According to results recently presented at the 2006 annual meeting of the European Society for Medical Oncology (ESMO), the addition of Herceptin® (trastuzumab) to Arimidex® (anastrozole) improves progression-free survival among patients with HER2-positive and hormone-positive advanced breast cancer.
The majority of breast cancers are hormone-positive, which means they are stimulated to grow from exposure to the female hormones estrogen and/or progesterone. Women with hormone-positive breast cancers are treated with agents that reduce or prevent these hormones from stimulating growth of the cancer cells.
Arimidex is a commonly used aromatase agent; aromatase agents are newer forms of hormone therapy for women with hormone-positive breast cancer.
The human epidermal growth factor 2 (HER2) is a protein that is often overexpressed in breast cancer cells. HER2 is involved in the growth and spread of cancer cells. Cancers that overexpress HER2 are referred to as HER2-positive.
Herceptin is a monoclonal antibody that is targeted against the HER2 protein. Herceptin stops or slows the spread of HER2-positive cancer cells.
Researchers recently conducted a phase III clinical trial directly comparing Herceptin plus Arimidex to Arimidex alone as initial therapy for advanced, HER2-positive, hormone-positive breast cancer.
This trial included postmenopausal women. Approximately half the participants were treated with Herceptin/Arimidex and half who were treated with Arimidex only. Patients treated with Arimidex only were allowed to “cross over” and begin treatment with Herceptin/Arimidex if their cancer progressed. Patients were permitted to receive one previous hormone therapy regimen before the trial began.
- Anticancer responses occurred in 20.3% of patients treated with Herceptin/Arimidex, compared with only 6.8% of patients treated with Arimidex only.
- Half of the patients treated with Herceptin/Arimidex did not experience progression of their cancer at nearly five months, compared with only 2.4 months for those treated with Arimidex only.
- Overall survival was improved by approximately five months among patients initially treated with Herceptin/Arimidex, despite the fact that more than half the patients treated with Arimidex only had crossed over to receive the combination therapy.
The researchers concluded that the addition of Herceptin to Arimidex significantly improves progression-free survival while demonstrating a trend toward improved overall survival compared with Arimidex only in the treatment of postmenopausal, HER2-positive, hormone-positive breast cancer.
Reference: Roche. Herceptin Added to Hormonal Therapy Increases Progression-Free Survival in Patients with Advanced HER2-Positive Breast Cancer. Available at: http://www.roche.com/home/media/med_div/med_div_pharma/med-div-2006-10-02b.htm. Accessed October 2006.
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