Raloxifene and Tamoxifen Help Prevent Breast Cancer, Confirms Study Conducted in Part by UAMS

By David Robinson

An update of the results of the Study of Raloxifene and Tamoxifen, (STAR P-2 trial in breast cancer prevention) shows that the drug raloxifene (initially used to prevent and treat osteoporosis in postmenopausal women) improved its effectiveness against noninvasive breast cancer, caused significantly less endometrial cancer and was significantly less toxic than tamoxifen. After 81 months of follow-up, although raloxifene was slightly less effective against invasive breast cancer, it still maintained strong efficacy.

The UAMS Cancer Institute participated in the STAR Study, one of the largest breast cancer prevention clinical trials ever conducted. STAR enrolled 19,490 postmenopausal women who were at increased risk for the disease in the follow-up study. A total of 57 women were enrolled at UAMS.

“We are encouraged by the results of this study and were pleased to a part of this national effort to study the effectiveness of these drugs on breast cancer prevention,” said V. Suzanne Klimberg, M.D., chief of the Division of Breast Surgical Oncology at UAMS and a professor in the Departments of Surgery and Pathology. She also is director of the Breast Cancer Program at the UAMS Cancer Institute.

This long-term trial is coordinated by the National Surgical Adjuvant Breast and Bowel Project (NSABP), a network of cancer research professionals, and is sponsored by the National Cancer Institute, part of the National Institutes of Health.

Participants were randomly assigned to receive either 60 mg of raloxifene (Evista®) (9,754 participants) or 20 mg of tamoxifen (Nolvadex®) (9,736 participants) daily. The 81-month study results (versus the 47 months in the initially published report) show that raloxifene retained 76 percent of the effectiveness in preventing invasive disease and grew closer to tamoxifen in preventing noninvasive disease, while remaining less toxic. The relative effects of the drugs in the longer term are more consistent with expected profiles, including greater potency of tamoxifen in preventing invasive and noninvasive disease, and, significantly, less endometrial toxicity with raloxifene.

“These results help clarify that both raloxifene and tamoxifen are good preventive choices for high risk postmenopausal women depending largely on a woman’s risk factors,” said Norman Wolmark, M.D., NSABP Chairman. “The results of this longer-term study should encourage wide spread acceptance of raloxifene and greater acceptance of tamoxifen for breast cancer prevention among postmenopausal women at an elevated risk, ultimately reducing the burden of breast cancer on the public health.”

Improved detection and treatment of breast cancer have not eliminated the need for better prevention of this disease, which accounted for approximately 192,000 new cancer cases and 40,000 cancer deaths in the United States in 2009.

Although the selective estrogen-receptor modulator (SERM) tamoxifen became the first U.S. Food and Drug Administration (FDA)-approved agent for reducing breast cancer risk, it did not gain wide acceptance for prevention largely because it increased endometrial cancer and thromboembolic events.

Raloxifene was approved by the FDA for breast cancer risk reduction following its pronounced efficacy in preventing invasive, but not noninvasive, breast cancer in the Phase III Study of Tamoxifen and Raloxifene. Initial STAR toxicity profiles favored raloxifene (e.g. significantly reduced thromboembolic events and, non-significantly, reduced endometrial cancer) over tamoxifen. Differences in the two drugs made it imperative to conduct longer-term follow-up to clarify their relative merits in regard to a host of benefits and risks, but particularly in regard to noninvasive breast cancer.

STAR participants were postmenopausal, at least 35 years old, and had a modified breast cancer risk as determined by their age, family history of breast cancer, personal medical history, age of first menstrual period, and age at first live birth. Eligible women were randomly assigned to receive either tamoxifen or raloxifene daily for five years. Before participating in the study, women were instructed about the potential risks and benefits of tamoxifen and raloxifene, and then were asked to sign an informed consent document.

A STAR investigator today presented additional data from the long-term Study at the 101st Annual Meeting of the American Association for Cancer Research (AACR) in Washington, D.C. These results will be published simultaneously in Cancer Prevention Research, a journal of the American Association for Cancer Research. A video podcast will be available in the near future.

The makers of tamoxifen, AstraZeneca Pharmaceuticals of Wilmington, Del., and the maker of raloxifene, Eli Lilly and Company of Indianapolis, provided their drugs and matching placebos for the trial without charge to participants. Eli Lilly and Co. also gave NSABP support to defray recruitment costs at the participating centers and to help local investigators conduct the study. For tools used to calculate a woman’s risk for breast cancer, visit http://cancer.gov/bcrisktool.

UAMS is the state’s only comprehensive academic health center, with colleges of Medicine, Nursing, Pharmacy, Health Related Professions and Public Health; a graduate school; a 540,000-square-foot hospital; six centers of excellence and a statewide network of regional centers. UAMS has 2,775 students and 748 medical residents. Its centers of excellence include the Winthrop P. Rockefeller Cancer Institute, the Jackson T. Stephens Spine & Neurosciences Institute, the Myeloma Institute for Research and Therapy, the Harvey & Bernice Jones Eye Institute, the Psychiatric Research Institute and the Donald W. Reynolds Institute on Aging. It is the state’s largest public employer with more than 10,000 employees, including nearly 1,150 physicians who provide medical care to patients at UAMS, Arkansas Children’s Hospital, the VA Medical Center and UAMS’ Area Health Education Centers throughout the state. Visit www.uams.edu or uamshealth.com.