MONDAY, April 11, 2005 (HealthDay News) -- Even though the drug tamoxifen has proven effective in preventing breast cancer, a new survey finds fewer than one in five women at high risk for the disease say they would take the medication.
Fears regarding potential side effects and the perception that their breast cancer risk is actually low were the main reasons given, said lead researcher Dr. Joy Melnikow, a professor of family and community medicine at the University of California, Davis.
"I was surprised at the relatively low percent of women interested in taking it," said Melnikow. "I expected the women to be more fearful of breast cancer."
Reporting in the online April 11 issue of Cancer, Melnikow and her team interviewed 255 women, all eligible to receive tamoxifen as a preventive drug due to their high estimated five-year risk of getting breast cancer. That risk was calculated by a computer model that combined factors such as a woman's age, whether a first-degree family member (such as a mother) had had breast cancer, and other factors. If a woman's risk rose to 1.66 or above, she was considered eligible for preventive tamoxifen therapy, the researchers explained.
The estimated mean five-year breast cancer risk among the 255 women interviewed in the survey was 2.8. After an educational session that explained tamoxifen's potential risks and benefits, 45 women -- just 17.6 percent -- said they would be inclined to take the drug on a regular basis to help prevent breast tumors. Women at very high estimated risk of beast cancer (with scores of 3.5 or above) were no more likely to say they would take it than women with lower risk, Melnikow noted.
The California researcher said it's unclear why so many at-risk individuals balk at taking tamoxifen, but she suspects many women have by now seen friends get breast cancer and survive. "They didn't see it as a death sentence," she said.
"Our own point of view [in doing the study] was to try to understand how women made informed decisions about this," she said.
What is clear, she said, is that "the willingness to accept risks for a drug taken for preventive purpose is different" than a drug to treat an existing disease or condition.
Tamoxifen works to reduce breast cancer risk by blocking the cancer-promoting effects of circulating estrogen.
When asked about their decisions, women who said they would not be inclined to take tamoxifen most often cited concern about the increased risk of blood clots in the lungs, Melnikow said. Other areas of concern were the risk of sexual dysfunction and the increased risk of cataracts.
Deciding to take or not take a drug for preventive purposes, Melnikow said, seems to be a very individual decision. "A woman needs to look at the risks and benefits," she said.
Women seemed confused about their own level of risk for breast cancer as well, Melnikow added. For example, even though many women said they wouldn't consider tamoxifen use, many also overestimated their risk -- perceiving themselves at ten times their actual risk. On the other hand, when asked to describe their risk as low, average or high, most said "low" or "average."
The study results, which echo findings from previous research, came as no surprise to other experts.
"There's not all that much new here," said Debbie Saslow, director of breast and gynecologic cancer control for the American Cancer Society. "This study went a bit further" by asking women for reasons, she noted.
One weakness of the study, she said, is that it was conducted in a research setting, not a clinical setting, where a trusted doctor who knows an individual woman's history explains the pros and cons of taking tamoxifen preventively.
This means that "what these women say may not reflect what they will ultimately do," Saslow said.
The bottom line, said Dr. Ann Partridge, a medical oncologist and clinical researcher at Dana-Farber Cancer Institute, in Boston, is that "people feel differently about taking medicine to treat a disease they have and others they could get."
To learn more about tamoxifen, visit the American Cancer Society.