Few women take tamoxifen to prevent breast cancer

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Andrew N. Freedman, Ph.D.

Erika A. Waters, Ph.D.

Researchers with the National Cancer Institute (NCI) have found that the prevalence of tamoxifen use for the prevention of breast cancer among women without a personal history of breast cancer is very low. Tamoxifen can reduce the risk of developing breast cancer in women who are at increased risk for developing the disease. Details of this survey are published in the February issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

The low prevalence of tamoxifen use may stem from various sources, which were not investigated in this study, according to the study's coauthor Andrew N. Freedman, Ph.D., chief of the Clinical and Translational Epidemiology Branch, Division of Cancer Control and Population Sciences, NCI.

However, he stressed that "counseling individual women about using tamoxifen to prevent breast cancer must include a patient's discussion with her physician about the drug's risks and benefits, as well as consideration of the patient's personal values, preferences, lifestyle and specific medical situation."

Lead author of this study Erika A. Waters, Ph.D., M.P.H., assistant professor at Washington University School of Medicine in St. Louis, and colleagues at the NCI wanted to gain an understanding of how many women aged 40 to 79 years were taking tamoxifen for the prevention of breast cancer. They answered this question using data from the National Health Interview Surveys from years 2000 and 2005, which are nationwide surveys designed to be representative of the entire United States. The surveys included more than 10,000 women for each year.

"Our results indicated that very few women were using tamoxifen to prevent breast cancer," said Waters. "However, we don't know exactly why."

The researchers found that the prevalence of tamoxifen use in this survey population was very low — 0.2 percent in 2000 and 0.08 percent in 2005. The difference between the two years was not statistically meaningful, according to the researchers.

Freedman and Waters speculated that the drug's low uptake may be linked to many factors including the fact that tamoxifen is associated with several side effects. These side effects include hot flashes, sexual problems, uterine cancer, blood clots and cataracts. Other possible explanations that the researchers gave for the low uptake may be that physicians are unaware of the drug's availability, physicians are reluctant to prescribe it, patients are reluctant to take it, there is a lack of patient or physician education about the drug, or skepticism about whether the benefits outweigh the risks. It could also be that physicians and patients are, in fact, very educated and are making very informed decisions, according to the researchers.

"The decision to use a drug like tamoxifen in women at high-risk for, but who do not yet have a diagnosis of breast cancer is not easy. It is dependent upon the woman's personal choice, which can be influenced by many factors, not just her medical eligibility. There is no right answer," said Waters, who at the time of the study was a fellow in the Cancer Prevention Fellowship Program, Center for Cancer Training, NCI.

Susan Gapstur, Ph.D., M.P.H., vice president of epidemiology, American Cancer Society, and editorial board member of Cancer Epidemiology, Biomarkers & Prevention, said that "overall, these results provide an important snapshot of the very low uptake of tamoxifen for cancer prevention."

"Although the researchers speculate on a number of possible explanations, it remains unclear to what extent the low uptake might be attributed to physician reluctance to prescribe tamoxifen and/or patient reluctance to take it," said Gapstur.

Source: American Association for Cancer Research