In 1998, the US Food and Drug Administration (FDA) approved the drug tamoxifen (Nolvadex) to reduce the risk of breast cancer in women at high risk (those whose risk of developing breast cancer over the next five years is 1.67% or greater). Tamoxifen can significantly reduce the risk of breast cancer over a five-year period. But tamoxifen also increases the risk of potentially life-threatening side effects, including thromboembolism (blood clots) and endometrial cancer . Also, because tamoxifen prevents so-called “estrogen receptor-positive” breast cancers, women who take tamoxifen and still develop breast cancer are more likely to develop estrogen receptor-negative cancer, which has a worse prognosis.

In research based on a mathematical model to be published in the September 1, 2006 issue of Cancer , researchers attempted to determine how tamoxifen, given as a cancer-prevention drug, affects life expectancy, and whether or not it is cost-effective. According to their model, the researchers found that tamoxifen does not increase life expectancy for most women considered high-risk for breast cancer, and that the cancer-prevention strategy costs as much as $1.3 million per year of life saved.

About the Study

The researchers created a mathematical model to calculate mortality risk and cost-effectiveness associated with tamoxifen use, based on a hypothetical group of 50-year-old women at high risk for breast cancer. They tracked the health outcomes, life expectancies, and medical costs of these hypothetical women, assuming that some did and others did not take tamoxifen to reduce their risk of breast cancer. The researchers used data from published studies and statistics to calculate the risks of death, breast cancer, endometrial cancer, or any other adverse effect associated with tamoxifen. Costs associated with taking the drug, hospitalizations, laboratory tests, and other relevant factors were calculated based on current prices in the United States.

The researchers found no significant difference in life expectancy among women with a 1.67% five-year risk of breast cancer who did and did not take tamoxifen. For these women, the cost of tamoxifen was $1.3 million per year of life saved. Tamoxifen did not begin to increase life expectancy until a woman’s five-year risk of breast cancer was 3% or more.

This study is limited by the fact that it was based on a mathematical model, not actual long-term outcomes of women who have taken tamoxifen to reduce breast cancer.

How Does This Affect You?

This study found that only a small percentage of women who are currently offered tamoxifen as a cancer-prevention drug actually experience an increase in life expectancy.

For many women, the increased risks of endometrial cancer and estrogen receptor-negative breast cancer associated with tamoxifen outweigh its ability to prevent estrogen receptor-positive breast cancer. Women at high risk for breast cancer should talk to their physicians to determine their individual risks and benefits from taking this drug.

Although it may seem insensitive to put a price on life, costs do factor into medical policy. One way to make tamoxifen more cost-effective might be to target it to women who have had a hysterectomy and therefore are not at risk for endometrial cancer. Raloxifene (Evista) is another drug that has recently been shown to reduce the risk of breast cancer, but with fewer side effects. This drug might be a more cost-effective alternative to tamoxifen.

Finally, more studies must be done to determine how tamoxifen affects quality of life—a factor certainly to be extremely important to women weighing the pros and cons of starting a preventive drug therapy.