Study: Switching Breast Cancer Drugs during Treatment Could Increase Survival (dateline April 30, 2007)
Switching from the drug tamoxifen to Aromasin (generic name, exemestane) two to three years after treatment could decrease a woman's risk of dying from breast cancer, according to the results of a recent study. Many women are treated with the drug tamoxifen for breast cancer. Aromasin is a different type of breast cancer drug that has been used for years to treat advanced breast cancer. Recently, researchers have found that Aromasin might be beneficial for early stage breast cancer too. The current research shows that the use of Aromasin after tamoxifen reduces the risk of death by 50% compared to 33% among women taking tamoxifen only.
"Tamoxifen has already saved the lives of many breast cancer patients," said lead researcher Professor Charles Coombes, director of the Cancer Research UK Laboratories and head of cancer medicine at Imperial College London, in a Cancer Research UK news release. "Our latest research shows that we can build on that success by treating women first with tamoxifen then switching to the new drug, Aromasin."
Tamoxifen (brand name, Nolvadex) has been the most commonly prescribed drug to treat breast cancer since its approval by the U.S. Food and Drug Administration (FDA) in the 1970s. Tamoxifen is an anti-estrogen and works by competing with the hormone estrogen to bind to estrogen receptors in breast cancer cells. By blocking estrogen in the breast, tamoxifen helps slow the growth and reproduction of breast cancer cells. In 1998, tamoxifen became the first drug to be approved by the FDA to prevent breast cancer after research showed it reduced the chances of developing breast cancer by 50% in women at high risk for the disease.
Aromasin is a different type of breast cancer drug. It was FDA-approved in 1999 to treat advanced (metastatic) breast cancer in post-menopausal women. Aromasin works by binding to the body's aromastase enzyme, an enzyme responsible for producing estrogen. Once Aromasin has binded to the aromastase enzyme, estrogen cannot be produced by the enzyme. This lack of estrogen "starves" cancer cells, preventing them from growing.
To determine whether Aromasin, given after tamoxifen, increases breast cancer survival, British researchers compared 2,372 women who took tamoxifen for five years with 2,352 women who switched to Aromasin after two or three years of taking tamoxifen. The researchers found that treating women with tamoxifen reduces the death rate by around 33% while treating women with tamoxifen then switching to Aromasin reduces the death rate by around 50%. Their results were published in the February 17, 2007 issue of The Lancet.
"This is the first time any hormone treatment has been shown to reduce the death rate more than tamoxifen alone," said Professor Coombes, in a Cancer Research UK news release. "Switching drugs also seems to avoid the side-effects of long-term tamoxifen therapy, such as cancer of the womb and deep vein thrombosis."
Common side effects of tamoxifen include hot flashes, irregular menstrual cycles, unusual vaginal discharge or bleeding, irritation of skin around vagina. Less common but potentially serious effects of tamoxifen also include"
Aromasin is also associated with side effects, most commonly hot flashes, nausea, fatigue, increased sweating, and increased appetite.
"These results are really very encouraging because they suggest that a sequence of tamoxifen and Aromasin could help reduce breast cancer deaths," said Cancer Research UK's medical director Professor John Toy in the charity's news release.