MONDAY, June 5, 2006 (HealthDay News) -- The osteoporosis drug raloxifene is as effective as the cancer drug tamoxifen in reducing the risk of invasive breast cancer in postmenopausal women, new research shows.
But the two drugs vary in "side-effect profiles," meaning each may be appropriate for a different set of women. This is somewhat at odds with previous proclamations, which had labeled raloxifene a "clear winner" over tamoxifen.
The latest results of the STAR (Study of Tamoxifen and Raloxifene) trial were announced Monday at the annual meeting of the American Society of Clinical Oncology, in Atlanta.
"Basically it's good news," said the study's lead author, Dr. D. Lawrence Wickerham, associate chairman of the National Surgical Adjuvant Breast and Bowel Project. "Postmenopausal women with an increased risk for breast cancer have a new and effective option for chemoprevention of invasive disease."
Dr. Robert Morgan, a medical oncologist with City of Hope Cancer Center in Duarte, Calif., added, "This is important data. Both are very excellent drugs."
Although tamoxifen has been on the market for 30 years and has a proven effect, many women and doctors have been hesitant to use the drug because of side effects, such as hot flashes, vaginal dryness, decreased sex drive and nausea.
Raloxifene is already used by 500,000 women for osteoporosis prevention and treatment. Although it is not yet approved to prevent breast cancer, experts hope gynecologists and primary-care physicians, who have experience with raloxifene, will start prescribing it for breast-cancer prevention.
"We would expect that the STAR results would increase the numbers taking the drug and decrease breast cancer occurring in the U.S. and around the world," Wickerham said. "The STAR results are an important next step in the elimination of breast cancer."
"It's obviously an important study. Not only does it add to our knowledge but it provides another option for women at high risk of getting breast cancer to consider," added Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "If it gets more women into a prevention strategy, then that's good news. It's important that both women and their physicians recognize that a preventive strategy is available, and it's important for women and their physicians to have conversations with each other to determine which approach is best for them."
The STAR trial enrolled almost 20,000 postmenopausal women with an increased risk for breast cancer. Participants were randomly selected to take either 20 milligrams of tamoxifen or 60 milligrams of raloxifene daily for five years.
Both drugs reduced the risk of breast cancer by about 50 percent, to about four per 1,000 women a year, from eight per 1,000 women per year.
However, raloxifene was not as effective in preventing non-invasive breast cancers as tamoxifen. "This is biologically intriguing, but we haven't been able to define this," Wickerham said.
Women on tamoxifen had more uterine cancers, blood clots and cataracts. There were no significant differences with regard to the incidence of other cancers, heart problems, stroke, bone fracture or death, the study found.
The STAR findings were also released online Monday in the Journal of the American Medical Association, and will appear in the journal's June 21 print issue.
Another report released Monday at the ASCO meeting that was culled from STAR data found that quality of life, based on both mental and physical indicators, was about the same between women in the raloxifene group and those in the tamoxifen group.
There was slightly greater decline in sexual function among women in the tamoxifen group, particularly younger women.
"It was a very subtle, statistically significant difference, but whether it is clinically significant and meaningful is hard to say," said Dr. Patricia A. Ganz, the study's lead author and director of the Division of Cancer Prevention and Control at the University of California, Los Angeles' Jonsson Comprehensive Cancer Center.
Tamoxifen seemed to do better in the areas of musculoskeletal pain, weight gain and painful intercourse, while raloxifene came out ahead in vasomotor symptoms, leg cramps and gynecological symptoms, the study found.
"We now have two equally effective drugs to be used in preventing breast cancer," Ganz said. "We can start woman on one drug and if, after three months, she's having a symptom that she feels is not tolerable, we can switch to the other drug. But we want women to be able to take a drug to prevent or reduce incidence of breast cancer. It does us no good if she doesn't take the medication."
More information
For more on the STAR trial, visit the U.S. National Cancer Institute.
