According to results recently presented at the 2006 annual San Antonio Breast Cancer Symposium, the combination of Herceptin® (trastuzumab) and Arimidex® (anastrozole) results in better survival without cancer progression than Arimidex alone in women with metastatic, HER2-positive, hormone-dependent breast cancer.
Twenty to thirty percent of breast cancers overexpress (make too much of) a protein known as HER2. Overexpression of this protein leads to increased growth of cancer cells and a worse breast cancer prognosis. Herceptin is an agent that recognizes and binds to HER2-positive cells. The effects of Herceptin are thought to include decreased cell growth and increased cell death.
Arimidex is a type of drug known as an aromatase inhibitor. Aromatase inhibitors block the production of estrogen in tissues outside of the ovaries and reduce estrogen levels in postmenopausal women. This reduction in estrogen levels may slow or stop the growth of breast cancers that are responsive to estrogen (estrogen receptor-positive).
Studies have indicated that approximately 45%–50% of all HER2-positive breast cancers are also estrogen receptor-positive. Therefore, researchers speculated that the combination of agents that target both biologic pathways, such as Herceptin and Arimidex, may improve outcomes compared to a single agent in this group of patients.
Researchers from several institutions around the world conducted a Phase III trial, referred to as the TAnDEM study, to directly compare Herceptin plus Arimidex to Arimidex alone in the treatment of HER2-positive, hormone-dependent, metastatic breast cancer. This trial included 207 postmenopausal women.
Women were assigned to receive either Arimidex plus Herceptin or Arimidex alone. Women who were initially assigned to receive Arimidex alone were allowed to receive Arimidex plus Herceptin if their cancer worsened.
- A reduction in detectable cancer occurred in 20% of women who were initially treated with Arimidex plus Herceptin, compared to 7% of women who were initially treated with Arimidex alone.
- Cancer worsened in 4.8 months in women treated with Arimidex plus Herceptin, compared to 2.4 months in women treated with Arimidex alone.
- Overall survival was 28.5 months for patients treated with Arimidex plus Herceptin, compared with 23.9 months for those treated with Arimidex alone.
- Among patients without liver metastasis (cancer that had spread to the liver), overall survival was 41.9 months for patients treated with Arimidex plus Herceptin, compared with 32.1 months for those treated with Arimidex alone.
- Patients treated with Arimidex plus Herceptin were more likely to experience heart problems than patients treated with Arimidex alone; however, only one patient treated with Arimidex plus Herceptin experienced symptoms of heart failure.
The researchers concluded that Arimidex plus Herceptin improves survival without cancer progression among patients with HER2-positive, hormone-positive, metastatic breast cancer. Additional research is necessary to compare concurrent administration of these drugs (administration of both drugs at the same time) to sequential administration (administration of one after the other).
Reference: Mackey J, Kaufman B, Clemens M, et al. Trastuzumab prolongs progression-free survival in hormone-dependent and HER2-positive metastatic breast cancer. Proceedings from the 2006 annual San Antonio Breast Cancer Symposium. December 2006. Abstract #3.
Related News:Improved Progression-free Survival in Advanced Breast Cancer with Addition of Herceptin® to Arimidex® (10/11/2006)
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