participants in STAR included more than 19,000 postmenopausal women who were at increased risk for breast cancer. They were given a drug that could reduce their chances of developing breast cancer.

STAR built on the success of the Breast Cancer Prevention Trial, which showed that high-risk women taking the drug tamoxifen for an average of 4 years had a 49% reduced chance of developing breast cancer.

STAR was designed to help determine whether raloxifene (Evista), a drug similar to tamoxifen, was as effective as tamoxifen in reducing the chance of developing breast cancer in women who have not had the disease, and whether the drug had benefits over tamoxifen, such as fewer side effects. Raloxifene was first approved by the FDA as an osteoporosis prevention drug for postmenopausal women.

Study results showed that both tamoxifen and raloxifene lowered the risk of developing invasive breast cancer by about 50%. Also, the women who took raloxifene daily and were followed for around 4 years had 36% fewer uterine cancers and 29% fewer blood clots than the women who were on tamoxifen.

Women chosen to participate in STAR were age 35 or older, postmenopausal, and had an increased risk of breast cancer as determined by their age, family history of breast cancer, personal medical history, age at first menstrual period, and age at first live birth. They were randomly assigned to receive either tamoxifen daily or raloxifene daily for 5 years. They received close follow-up examinations, including mammograms, physical examinations, and gynecologic examinations, on a regular basis for at least 7 years.

Researchers with the National Surgical Adjuvant Breast and Bowel Project conducted the trial, which was funded by the National Cancer Institute. They selected the institutions to participate in STAR, including sites in 48 states, 6 Canadian provinces, the District of Columbia, and Puerto Rico.

STAR began enrolling participants in 1999 and completed enrollment in 2004. The trial concluded in 2006. The results of the STAR trial showed that regular use of raloxifene works as well as tamoxifen at reducing breast cancer risk in postmenopausal women who are at high risk, but appears less likely to cause some of the potentially dangerous side effects seen with tamoxifen use, such as an increase in uterine cancer and blood clots in the lungs and major veins.