According to the results of a study published in the Journal of the National Cancer Institute, use of aromatase inhibitors in postmenopausal women with advanced breast cancer results in better survival than use of other standard hormonal therapies.
A majority of breast cancers are estrogen receptor-positive (ER-positive), meaning that they are stimulated to grow by the female hormone estrogen. Depriving ER-positive breast cancers of estrogen can slow the growth of these cancers.
For many years tamoxifen has been a mainstay of hormonal therapy for breast cancer. Tamoxifen acts by blocking estrogen receptors. More recently, however, drugs known as aromatase inhibitors have produced promising results.
In premenopausal women, the ovaries are the major source of estrogen. After menopause, when ovarian hormone production drops dramatically, some estrogen continues to be produced in tissues outside of the ovaries. In this process, androgens produced by the adrenal glands are converted into estrogen. An enzyme called aromatase is required for this conversion. Aromatase inhibitors block the activity of aromatase and stop the conversion of androgens to estrogen. This lowers estrogen levels in postmenopausal women.
To summarize the available evidence about the benefits of aromatase inhibitors in the treatment of advanced breast cancer, researchers conducted a combined analysis of previously published studies. These studies included a total of 8,504 women with metastatic or inoperable locally advanced or recurrent breast cancer.
- More recently introduced aromatase inhibitors or inactivators, such as Arimidex® (anastrozole), Aromasin® (exemestane), and Femara® (letrozole), reduced risk of death by 13% compared to standard hormonal therapy.
- Aromatase inhibitors improved survival when compared to tamoxifen in the initial treatment of advanced breast cancer, and also improved survival when compared to other hormonal therapies in subsequent courses of treatment.
The researchers conclude that compared to other standard hormonal treatments, aromatase inhibitors improve survival in postmenopausal women with advanced breast cancer.
Reference: Mauri D, Pavlidis N, Polyzos NP, Ioannidis JPA. Survival with Aromatase Inhibitors and Inactivators Versus Standard Hormonal Therapy in Advanced Breast Cancer: Meta-analysis. Journal of the National Cancer Institute. 2006;98:1285-91.