MONDAY, July 24, 2006 (HealthDay News) -- Women at risk for breast cancer or breast cancer recurrence are routinely prescribed tamoxifen to help lower that risk, but a new study suggests the drug will not boost the life expectancy of many women who take it.
Specifically, women at high risk for breast cancer but without any prior history of the disease may not benefit from use of the drug in terms of extended life span, researchers found.
They also found the drug to be extraordinarily expensive from a public policy point of view, costing up to $1.3 million per year of life saved.
"If someone was on the lower end of the risk threshold, I would say the benefits of taking tamoxifen in terms of mortality are not there," said lead researcher Dr. Joy Melnikow, professor of family and community medicine at the University of California Davis, Sacramento.
Her team published its findings Monday in the Sept. 1 issue of the journal Cancer.
First approved in 1998 by the U.S. Food and Drug Administration to help prevent breast cancer in women at high risk for the disease, "Tamoxifen [brand named Nolvadex] has been around a long time," Melnikow explained.
The drug works by interfering with the activity of the hormone estrogen, thus reducing the chances of developing breast cancer. The FDA's approval for preventive use was aimed at women with at least a 1.67 percent chance of developing the disease over the next five years -- the threshold for "high risk." The average 60-year-old white woman carries this level of risk, Melnikow said.
The new analysis tackled an as yet unanswered question: Whether tamoxifen does, in fact, lower death rates for high-risk women who take it to prevent breast cancer.
To calculate the drug's effectiveness, Melnikow's team developed a mathematical model that followed a hypothetical group of 50-year-old women to an endpoint of death or 100 years of age.
The researchers reported that tamoxifen would only extend life expectancy when a woman's five-year risk of developing breast cancer reaches about 3 percent or more.
"If women are near that threshold [of 1.67 percent], at the lower end of the high-risk range, the effect of tamoxifen on mortality from breast cancer and overall [causes] was extremely small or negligible," Melnikow said.
And tamoxifen is not without its own level of risk. While reducing the chance that a woman at high risk will get breast cancer, the drug can also increase her risk of developing endometrial cancer, cataracts and blood clots.
Melnikow emphasized that the new analysis is only looking at death rates in women at high risk of breast cancer who do not have it -- not for women with a prior history of the disease.
"We know in women who have had breast cancer and have hormone-positive [tumors], taking tamoxifen improves their survival," Melnikow said. And, she added, it's well known that tamoxifen reduces breast cancer recurrence in women who had breast cancer by 47 percent with five years of treatment. "It's also been proved to reduce the incidence of breast cancer in women at high risk" by about 49 percent, she said.
However, "We took into consideration the fact that the breast cancers that are prevented by tamoxifen are mostly hormone receptor-positive cancer, and those cancers actually have a better prognosis than hormone-receptor negative cancers," Melnikow explained.
In other words, even though the drug may help prevent many cases of more curable hormone receptor-positive cancers, it is not effective in protecting against more deadly receptor-negative tumors. Added to that is the raised risk for endometrial cancer and blood clots among women taking tamoxifen. The end result is no difference in mortality for many high-risk women using the drug, the researchers concluded.
Meanwhile, the mathematical model found that the drug cost as much as $1.3 million per year of life saved, based on the U.S. price of the drug. That's a concern not only for public policy makers, she said, but also for individual women. For example, a patient living in the Sacramento area can expect to pay between $240 and $1,500 per year for tamoxifen.
The bottom line: "For most women, they don't think it is going to help improve survival," said Dr. Herman Kattlove, medical editor for the American Cancer Society who is familiar with the analysis. "If you are in the [high range] of the high-risk group, it may help survival. But 'may' is the operative word." The drug does decrease the chance of getting breast cancer, he added.
"Risk does matter," stressed Dr. Christy Russell, associate professor of medicine at the University of Southern California Keck School of Medicine, Los Angeles, and an American Cancer Society spokeswoman. "Women at the higher [end of] the risk range are more likely to benefit from the tamoxifen, in terms of reducing their risk of dying prematurely from breast cancer," she said.
And even among lower-risk women, she said, "It would be more acceptable to use tamoxifen if she had no uterus, because a lot of the concern about potential deaths revolved around uterine cancer."
More information
There's help with calculating breast cancer risk at the U.S. National Cancer Institute.
