* Since the study lasted only four years, is tamoxifen really preventing breast cancer, or simply delaying it? Previous studies indicate that prolonged use of the drug (10 years) increases the risk of developing breast cancer.
* Who should take it for prevention? High-risk women are typically defined as those who have a mother, sister or daughter with breast cancer. But there are several other risk factors (such as never having borne a child), and there is debate over which of those factors would constitute sufficient risk to consider drug therapies to prevent the disease.
Study Not Geared to Address Race
In addition, the recently halted study did not include enough nonwhite women to know whether the effect is similar for women of all races.
"There are still a lot of questions," Love says. "Is it just subduing breast cancer? Tamoxifen is not the prevention drug. It probably reduces the risk of breast cancer short-term."
The National Cancer Institute recently released a computer program for doctors that will help them determine whether a particular patient is a candidate for preventive medications. Called the Breast Cancer Risk Assessment Tool, the program estimates a woman's risk in the following five years and over her lifetime.
But since the FDA has not yet approved tamoxifen for prevention, physicians may be reluctant to administer it, Love says.
"I think most physicians are still feeling very confused about who should be on it," she says.
And consumers, too, are apt to be perplexed by the intense publicity surrounding the tamoxifen prevention study and the many issues it raised. According to Fran Visco, president of the National Breast Cancer Coalition, an advocacy organization, one caller to her office wondered whether it was OK to give tamoxifen to her 12-year-old daughter.
"The attention this trial has gotten concerns us," Visco says.
However, others say that the value of tamoxifen for cancer prevention is established despite the unresolved issues.
Balancing One Set of Risks Against Another
"Women whose breast cancer risk is sufficiently high to offset the potential detrimental effects of tamoxifen would be candidates for the drug. However, women whose breast cancer risk is not as high should evaluate their individual benefits and risks with their physicians in order to make an informed decision with regard to the use of tamoxifen," stated the authors of the study, in a recent Journal of the National Cancer Institute.
Complicating the prevention question is the information, released in May, that a drug called raloxifene may also prevent breast cancer. The FDA approved raloxifene, which is sold under the brand name Evista, several years ago for the prevention of osteoporosis. But a study found that postmenopausal women taking the medication reduced their risk of breast cancer by about 70% without the serious side effects seen with tamoxifen use.
However, the study had followed the women for only two years, considered a very short time to assess a medication's long-term impact.
"People are being put on raloxifene for breast cancer assuming that this is perfectly fine," says Love. "But we have no information on that. These prevention drugs are still really up in the air."
While tamoxifen was tested on women as young as 35 with a high risk of breast cancer, raloxifene was studied only on older women with average to low risk of breast cancer.
An important new study, the Study of Tamoxifen and Raloxifene, will begin early next year to compare medications in preventing breast cancer. About 22,000 high-risk, postmenopausal women will be recruited at 193 institutions nationwide and in Canada. The women will be given either 20 milligrams of tamoxifen or 60 milligrams of raloxifene daily for five years.
Perhaps the best thing about the trove of new information on breast cancer is where it will lead in the years to come, experts note.
"We have a better sense of how to focus those research dollars that are so hard to get," Visco says. "We are at the next level of cancer research."
Want to Know More?
For more information on emerging news, studies and information on breast cancer:
* Health professionals who wish to order the Breast Cancer Risk Assessment Tool can call the NCI's Cancer Information Service at (800) 4-CANCER or visit the NCI Web site at http://cancertrials.nci.nih.gov.
* Women interested in participating in the Study of Tamoxifen and Raloxifene can obtain information at http://www.nsabp.pitt.edu; or by mail to NSABP, Box 21, Pittsburgh, PA 15261. Or fax: (412) 330-4660.
Local participating study investigating groups include Cedars-Sinai Medical Center, City of Hope National Medical Center in Duarte, Los Angeles Oncologic Institute, San Gabriel Valley Clinical Oncology Research Program in Pasadena, St. Mary Medical Center in Long Beach, UCLA Cancer Prevention Network at UCLA, UC Irvine Medical Center in Orange and USC/Norris Comprehensive Cancer Center.
* The National Alliance of Breast Cancer Organizations is offering additional information this month including an expanded online calendar listing year-round meetings and events and a national survey on women's attitudes about breast biopsy. Call (888) 80-NABCO or visit http://www.nabco.org.