Use of tamoxifen divides the experts
While leading cancer researchers are suggesting that 2 million U.S. women are good candidates for tamoxifen to reduce their risk of breast cancer, some doctors and consumer health advocates are questioning the soundness of that advice. Because the drug is known to raise the risk of uterine cancer, stroke and blood clots, they caution that women should wait to begin such therapy until more is known about the medication’s long-term effects.
Women in their 40s and 50s, in particular, may already be skeptical of the notion of healthy people taking a pill to prevent cancer after last year’s news that hormone replacement therapy not only fails to protect people from heart disease but also likely puts them at greater risk.
The breast cancer analysis released last week from the National Cancer Institute suggests that the benefits of taking tamoxifen to prevent breast cancer outweigh the potential risks for millions of women, especially white women ages 40 to 59. The researchers found that the risks of tamoxifen therapy rise as women age. Black women also have more reason to be careful of tamoxifen because they have a higher risk for blood clots.
Tamoxifen is considered an effective therapy for preventing the recurrence of breast cancer. In 1998, the Food and Drug Administration also OKd the drug for healthy women at high risk of getting the disease. The decision was based on the Breast Cancer Prevention Trial in which 175 women taking a placebo, or ineffective dummy pill, developed breast cancer, contrasted with 89 women who took tamoxifen.
But sales of the drug indicate that tamoxifen is not popular for prevention. According to the leading manufacturer of the drug, AstraZeneca, about 600,000 women a year take tamoxifen, most of whom have already developed breast cancer.
It is unclear why there is such a large discrepancy between the millions of women who experts say could clearly benefit from preventive use of tamoxifen and those actually taking it for that purpose. One explanation is that some doctors and patient advocates believe there are too many unanswered questions about tamoxifen.
“Anything that encourages healthy women to take tamoxifen with the information we have now is not a good thing,” said Fran Visco, president of the National Breast Cancer Coalition, a patient advocacy group. “We don’t actually know if taking tamoxifen in healthy women saves lives. We don’t know, if a woman takes tamoxifen for risk reduction, when is the best time to take it.” Doctors have known for several years that tamoxifen can help prevent breast cancer. The National Cancer Institute report is important because it provides data to demonstrate how many women in various age and ethnic groups could benefit from tamoxifen treatment.
Breast cancer prevention efforts should focus on approaches besides drug therapies, said Barbara Brenner, executive director of Breast Cancer Action, a patient advocacy group. “The notion that we’re going to find [prevention] in a pill is an illusion and misleads the public,” she said. “The general public understands prevention is something you do to keep you from getting sick. This isn’t prevention. There is no guarantee that this won’t make you sick. This is disease substitution.”
The Breast Cancer Prevention Trial was stopped more than a year ahead of schedule when researchers discovered that women taking tamoxifen were benefiting significantly, compared with the placebo group. Researchers will continue to track those women’s progress to learn more about the long-term risks and benefits of tamoxifen, said Andrew Freedman, a cancer institute epidemiologist and lead author of the new report.
“Eventually,” he said, “we will have a better idea of whether taking it longer means more benefit or more risk.”
Official recommendations for who should take tamoxifen may not help clarify matters for women. In a report released last summer, the U.S. Preventive Services Task Force said there was “fair evidence” that tamoxifen “improves health outcomes.” The federally sponsored independent panel concluded that the benefits of the drug outweighed the harm for women at high risk of breast cancer. It suggested that women at low or normal risk of the disease avoid the drug.
Even the study published last week in the Journal of the National Cancer Institute stops short of encouraging greater use of tamoxifen, despite estimating that 28,492 cases of breast cancer could be avoided or deferred if all 2.4 million women likely to benefit from tamoxifen took the drug for five years.
Some doctors may be reluctant to recommend tamoxifen because the actual risk of a particular woman developing the disease, even among the highest-risk groups, may still be only 2%, said Dr. Clifford Hudis, chief of the breast cancer medical service at Memorial Sloan-Kettering Medical Center in New York City. Among those women, 1% could be expected to develop breast cancer anyway.
But Dr. Worta McCaskill-Stevens, a co-author of the report, said too few women understand their breast cancer risk and tamoxifen’s potential benefit. The risk factors for breast cancer include advancing age, a family history of the disease, a history of atypical hyperplasia on a breast biopsy, beginning menstruation at an early age, having never given birth or being older at first birth.
“We want women to be informed,” said the institute researcher. “I think this provides a tool and, hopefully, it will become more widely disseminated than it is at this time.”
Dr. Beth Karlan, director of the Women’s Cancer Research Institute at Cedars-Sinai Medical Center in Los Angeles, notes that the study is based on a research model that doesn’t take into account individual health outcomes.
Even so, Karlan said, the study is based on sound science and serves to “drive home the point” to women that there are actions they can take to help reduce their cancer risk.
