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Tamoxifen is the most commonly used drug to treat breast cancer, but new research suggests that another drug, Femara, may help decrease the risk of a breast cancer recurrence in women who have already taken tamoxifen. The study found that Femara, generic name letrozole, reduce the risk that breast cancer would return in women by about 63 percent, if the women first completed a five-year regimen of tamoxifen. The research sheds light on another treatment that could help successfully fight breast cancer. Tamoxifen, the most highly prescribed drug to treat breast cancer, belongs to a class of drugs called SERMS (estrogen receptor modulators). SERMS are "anti-estrogens" and work by competing with estrogen to bind to estrogen receptors in cancer cells. By blocking estrogen in the breast, tamoxifen helps slow the growth and reproduction of breast cancer cells. In addition to treating breast cancer, tamoxifen is also used to prevent breast cancer in women determined to be at high-risk of developing the disease. Femara is a different type of drug, an aromatase inhibitor. These drugs work by binding to the body's aromastase enzyme, an enzyme responsible for producing estrogen. Once the aromatase inhibitor has binded to the aromastase enzyme, estrogen cannot be produced by the enzyme. This lack of estrogen starves cancer cells, preventing them from growing and dividing. Femara was recently approved by the U.S. Food and Drug Administration (FDA) as an initial treatment option in advanced breast cancer patients after data showed that Femara may work better than tamoxifen in some patients (i.e., slowed the growth of cancer and improved survival time). To conduct the current study, researcher Paul Goss of Massachusetts General Hospital and his colleagues studied post-menopausal women who had been diagnosed with breast cancer and treated one to seven years previously. The women had already been treated for five years with tamoxifen. Many women are treated with tamoxifen for up to five years to reduce the risk that breast cancer will return after initial treatments, such as surgery, radiation, and/or chemotherapy. The results of the study showed that taking Femara after five years of tamoxifen reduced the risk that breast cancer would spread to other organs by 61 percent. It also reduced the risk that the women would develop breast cancer in their other, unaffected breast, by more than 80 percent. The researchers say that while their study investigated only Femara, they believe that the results may be similar for other aromatase inhibitors, such as Aromasin (generic name, exemestane), Arimidex (generic name, anastrozole), or Megace (generic name, megestrol). Further research is needed to confirm these findings. Possible side effects of Femara include:
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